CERN Is Forcing Scientists to Rethink Reality_s Rules _ Science For Sleep

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At 5.52 in the morning on June 27th, 2026, the
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last protons in the Large Hadron Collider completed their final
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loop through 27 kilometers of underground tunnel beneath the Swiss-French border,
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and the most powerful particle accelerator ever built went quiet.
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No alarm sounded. No ceremony marked the moment. A number
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on a monitoring dashboard ticked to zero. and the beams
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that had been circling at nearly the speed of light
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simply stopped. The control room staff noted the time in
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a log. For most of the world, it was an
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ordinary Friday morning. For the people who had spent careers building, running,
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and analyzing data from that machine, it was something harder
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to name. The Large Hadron Collider had been running in
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some form since 2008. three separate data-taking runs. More than
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a decade of proton collisions at energies no previous machine
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had reached. The numbers from Run 3 alone are almost
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meaningless in ordinary terms. 125.4 inverse femtobarns of integrated luminosity,
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the largest data set a particle collider had ever produced
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in a single operational period. To translate that into something human,
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hundreds of billions of individual collision events, each one a
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tiny controlled explosion at the scale of atomic nuclei, each
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one producing sprays of particles that detect as the size
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of apartment buildings recorded in fractions of a second. What
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physicists were looking for in all of that data was
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something that didn't fit. That is not a metaphor for
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open-minded science. It is the literal goal. The standard model
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of particle physics, the theoretical framework assembled over roughly 50 years,
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finalized in something close to its current form by the mid-1970s,
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tells physicists exactly what should come out of those collisions.
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Every known particle, every known force, The model is precise
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enough that its predictions and the measurements from experiments agree
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to ten decimal places in some cases. That level of
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agreement is almost unreasonable. It is one of the most
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tested and confirmed theories in the history of science. If
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you find comfort in these gentle explorations of space and science,
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I'd be grateful if you'd consider subscribing and giving this
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video a like. I'd love to know where you're watching
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from and what time it is for you. Feel free
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to drop your location and time in the comments below.
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And it is not enough. Not because it is wrong, exactly.
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Because it is incomplete in ways that are too large
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to ignore. The Standard Model says nothing about dark matter.
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which appears to make up roughly 27% of the universe.
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It says nothing about dark energy, which appears to drive
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the accelerating expansion of space and accounts for another 68%.
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It cannot incorporate gravity into its framework at all. Add
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those gaps together and the most successful theory in particle
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physics describes, at best, about 5% of what actually exists.
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For 50 years, physicists have known this. The question was
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always where the cracks would appear first. The LHC was
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built in part to find them. What made the shutdown
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of June 27th different from a routine pause was not
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just the scale of the data collected. It was what
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the data contained. Over three runs, The machine had been
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producing results that sat in an uncomfortable position. Not clean confirmations,
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not clean refutations, but signals. Measurements that drifted away from
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standard model predictions by amounts too large to dismiss easily
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and too small, so far, to declare a discovery. Particles
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that shouldn't exist in the configurations they were found in.
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decay patterns that didn't match the model's arithmetic, asymmetries between
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matter and antimatter that pointed somewhere the theory couldn't follow.
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None of this made headlines the way the Higgs boson
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did in 2012. A hint of new physics buried in
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a statistical distribution is harder to explain than a particle
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with a name. But the physicists tracking these results were
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not treating them as noise, They were treating them as clues.
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Something was nudging the data in a consistent direction, and
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the standard model offered no explanation for what that something was.
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This is where physics stands right now. Not at a
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moment of collapse. The standard model still works, still predicts,
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still matches experiment across an enormous range of measurements with
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extraordinary precision. But at the edges of what it can describe,
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The seams are showing. Measurements that should agree with the
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theory don't. Quite. Particles are appearing that require explanations. The
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theory isn't built to give. The machine that spent 15
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years probing these edges has now gone offline. It's tunnel sealed.
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It's magnets warming up for the first time in years.
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And the data it left behind is still being analysed
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by thousands of researchers at institutions across dozens of countries.
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The questions that data is meant to answer are not small.
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Why does matter exist? What is the 95% of the
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universe the Standard Model cannot see? Why do certain particles
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decay the way they do when the equations say they shouldn't?
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Is there a deeper framework underneath the one physicists have built?
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Something that would explain the Standard Model the way the
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Standard Model explains the behaviour of atoms? These are not
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rhetorical questions. They have specific, measurable answers, and the LHC
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was designed to find them. Whether it succeeded and how,
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and what exactly was sitting in the data that nobody expected,
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That is a longer story. What the machine had found
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over three runs and more than a decade of collisions
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was not nothing. And understanding what it actually means requires
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starting from the beginning. The standard model of particle physics
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is one of the most successful scientific theories ever written,
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which makes its blind spots all the more disturbing. To
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understand what the standard model actually is, Start with a
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simple idea. Everything around you, the chair, the air, your
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own hands, is made of particles. Not just atoms, but
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things smaller than atoms. And those particles do not simply
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float in space doing nothing. They push and pull on
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each other through forces. The standard model is the theory
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that names all of these particles describes all of those
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forces in a single coherent framework. It took physicists roughly
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four decades to build it, from the late 1920s through
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the early 1970s, assembling piece by piece through experiments, arguments,
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and mathematical predictions that turned out to be right in
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ways that still seem almost unreasonable. The particle list runs deep. Quarks,
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which combine to form protons and neutrons. Electrons, which orbit
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atomic nuclei and make chemistry possible. Neutrinos, which pass through
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ordinary matter almost without interaction. Trillions of them are moving
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through your body right now. Photons, which carry light. Gluons,
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which hold quarks together with something called the strong force.
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the W and Z bosons which govern radioactive decay, and
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finally in 2012 the Higgs boson which had been predicted
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since 1964. Each of these was found. Each confirmed a prediction.
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The theory's track record is essentially unbroken across five decades
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of increasingly precise experimental tests. To get a sense of
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just how precise, Consider this. The standard model predicts the
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magnetic strength of the electron to 11 decimal places. When
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physicists actually measure it, the answer matches to 11 decimal places.
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That is not luck. That is a theory that is
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capturing something genuinely true about the structure of reality. No
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other scientific framework in history has made predictions accurate to
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that level and been right. By any reasonable measure, the
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standard model is a triumph. And yet, something is wrong.
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Not wrong in a small way, wrong in a way
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that sits quietly behind every conference paper and every seminar slide,
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like a door in the back of the room that
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nobody can open. The standard model describes particles and forces
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with extraordinary precision, but the universe contains things that the
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model simply does not see. Start with gravity. Gravity is
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not in the standard model. This sounds impossible given that
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gravity is the most obvious force in daily experience. Pull
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a book off a shelf and gravity is why it falls.
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Hold planets in orbit. shape galaxies, determine the large-scale structure
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of the universe. Gravity does all of this, and the
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Standard Model has nothing to say about it. Physicists have
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a separate framework for gravity, called General Relativity, and it
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works beautifully at the scale of planets and galaxies. But
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General Relativity and the Standard Model cannot be combined into
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a single consistent theory. At the smallest scales, where quantum
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mechanics dominates, gravity stops making sense. The two best theories
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in all of physics are fundamentally incompatible, and no one
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has resolved this. That is problem one. Problem two is darker,
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quite literally. Everywhere astronomers look, galaxies are spinning in ways
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they should not be able to. Stars on the outer
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edges of galaxies are moving far too fast. If the
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only matter in a galaxy were the matter you can see, stars, gas, dust,
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the gravity it generates would not be enough to hold
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those outer stars in orbit at that speed. They should
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fly off. They do not. Something is holding them in place.
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That something has gravitational pull. which means it has mass,
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which means it is matter. But it does not emit light.
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It does not absorb light. It does not interact with
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the particles in the standard model at all. Physicists call
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it dark matter, and it makes up roughly 27% of
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everything the universe contains. The standard model has no candidate
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for it. Not a single particle in the entire framework
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matches what dark matter appears to be. Then comes dark energy.
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In 1998, two independent teams measuring distant supernovae discovered something
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that genuinely shocked the physics community. The universe is not
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just expanding, it is expanding faster and faster. Something is
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pushing space itself outward with increasing force, working against gravity
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on the largest possible scale. That something is called dark energy,
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and it accounts for approximately 68% of the total energy
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content of the universe. The standard model does not describe it.
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The standard model does not predict it. The standard model
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cannot explain it. When physicists try to calculate what the
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energy of empty space should be based on quantum mechanics,
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they get a number that is off from the observed
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value by something in the range of 120 orders of magnitude,
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the largest discrepancy between theory and observation in the history
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of science. Add these numbers together and the picture sharpens
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into something unsettling. Dark energy is 68% of the universe.
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Dark matter is 27%. Everything else, every star, every planet,
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every atom ever measured, every particle the Standard Model accounts for,
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makes up the remaining 5%. The most precisely tested physical
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theory in history describes a small fraction of what actually exists.
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The Standard Model is not a map of the universe.
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It is a map of a small corner of it,
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drawn with extraordinary detail, surrounded on all sides by territory
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that remains completely blank. There is one more silence worth
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sitting with. The Big Bang, according to the best understanding
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of physics, should have produced equal amounts of matter and antimatter.
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When matter and antimatter meet, they annihilate. If the balance
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had been perfect, the universe would have destroyed itself in
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its first moments, leaving nothing behind but a faint glow
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of radiation. Instead, there are galaxies, there are stars, there
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are planets and oceans and people asking questions about the
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early universe. Something tipped the scale. one extra particle of
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matter for every billion matter-antimatter pairs was enough to leave
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everything we see. The Standard Model does allow for a
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small imbalance between matter and antimatter. Physicists call it CP violation,
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and this has been observed in certain particle decays. But
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the amount the model allows is far too small to
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account for the universe that actually exists. Something else caused
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the asymmetry. The standard model does not say what. All
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of this was known before the Large Hadron Collider ran
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its first collision. None of it is new. What changed
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over the course of three runs at CERN was not
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the discovery that the model was incomplete. That was already clear.
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What changed was where, specifically, the data started pulling away
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from the predictions. the cracks began to have addresses. Physicists
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had known for decades that the Standard Model was incomplete.
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They just did not know exactly where the cracks would
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start to show. On July 4th 2012, two independent experiments
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at CERN announced simultaneously that they had found it, the
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particle that physicists have been hunting for nearly half a century.
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The auditorium at CERN filled with applause Peter Higgs, the
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theorist who had proposed the particle's existence back in 1964,
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was sitting in the front rows. He wiped his eyes.
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Around the world, physicists who had spent careers building toward
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this moment stopped what they were doing. Some of them wept.
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This was not a small result. This was the last
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missing piece of the Standard Model. The particle that the
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entire theoretical architecture had predicted must exist, and which nobody
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had been able to confirm for 48 years. To understand
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why 2012 felt like a culmination, you have to understand
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what the Higgs boson actually does. The Standard Model describes
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particles and forces with remarkable precision, but there was a
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problem buried in its early versions. The mathematics worked only
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if certain particles had no mass at all. Photons fit
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that description, but electrons, quarks, and the W and Z
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bosons clearly do have mass. Something was giving them mass,
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and the theory had no mechanism to explain it. In 1964,
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Peter Higgs and several other physicists independently proposed a solution.
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They suggested that space itself is filled with a field
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now called the Higgs field, and that particles acquire mass
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by interacting with it. The stronger a particle's interaction with
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the Higgs field, the heavier it becomes. A particle with
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no interaction at all, like the photon, passes straight through
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without gaining any mass. The Higgs boson is the ripple
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in that field. It is what you detect when you
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disturb the field enough. For decades this was theoretical machinery, elegant, necessary,
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but unconfirmed. The Higgs boson was predicted to be heavy,
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somewhere above 100 billion electron volts in mass, which meant
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it required a machine powerful enough to produce it in collisions.
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The Large Hadron Collider was built, in large part, to
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find it. When the ATLAS and CMS detectors both registered
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a new particle at around 125 billion electron volts in
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the summer of 2012, the statistical significance was beyond any
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reasonable doubt. Five sigma from ATLAS, five sigma from CMS,
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two independent detectors, two independent teams, the same result. The
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Higgs boson was real. The mechanism was confirmed. The field
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that fills all of space and grants mass to matter
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had been proven to exist. Physicists celebrated, and they had
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every right to. This was a genuine triumph. The Standard
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Model had predicted the Higgs boson before the technology to
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find it even existed, and the prediction was correct. That
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kind of success is rare in science. The theory had
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been vindicated at its deepest level. For a brief period,
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It felt like the book might be closing on a
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chapter of physics that had begun in the 1960s. Then
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physicists started measuring the Higgs boson in detail. And the
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questions started. The first thing researchers wanted to know was
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whether the Higgs boson behaved exactly as the standard model predicted.
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The theory is specific. It says how often the Higgs
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should decay into each type of particle. and in what proportions.
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It says how strongly the Higgs should couple to fermions
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of different generations. Measuring these properties was not just a formality,
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it was a test. Any deviation from the predictions, even
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a small one, would be evidence that something beyond the
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standard model was influencing the Higgs behind the scenes. One
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decay mode drew particular attention. The Higgs boson can decay
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into a pair of muons. Muons are second generation particles,
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heavier cousins of the electron, but still relatively light compared
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to the top quark or the bottom quark. The standard
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model predicts that this decay should happen roughly once in
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every 5,000 Higgs decays. That is extraordinarily rare. Collecting enough
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of these events to say anything statistically meaningful requires enormous
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data sets and years of running time. Scientists at the
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ATLAS experiment eventually found compelling evidence that this decay was occurring.
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The numbers, roughly, match the prediction. But roughly is doing
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a lot of work in that sentence. The reason this
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particular decay matters so much is what it probes. The
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Higgs boson interacts most strongly with the heaviest particles. Its
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coupling to the top quark, the heaviest particle in the
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standard model, is enormous. Its coupling to the bottom quark
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is large enough to measure without much difficulty. But the
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muon is a second generation particle, much lighter, and its
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coupling to the Higgs is far weaker. Measuring that coupling
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tests whether the Higgs field interacts with different generations of
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matter in exactly the way the theory requires. Any deviation,
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even a subtle one, could mean that the Higgs is
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not quite the particle the standard model describes. It could
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mean something else is participating in the mass generation process.
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It could mean the theory is missing a layer. So far,
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the muon coupling measurement is consistent with the standard model.
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But consistent is not the same as confirmed. The uncertainty
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on that measurement is still large enough to hide significant deviations.
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As the LHC collected more data through run 3, the
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error bars on this number shrank. They have not yet
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shrunk enough to make a definitive statement. That work continues.
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Then there is the question of Higgs self-coupling. This is
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where the physics becomes genuinely unsettling. The standard model predicts
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not just how the Higgs interacts with other particles, but
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how it interacts with itself. The Higgs field has a
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specific shape. Physicists call it the shape of the Higgs potential,
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and that shape determines the structure of the field that
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fills all of space. The self-coupling constant determines whether that
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potential looks the way the theory predicts. Measuring it requires
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observing two Higgs bosons produced together in the same collision,
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which is extraordinarily rare, far rarer than even the muon decay.
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The LHC has been collecting these events, but the statistics
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are still thin. The measurement has not yet been made
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with precision. What physicists have established is a range. The
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self-coupling is somewhere within a factor of a few of
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the standard model value. That is not good enough to
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confirm the theory. It is not good enough to break
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it either. Why does this matter? Because the shape of
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the Higgs potential is not just a detail. It describes
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how the Higgs field settled into its current state after
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the Big Bang. In the very early universe, the field
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was in a different configuration. As the universe cooled, it
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transitioned to its current state, giving mass to particles in
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the process. The precise shape of that potential determines whether
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this transition happened smoothly or violently, and whether the conditions
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in the very early universe were capable of producing the
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matter-antimatter asymmetry that allowed the universe to survive. If the
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self coupling deviates from the standard model prediction, it changes
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the picture of what happened in the first fractions of
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a second after the Big Bang. This is not an
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abstract point. It connects the particle measured in a detector
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to the reason anything exists at all. There is one
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more layer The Higgs boson is the only fundamental particle
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in the Standard Model with zero spin. Every other particle
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has some amount of angular momentum built into its quantum structure.
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The Higgs has none. It has no electric charge. It
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carries no colour charge, so the strong force ignores it.
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It is, in a sense, the quietest particle in the theory.
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the one that sits at the center and connects everything
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else by granting them mass while interacting as little as possible.
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This uniqueness makes its properties especially sensitive to the presence
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of new physics. Any additional particles or forces that couple
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to the Higgs, even weakly, would leave fingerprints on its
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decay rates and coupling strengths. The Higgs is, in this way,
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a precision instrument for detecting what the Standard Model cannot see.
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The decade following the 2012 discovery was not the quiet
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period of consolidation that some physicists expected. It was a
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decade of increasingly precise measurement, and each measurement sharpened the
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question of whether the Higgs was exactly what the theory said,
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or something slightly different. The answer, at the close of
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Run 3, that nothing is clearly broken but the precision
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required to make that statement keeps improving and the range
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of possible deviations keeps narrowing and within that narrowing range
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there is still room for something unexpected to be hiding
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the Higgs boson had been found confirmed and celebrated and
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then it started behaving in ways that raised more questions
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than it answered the word penguin does not belong in
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particle physics, and yet here we are. The name comes
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from a bar bet in the 1970s, a story too
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strange to be invented, involving a physicist who lost a
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wager and had to sign a paper with a penguin
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drawn on it. The diagram he was illustrating at the time,
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a particular kind of particle interaction drawn on a whiteboard,
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happened to look vaguely like the bird if you tilted
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your head at the right angle. The name stuck. Particle
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physics has not looked back. And while the name sounds
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like something from a children's book, what it describes is
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one of the most precise and troubling discrepancies in modern science.
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To understand why penguin decays matter, you first have to
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understand what a B meson is. A meson is a
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particle made of exactly two quarks, one quark and one
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antiquark bound tightly together by the strong force. B mesons
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are a specific family within that category, and what makes
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them interesting is that they contain a bottom quark. Bottom
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quarks are heavy, they are unstable. Left to themselves, they decay,
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transforming into lighter quarks and releasing energy in the process.
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The B-maison is essentially a clock that is always winding down.
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In the detectors at CERN, a B-maison lives for roughly
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a trillionth of a second before it falls apart into
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other particles. That is enough time, given how fast these
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particles move, to leave a detectable track. Physicists catch the
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wreckage and work backward to figure out what happened. Most
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of the time, B mesons decay in fairly ordinary ways.
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The bottom quark changes into a charm quark, releasing a
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W boson that quickly decays into lighter particles. This is
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a straightforward charged current interaction, well understood, well measured. The
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standard model predicts it cleanly and the data matches. There
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is no mystery there but there is another class of
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B meson decay that is far rarer and far stranger
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in these decays the bottom quark transforms not into a
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00:29:52.619 --> 00:29:56.900
charm quark but into a strange quark without emitting a
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W boson in the direct way Instead, the transformation happens
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through a quantum loop. The quark briefly emits and reabsorbs
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virtual particles, including a virtual top quark and a virtual
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W boson, before emerging as a strange quark. The loop
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itself releases a Z boson or a photon, which then
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decays into a pair of leptons, often two muons. This
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00:30:26.839 --> 00:30:30.480
is the penguin decay. It is named for the shape
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of that loop diagram on paper, and it happens only
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once in roughly every million B meson decays. That rarity
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is precisely why it matters. In the standard model, this
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process is suppressed. It happens, but it happens rarely, because
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the loop structure carries what physicists call a flavor-changing neutral current,
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A type of transition that the standard model actively disfavors.
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00:31:00.269 --> 00:31:03.890
The frequency and the angular distribution of the products are
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calculable in advance with high precision. When you measure the
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actual results in a detector and compare them to that calculation,
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the two numbers should match. If they do not match,
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something is interfering in that loop that the standard model
401
00:31:20.369 --> 00:31:26.130
does not account for. An undiscovered particle. an unknown force,
402
00:31:26.720 --> 00:31:30.720
something sitting in the quantum machinery of that decay that
403
00:31:30.759 --> 00:31:34.539
the current theory has no entry for. This is the
404
00:31:34.640 --> 00:31:38.359
thing that makes penguin decays so powerful as a probe.
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Because the standard model prediction is suppressed, any new physics
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00:31:43.380 --> 00:31:48.279
that couples to these quarks stands out. The signal-to-noise ratio,
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00:31:48.339 --> 00:31:51.519
in a sense, is favorable. You are looking for a
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ripple in quiet water. The LHCb experiment, built specifically to
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00:31:57.460 --> 00:32:02.619
study B meson decays with extraordinary precision, has been collecting
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00:32:02.660 --> 00:32:06.720
these events for over a decade. In runs spanning from
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2011 through the end of run 3, the collaboration recorded
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hundreds of billions of B meson decays. The penguin decays,
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by contrast, are counted in the thousands or tens of
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thousands rare events pulled from an enormous flood of more
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common ones. Extracting them requires isolating specific final states, a kaon,
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a pion, two muons, each with a measurable momentum and angle.
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The analysis involves mapping the full angular distribution of the
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decay products across multiple variables simultaneously. It is not a
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single number, it is a shape. A pattern in many
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dimensions that the standard model predicts in detail and that
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the detector measures in detail. When researchers published their measurements,
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the shape did not match. Not dramatically, not in a
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way that rewrote textbooks overnight, but in a consistent and
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repeating way across multiple variables and multiple data sets. The
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observed angular distributions leaned away from the predictions. The rate
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of certain configurations appeared suppressed relative to what the model expected.
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Each individual deviation was modest. Taken together across all the
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variables and all the data, the disagreement was significant enough
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to draw serious attention. Early results pointed to tensions in
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the range of 2 to 3 standard deviations from the prediction.
431
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In particle physics, 3 sigma is considered evidence. 5 sigma
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is a discovery. 2 to 3 sigma means something is
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worth investigating very carefully. What followed was years of careful investigations.
434
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Because in physics, a disagreement between theory and measurement can
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00:34:11.219 --> 00:34:15.059
mean several things. It can mean the measurement has a
436
00:34:15.159 --> 00:34:20.960
systematic error, a miscalibration of the detector, a background process
437
00:34:21.019 --> 00:34:25.889
being misidentified as signal. It can mean the theoretical prediction
438
00:34:25.989 --> 00:34:30.550
has an error. Hadronic effects, the messy influence of the
439
00:34:30.670 --> 00:34:35.469
strong force on these decays, are notoriously difficult to calculate.
440
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and introduce genuine uncertainty, or it can mean the standard
441
00:34:40.179 --> 00:34:42.860
model is wrong about what is happening in that loop.
442
00:34:43.539 --> 00:34:48.679
Ruling out the first two possibilities takes time and independent confirmation.
443
00:34:49.039 --> 00:34:54.760
Both take years. The hadronic uncertainty argument was taken seriously.
444
00:34:55.579 --> 00:34:59.719
Some theorists argued that strong force effects inside the B
445
00:34:59.760 --> 00:35:05.369
mesons Specifically, contributions from charm quarks running inside the loop
446
00:35:05.449 --> 00:35:09.469
in ways that are difficult to calculate precisely could shift
447
00:35:09.510 --> 00:35:13.900
the predictions enough to explain the discrepancy without new physics.
448
00:35:14.699 --> 00:35:18.480
This debate ran through the literature for several years. It
449
00:35:18.519 --> 00:35:22.539
has not been fully resolved, but the experimental side of
450
00:35:22.579 --> 00:35:28.179
the argument kept gaining weight. The LHCb collaboration updated their
451
00:35:28.239 --> 00:35:32.980
analysis with larger datasets. The measurements did not drift back
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toward the standard model prediction. They held. Other experiments running
453
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independently on different hardware with different systematic uncertainties looked at
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related observables. The discrepancies they found were consistent with what
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LHCb had seen. In 2022, The picture sharpened again. New
456
00:35:56.750 --> 00:36:02.090
electroweak penguin results from LHCb, using the full dataset from
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Run 2, showed deviations across a suite of angular observables.
458
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The combined tension had grown. Physicists who had been cautious
459
00:36:12.739 --> 00:36:15.699
began to speak more carefully about what the data was
460
00:36:15.920 --> 00:36:21.980
actually saying. The pattern of deviations across multiple observables was coherent.
461
00:36:22.599 --> 00:36:27.210
The same direction roughly the same magnitude in measurements that
462
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probe different combinations of the underlying physics. Random errors in
463
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a detector do not produce coherent deviations across many different
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00:36:36.909 --> 00:36:42.360
observables at once. Hadronic effects, while real and uncertain, do
465
00:36:42.400 --> 00:36:46.619
not generally produce this kind of structured disagreement across so
466
00:36:46.679 --> 00:36:53.389
many independent measurements simultaneously. Something systematic in the underlying physics
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00:36:53.510 --> 00:36:58.460
begins to look more plausible as an explanation. The theoretical
468
00:36:58.579 --> 00:37:02.420
frameworks for what that something might be have been accumulating
469
00:37:02.480 --> 00:37:06.920
for years. One popular class of models introduces a new
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particle called the Z-prime boson, a heavier cousin of the
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standard model Z-boson that couples preferentially to certain quarks and leptons.
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If a Z prime exists at a mass above what
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the LHC can produce directly, it would appear in these
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penguin loops as a virtual correction, subtly shifting the rates
475
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and distributions in exactly the pattern observed. The numbers from
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the B meson data, when used to constrain the properties
477
00:37:39.269 --> 00:37:43.409
of a hypothetical Z prime, point to a mass somewhere
478
00:37:43.469 --> 00:37:47.369
in the range of tens of ATV. far above the
479
00:37:47.429 --> 00:37:51.510
direct reach of RUM3, but potentially within the reach of
480
00:37:51.650 --> 00:37:58.260
future machines. Other frameworks invoke lepto-quarks, particles that carry both
481
00:37:58.380 --> 00:38:02.280
quark number and lepton number, and have no place in
482
00:38:02.320 --> 00:38:07.440
the current standard model. Some supersymmetric models generate the same
483
00:38:07.559 --> 00:38:12.539
kind of loop-level corrections through the exchange of virtual superpartners.
484
00:38:13.159 --> 00:38:17.389
No single theory fits perfectly. But the range of theories
485
00:38:17.449 --> 00:38:22.130
that can produce the observed deviations is significantly narrower than
486
00:38:22.190 --> 00:38:25.710
it was a decade ago, which is itself a result.
487
00:38:26.530 --> 00:38:30.730
What makes the penguin decay anomalies particularly compelling as a
488
00:38:30.769 --> 00:38:34.170
direction for new physics is that they appear in a
489
00:38:34.230 --> 00:38:38.800
part of the standard model that is genuinely calculable. The
490
00:38:38.880 --> 00:38:43.480
theory makes a precise prediction, not a rough estimate. The
491
00:38:43.519 --> 00:38:48.960
hadronic uncertainties, while real, are bounded by independent measurements and
492
00:38:49.099 --> 00:38:54.500
theoretical consistency checks. When the measurement sits outside that boundary,
493
00:38:54.820 --> 00:38:58.260
the argument for new physics in the loop becomes harder
494
00:38:58.320 --> 00:39:04.989
to dismiss. The data has been collected, recollected, cross-checked across experiments,
495
00:39:05.289 --> 00:39:10.170
and re-analysed with different methods. The numbers disagreed with the model,
496
00:39:10.449 --> 00:39:14.050
and the disagreement was too clean and too consistent to
497
00:39:14.110 --> 00:39:17.239
be a bad day in the data. The Big Bang
498
00:39:17.360 --> 00:39:21.420
created two kinds of matter in equal measure, and if
499
00:39:21.519 --> 00:39:26.250
physics had been perfectly symmetric that day, you would not exist,
500
00:39:26.989 --> 00:39:32.460
neither would anything else. No galaxies, no stars, no planets,
501
00:39:33.019 --> 00:39:37.360
no atoms floating in the cold dark between them. The
502
00:39:37.519 --> 00:39:41.739
universe would have produced equal quantities of matter and antimatter.
503
00:39:42.400 --> 00:39:45.969
Those two populations would have found each other. And in
504
00:39:46.010 --> 00:39:50.780
a cascade of mutual annihilation, Every particle would have been
505
00:39:50.880 --> 00:39:55.400
converted back into pure energy. What remains would be a
506
00:39:55.559 --> 00:40:01.059
featureless sea of photons, expanding forever through a universe that
507
00:40:01.119 --> 00:40:06.619
contains nothing. That is the logical endpoint of perfect symmetry.
508
00:40:07.170 --> 00:40:10.530
The fact that you are reading this means symmetry failed.
509
00:40:11.369 --> 00:40:16.650
Something went wrong. Or perhaps more precisely, something went right.
510
00:40:17.599 --> 00:40:22.099
at a scale so small it seems almost impossible. One
511
00:40:22.199 --> 00:40:27.949
extra particle of matter for every billion matter-antimatter pairs. That
512
00:40:28.030 --> 00:40:31.449
is the margin. Every galaxy you can see in the
513
00:40:31.510 --> 00:40:36.969
night sky, every cloud of gas, every rocky planet, every
514
00:40:37.179 --> 00:40:41.480
ocean and mountain range and living cell is the leftover
515
00:40:41.539 --> 00:40:45.659
from that tiny imbalance. The rest was annihilated in the
516
00:40:45.760 --> 00:40:49.480
first fractions of a second after the Big Bang. What
517
00:40:49.519 --> 00:40:53.340
we call the observable universe is a rounding error, and
518
00:40:53.380 --> 00:40:58.420
for decades, nobody could explain where that rounding error came from.
519
00:40:59.139 --> 00:41:02.900
The question has a name in physics. Actually, it has
520
00:41:03.000 --> 00:41:07.590
several names, but the one that matters here is baryogenesis.
521
00:41:08.300 --> 00:41:11.820
the process by which the early universe came to contain
522
00:41:11.929 --> 00:41:18.710
more baryons than antibaryons. Baryons are the heavy particles. Protons
523
00:41:18.769 --> 00:41:22.630
and neutrons are baryons. The atoms in your body are
524
00:41:22.690 --> 00:41:27.949
built from baryons. If baryogenesis had not happened, or had
525
00:41:28.110 --> 00:41:33.409
not happened asymmetrically, none of that exists. The Standard Model
526
00:41:33.510 --> 00:41:37.679
does acknowledge that such an asymmetry is required. What it
527
00:41:37.820 --> 00:41:42.099
cannot fully explain is how large that asymmetry should be,
528
00:41:42.119 --> 00:41:46.369
or whether the mechanisms it describes are powerful enough to
529
00:41:46.429 --> 00:41:50.670
account for the universe we actually observe. To produce a
530
00:41:50.789 --> 00:41:57.090
matter-dominated universe, three conditions have to be met simultaneously. The
531
00:41:57.170 --> 00:42:02.480
physicist Andrei Sakharov laid them out in 1967. One of
532
00:42:02.539 --> 00:42:06.929
those conditions is that matter and antimatter must behave differently
533
00:42:07.010 --> 00:42:12.730
under certain transformations. Not differently in a vague or approximate way,
534
00:42:13.369 --> 00:42:19.579
differently in a specific, measurable, precise way. Physicists call this
535
00:42:19.679 --> 00:42:24.699
CP violation, a breaking of the combined symmetry between charge
536
00:42:24.760 --> 00:42:28.889
and parity. If you reflect a particle interaction in a mirror,
537
00:42:29.380 --> 00:42:34.079
and swap every particle for its antiparticle, CP symmetry says
538
00:42:34.179 --> 00:42:38.900
the result should look identical. CP violation means it doesn't.
539
00:42:39.590 --> 00:42:43.429
The standard model does predict CP violation. It has been
540
00:42:43.489 --> 00:42:47.309
observed before, but the observations had been confined to a
541
00:42:47.349 --> 00:42:52.219
specific class of particles called mesons, composite particles made of
542
00:42:52.420 --> 00:42:56.820
one quark and one antiquark. Mesons are real and measurable,
543
00:42:57.030 --> 00:43:00.260
but they are not the building blocks of the visible universe.
544
00:43:00.869 --> 00:43:05.730
Protons and neutrons are. And protons and neutrons are baryons,
545
00:43:06.130 --> 00:43:11.289
not mesons. For years, CP violation had been confirmed in
546
00:43:11.329 --> 00:43:16.449
the meson sector without being directly confirmed in baryons. That
547
00:43:16.510 --> 00:43:21.010
distinction matters more than it might sound. Finding asymmetry in
548
00:43:21.090 --> 00:43:24.699
mesons is like finding asymmetry in the tools used to
549
00:43:24.739 --> 00:43:28.360
build a house. What you actually need to explain is
550
00:43:28.420 --> 00:43:33.260
the house. In 2019 and the years following, the LHCb
551
00:43:33.340 --> 00:43:37.969
experiment at CERN began producing results from a new analysis
552
00:43:38.030 --> 00:43:43.150
of baryon decays. The LHCb detector is built specifically to
553
00:43:43.210 --> 00:43:47.489
study particles containing beauty quarks, Its full name is the
554
00:43:47.550 --> 00:43:52.019
Large Hadron Collider Beauty Experiment, and it operates in the
555
00:43:52.139 --> 00:43:56.579
forward region of the collision zone, catching particles that fly
556
00:43:56.679 --> 00:44:00.900
out at shallow angles from the beam. That geometry gives
557
00:44:00.980 --> 00:44:05.480
it unusual sensitivity to the kinds of rare decays that
558
00:44:05.579 --> 00:44:10.989
carry signatures of CP violation. What the collaboration was hunting
559
00:44:11.090 --> 00:44:15.030
for was a difference in how baryons decay compared to
560
00:44:15.090 --> 00:44:20.989
how antibaryons decay. If matter and antimatter are truly symmetric,
561
00:44:21.510 --> 00:44:26.280
a baryon undergoing a particular decay should produce the same
562
00:44:26.510 --> 00:44:32.559
angular distribution of daughter particles as its antimatter counterpart. The
563
00:44:32.699 --> 00:44:39.380
same rates. The same patterns. Mirror images. CP violation means
564
00:44:39.460 --> 00:44:44.010
those mirrors are slightly distorted One set of decays happens
565
00:44:44.070 --> 00:44:48.150
just a little more often, or produces daughter particles at
566
00:44:48.309 --> 00:44:53.179
slightly different angles, or releases them with slightly different energies.
567
00:44:53.880 --> 00:44:58.840
The difference is small. Catching it requires enormous data sets
568
00:44:58.940 --> 00:45:05.150
and extremely precise detectors. The LHCb analysis combined data from
569
00:45:05.269 --> 00:45:11.349
multiple runs, studying hundreds of millions of baryon decays. The
570
00:45:11.389 --> 00:45:16.750
collaboration looked at how B-barians, particles containing a bottom quark
571
00:45:16.849 --> 00:45:22.179
bound with lighter quarks, broke apart into lighter particles. They
572
00:45:22.260 --> 00:45:27.420
measured the rates. They mapped the angular distributions. They compared
573
00:45:27.519 --> 00:45:31.250
matter to antimatter at each step. And they found it.
574
00:45:31.929 --> 00:45:36.690
The decays were not symmetric. Barians and antibarians were not
575
00:45:36.809 --> 00:45:40.900
behaving as mirrors of each other. The asymmetry was small,
576
00:45:41.219 --> 00:45:45.920
as expected, but it was there, and it was statistically robust.
577
00:45:46.840 --> 00:45:50.500
This was the first time CP violation had been confirmed
578
00:45:50.559 --> 00:45:53.949
in baryons with the statistical weight needed to call it
579
00:45:54.010 --> 00:45:58.429
an observation, rather than a hint. The precision of this
580
00:45:58.550 --> 00:46:04.769
measurement reflected the maturity of experimental particle physics. The LHCb
581
00:46:04.829 --> 00:46:10.719
team had to account for detector efficiencies backgrounds from competing processes,
582
00:46:11.400 --> 00:46:16.530
and the subtle ways particles interact with detector materials. They
583
00:46:16.590 --> 00:46:22.630
applied sophisticated statistical methods to extract genuine signals from noise.
584
00:46:23.329 --> 00:46:30.139
The analysis included exhaustive studies of systematic uncertainties, potential sources
585
00:46:30.199 --> 00:46:35.409
of bias that statistical methods alone cannot capture. Every major
586
00:46:35.469 --> 00:46:40.929
systematic had to be quantified and combined carefully. The collaboration
587
00:46:41.010 --> 00:46:46.780
produced auxiliary measurements to validate key assumptions. They cross-checked their
588
00:46:46.880 --> 00:46:54.119
findings using independent analysis strategies. Only when multiple approaches converged
589
00:46:54.179 --> 00:46:57.920
on the same answer could they claim confidence in the result.
590
00:46:58.610 --> 00:47:03.050
This is the standard modern particle physics demands before calling
591
00:47:03.150 --> 00:47:08.199
anything an observation. The significance of that result goes beyond
592
00:47:08.320 --> 00:47:11.460
adding a new entry to a catalogue. This is the
593
00:47:11.619 --> 00:47:16.300
first demonstration that the fundamental building blocks of atomic matter,
594
00:47:16.900 --> 00:47:20.960
the particles from which every proton and neutron is assembled,
595
00:47:21.539 --> 00:47:25.849
do not treat matter and antimatter identically. The universe is
596
00:47:26.010 --> 00:47:30.019
not symmetric at the level of baryons. That is not
597
00:47:30.079 --> 00:47:33.719
a minor finding. It is a confirmation that one of
598
00:47:33.840 --> 00:47:38.619
Sakharov's three conditions is physically real in the particle class
599
00:47:38.659 --> 00:47:42.400
that matters most for the existence of the visible universe.
600
00:47:43.139 --> 00:47:46.579
What the result does not do is close the problem.
601
00:47:47.320 --> 00:47:52.789
This is where things become genuinely difficult. CP violation in
602
00:47:52.889 --> 00:47:57.559
baryons exists. But the amount of CP violation that the
603
00:47:57.619 --> 00:48:02.199
standard model predicts across all the processes where it appears
604
00:48:02.599 --> 00:48:06.860
is far too small. The calculations have been done many
605
00:48:06.960 --> 00:48:11.340
times by many independent groups. They all converge on the
606
00:48:11.440 --> 00:48:17.349
same conclusion. The observed asymmetry between matter and antimatter Even
607
00:48:17.409 --> 00:48:20.929
when you add up every source the Standard Model contains
608
00:48:21.289 --> 00:48:25.610
is insufficient by many orders of magnitude to produce a
609
00:48:25.820 --> 00:48:30.000
universe with as much matter as ours. The imbalance that
610
00:48:30.039 --> 00:48:34.940
gave rise to everything we see required far more asymmetry
611
00:48:34.980 --> 00:48:38.260
than the model can generate. That gap is one of
612
00:48:38.320 --> 00:48:42.840
the most significant open problems in all of physics. It
613
00:48:42.940 --> 00:48:47.659
means one of two things. Either there are additional sources
614
00:48:47.719 --> 00:48:51.340
of CP violation that the standard model does not account
615
00:48:51.420 --> 00:48:58.230
for new particles, new interactions, new mechanisms operating at energies
616
00:48:58.309 --> 00:49:01.789
the LHC has not yet been able to reach or
617
00:49:01.829 --> 00:49:05.690
the model is missing something more fundamental about how the
618
00:49:05.789 --> 00:49:10.909
early universe evolved. Neither answer is satisfying in the sense
619
00:49:10.949 --> 00:49:15.119
of being available. Both require physics that has not been
620
00:49:15.179 --> 00:49:21.079
discovered yet. The LHCb confirmation of baryon CPU violation is
621
00:49:21.119 --> 00:49:24.780
a piece of the puzzle and a significant one. But
622
00:49:24.880 --> 00:49:29.119
identifying that the asymmetry is real in baryons is not
623
00:49:29.199 --> 00:49:33.519
the same as identifying its origin. The detection tells you
624
00:49:33.559 --> 00:49:37.239
the behavior exists. It does not tell you what is
625
00:49:37.380 --> 00:49:41.260
generating it at a level sufficient to populate the universe
626
00:49:41.320 --> 00:49:46.159
with matter. The measurement sits alongside the penguin decay anomalies,
627
00:49:46.860 --> 00:49:51.440
the Higgs coupling results, and the other discrepancies accumulating in
628
00:49:51.480 --> 00:49:56.260
the LHC data, all pointing in the same direction, all
629
00:49:56.320 --> 00:50:00.659
stopping short of a definitive answer. There is something almost
630
00:50:00.739 --> 00:50:05.230
vertiginous about the scale of what this implies. one extra
631
00:50:05.289 --> 00:50:10.039
particle per billion. That is the margin by which matter won.
632
00:50:11.019 --> 00:50:15.980
Every star in every galaxy, every cubic centimeter of gas
633
00:50:16.059 --> 00:50:20.380
in the interstellar medium, every atom in every human body,
634
00:50:21.219 --> 00:50:24.840
all of it descended from that margin. The physics that
635
00:50:24.940 --> 00:50:30.139
generated it operated in the first microseconds of the universe's existence,
636
00:50:30.889 --> 00:50:35.699
temperatures and densities that no laboratory can fully replicate and
637
00:50:35.780 --> 00:50:41.900
no equation is completely captured. The LHCb result confirms that
638
00:50:41.940 --> 00:50:45.920
the asymmetry is built into baryons at a measurable level.
639
00:50:46.559 --> 00:50:49.579
It does not explain why the universe survived at the
640
00:50:49.659 --> 00:50:54.690
scale it did. The asymmetry is real, confirmed and sitting
641
00:50:54.750 --> 00:50:57.829
in the data and it is still not large enough
642
00:50:57.889 --> 00:51:02.619
to explain why the universe survived. In the 1950s, particle
643
00:51:02.679 --> 00:51:06.329
physicists had a problem they called the particle zoo, and
644
00:51:06.389 --> 00:51:09.050
for a while it looked like nature was taunting them.
645
00:51:09.670 --> 00:51:12.510
Every few months a new particle turned up in a
646
00:51:12.550 --> 00:51:19.869
detector somewhere. Pions, kaons, lambda particles, sigma particles, Xi particles,
647
00:51:20.190 --> 00:51:24.340
the list kept growing. Each one was real, each one
648
00:51:24.380 --> 00:51:28.019
had been measured carefully and confirmed. and none of them
649
00:51:28.139 --> 00:51:33.719
fit into any clean organising principle. Physicists had built machines
650
00:51:33.800 --> 00:51:38.179
to find the fundamental building blocks of matter, and instead
651
00:51:38.679 --> 00:51:43.369
they were finding an ever-expanding catalogue of particles that seemed
652
00:51:43.550 --> 00:51:49.210
almost deliberately random. Enrico Fermi reportedly said that if he
653
00:51:49.250 --> 00:51:52.510
had wanted to memorise the names of all these particles,
654
00:51:53.050 --> 00:51:56.940
he would have gone into botany, The joke landed because
655
00:51:56.980 --> 00:52:00.989
it was also a genuine expression of frustration. There was
656
00:52:01.050 --> 00:52:05.309
no map. There was no framework. Just more animals in
657
00:52:05.349 --> 00:52:12.030
the zoo. Then, in 1964, Murray Gell-Mann and George Zweig
658
00:52:12.090 --> 00:52:17.150
independently proposed that all these hadrons were not fundamental at all.
659
00:52:17.829 --> 00:52:23.579
They were combinations of smaller objects, quarks. Protons and neutrons
660
00:52:23.619 --> 00:52:27.440
were made of three quarks each. The lighter mesons were
661
00:52:27.480 --> 00:52:32.599
made of two, one quark and one antiquark. Once you
662
00:52:32.659 --> 00:52:37.889
accepted that, the particle zoo made sense. The hundreds of
663
00:52:38.010 --> 00:52:43.409
strange particles were not random. They were predictable combinations of
664
00:52:43.449 --> 00:52:47.230
a small set of building blocks, following a small set
665
00:52:47.309 --> 00:52:52.130
of rules. The framework that eventually emerged from this insight
666
00:52:52.230 --> 00:52:58.469
became quantum chromodynamics. or QCD, the theory of how quarks
667
00:52:58.639 --> 00:53:02.760
bind together through a force carried by particles called gluons.
668
00:53:03.519 --> 00:53:08.960
The zoo was tamed. Physicists congratulated themselves and moved on.
669
00:53:09.639 --> 00:53:13.409
What they did not fully settle, even then, was whether
670
00:53:13.510 --> 00:53:16.789
quarks could only combine in groups of two or three.
671
00:53:17.530 --> 00:53:22.449
The theory did not strictly forbid larger combinations. A particle
672
00:53:22.550 --> 00:53:28.920
built from four quarks a tetraquark, was mathematically allowed. So
673
00:53:28.940 --> 00:53:34.480
was a five-quark particle, a pentaquark. Theorists pointed this out
674
00:53:34.579 --> 00:53:39.489
almost immediately after quarks were proposed. The prediction was made
675
00:53:39.550 --> 00:53:44.170
in the 1960s, sitting quietly in the literature for decades
676
00:53:44.250 --> 00:53:48.750
while experimental physics lacked the tools to confirm or rule
677
00:53:48.809 --> 00:53:54.010
it out. Finding a genuine tetraquark or pentaquark would require
678
00:53:54.110 --> 00:53:58.409
both enough collision energy to produce them and enough detector
679
00:53:58.449 --> 00:54:02.300
precision to identify them before they fell apart, which they
680
00:54:02.380 --> 00:54:07.460
do in extraordinarily short timescales, fractions of a fraction of
681
00:54:07.519 --> 00:54:13.239
a second. The exotic Hadron search occupied physicists for generations
682
00:54:13.300 --> 00:54:19.130
with limited success. The problem was fundamental. These particles are rare,
683
00:54:19.389 --> 00:54:23.949
fragile and fleeting. They materialize in the chaos of a
684
00:54:24.010 --> 00:54:29.760
collision and decay almost instantly into more stable products, leaving
685
00:54:29.820 --> 00:54:35.440
behind only traces that detectors must somehow reconstruct and disentangle
686
00:54:35.500 --> 00:54:40.239
from background noise. Creating the conditions for their birth and
687
00:54:40.280 --> 00:54:46.750
then catching their death requires extraordinary instrumental precision. The theoretical
688
00:54:46.809 --> 00:54:52.039
community remained interested, developing models and making predictions about what
689
00:54:52.119 --> 00:54:56.059
these exotic states should look like if they existed. But
690
00:54:56.099 --> 00:55:01.809
without experimental evidence, the field remained largely speculative, confined to
691
00:55:01.829 --> 00:55:06.570
the margins of particle physics research where ambitious ideas waited
692
00:55:06.630 --> 00:55:10.750
for technology to catch up. The first credible evidence for
693
00:55:10.829 --> 00:55:16.090
exotic hadrons only began appearing in the early 2000s, and
694
00:55:16.210 --> 00:55:21.150
even then the results were contested. Some signals appeared, then
695
00:55:21.250 --> 00:55:26.110
failed to replicate. The history of exotic hadron searches before
696
00:55:26.150 --> 00:55:30.610
the LHC is largely a history of false starts. Then
697
00:55:30.650 --> 00:55:36.469
the LHCb experiment came online, and the picture changed. LHCb
698
00:55:36.530 --> 00:55:41.579
was designed specifically to study particles containing bottom and charm quarks,
699
00:55:42.079 --> 00:55:45.420
the heavier members of the quark family. It was built
700
00:55:45.460 --> 00:55:49.880
with exceptional precision tracking. because the decays it was chasing
701
00:55:49.980 --> 00:55:54.510
happened close to the collision point and required careful reconstruction
702
00:55:54.550 --> 00:55:59.429
of particle trajectories. That combination of heavy quark production and
703
00:55:59.489 --> 00:56:03.050
precision tracking turned out to be exactly what was needed
704
00:56:03.110 --> 00:56:09.300
to find exotic hadrons. In 2014, LHCb announced the first
705
00:56:09.489 --> 00:56:16.369
unambiguous observation of a tetraquark. Then pentaquarks followed in 2015.
706
00:56:16.369 --> 00:56:22.510
And then the discoveries started accelerating. By 2022, the situation
707
00:56:22.550 --> 00:56:28.590
had become remarkable. In a single announcement, LHCb reported three
708
00:56:28.690 --> 00:56:33.050
new particles at once, a new kind of pentaquark and
709
00:56:33.090 --> 00:56:37.909
the first ever pair of tetraquarks observed together. The pentaquark
710
00:56:37.949 --> 00:56:44.369
was something physicists had not seen before. Designated PLPPSS 4338,
711
00:56:47.670 --> 00:56:50.690
It was the first pentaquark ever found to contain a
712
00:56:50.809 --> 00:56:55.760
strange quark alongside a charm quark and a charm antiquark.
713
00:56:56.340 --> 00:57:01.340
Most previous pentaquarks contained charm quarks but no strange quarks.
714
00:57:02.019 --> 00:57:05.960
This one did both. That combination had been predicted as
715
00:57:06.059 --> 00:57:10.599
theoretically possible, but confirming it required finding it in the data,
716
00:57:11.099 --> 00:57:15.199
separating it from background noise, and verifying that the signal
717
00:57:15.239 --> 00:57:20.349
was real. The statistical significance of that discovery was 15
718
00:57:20.349 --> 00:57:26.170
standard deviations. That number is worth pausing on. In particle physics,
719
00:57:26.710 --> 00:57:31.159
the threshold for claiming a discovery is 5 standard deviations,
720
00:57:31.739 --> 00:57:34.780
a level of confidence that means the probability of a
721
00:57:34.840 --> 00:57:40.500
statistical fluke producing the same result is roughly 1 in 3.5 million.
722
00:57:40.500 --> 00:57:45.449
15 standard deviations is not close to the threshold. It
723
00:57:45.530 --> 00:57:49.610
is three times past it. The strange pentaquark was not
724
00:57:49.670 --> 00:57:53.449
a hint or an anomaly. It was a clean, overwhelming
725
00:57:53.570 --> 00:57:57.139
signal sitting in the detector data like a neon sign.
726
00:57:57.659 --> 00:58:04.320
The two tetraquarks announced at the same time, tax zero, 2,900 zero,
727
00:58:05.000 --> 00:58:09.230
added something different to the picture. The doubly charged version
728
00:58:09.329 --> 00:58:14.449
was notable because its charge was unusual. Standard mesons carry
729
00:58:14.690 --> 00:58:19.170
one unit of charge at most. A tetraquark carrying two
730
00:58:19.329 --> 00:58:23.840
units of positive charge cannot be explained as a quark-antiquark
731
00:58:23.889 --> 00:58:29.059
pair under any interpretation. Its charge alone was proof that
732
00:58:29.099 --> 00:58:33.420
it contained at least four quarks. There was no ambiguity
733
00:58:33.480 --> 00:58:38.719
about its exotic nature. The particle's properties forced that conclusion
734
00:58:38.780 --> 00:58:44.010
before any deeper analysis was needed. What made the 2022
735
00:58:44.010 --> 00:58:49.380
announcements significant beyond the discoveries themselves was what they implied
736
00:58:49.420 --> 00:58:54.260
about the particle zoo now repeating. The LHC, across its
737
00:58:54.360 --> 00:59:00.460
first three runs, found more than 85 new hadrons in total.
738
00:59:00.460 --> 00:59:05.090
23 of them were confirmed exotic states, 5 pentaquarks and
739
00:59:05.090 --> 00:59:09.929
18 tetraquarks, each one containing at least one charm quark.
740
00:59:10.739 --> 00:59:13.860
That number is growing, and the pace has not slowed.
741
00:59:14.659 --> 00:59:19.809
History was not just echoing, it was replaying at higher resolution,
742
00:59:20.070 --> 00:59:25.469
with more sophisticated instruments and more particles than the 1950s
743
00:59:25.570 --> 00:59:29.949
physicists had encountered. The question that follows all of this
744
00:59:30.090 --> 00:59:33.590
is the one that matters most. What is it actually
745
00:59:33.699 --> 00:59:39.320
telling us? Finding new hadrons is interesting. Finding dozens of
746
00:59:39.380 --> 00:59:44.000
exotic hadrons is something else. It means the strong force,
747
00:59:44.380 --> 00:59:50.119
the fundamental interaction that holds quarks together inside protons and neutrons,
748
00:59:50.550 --> 00:59:55.760
is richer and stranger than the standard picture assumed. QCD
749
00:59:55.840 --> 01:00:01.280
permits these exotic combinations in principle, but the theory's predictions
750
01:00:01.360 --> 01:00:05.000
about how they form, how stable they are, and what
751
01:00:05.079 --> 01:00:10.409
internal structure they have are genuinely difficult to calculate. The
752
01:00:10.469 --> 01:00:14.210
strong force does not yield to simple mathematics the way
753
01:00:14.269 --> 01:00:20.019
electromagnetism does. Its equations are notoriously hard to solve at
754
01:00:20.119 --> 01:00:24.539
low energies. which is precisely the energy range where hadrons
755
01:00:24.619 --> 01:00:29.489
form and decay. Each new exotic particle is a test case.
756
01:00:30.199 --> 01:00:35.510
Its mass, its decay products, its lifetime. These are measurements
757
01:00:35.570 --> 01:00:40.449
that can be compared against theoretical predictions. When the predictions match,
758
01:00:41.130 --> 01:00:45.409
QCD gets validated in a new corner of its parameter space.
759
01:00:45.969 --> 01:00:49.699
When they do not match, something in the theoretical framework
760
01:00:49.760 --> 01:00:55.949
needs adjusting. The strange pentaquark, the doubly charged tetraquark, they
761
01:00:55.989 --> 01:00:59.510
are not just entries in a catalogue, they are probes
762
01:00:59.570 --> 01:01:03.300
into how the strong force actually behaves when quarks are
763
01:01:03.340 --> 01:01:08.800
arranged in configurations that protons and neutrons never encounter. Two
764
01:01:08.920 --> 01:01:13.400
charm quarks sitting inside a five quark system create a
765
01:01:13.539 --> 01:01:17.539
very different dynamic than two light quarks in a proton.
766
01:01:18.260 --> 01:01:23.460
The interaction strengths are different. The spatial distributions are different.
767
01:01:24.039 --> 01:01:27.699
The binding mechanisms may be different in ways that current
768
01:01:27.780 --> 01:01:33.969
models handle only approximately. Some theorists believe these exotic hadrons
769
01:01:34.030 --> 01:01:39.150
are genuinely compact objects. Four or five quarks tightly bound
770
01:01:39.210 --> 01:01:43.079
together the way quarks are bound in a proton. Others
771
01:01:43.159 --> 01:01:48.420
believe they are molecular states. Two ordinary hadrons orbiting each
772
01:01:48.480 --> 01:01:53.460
other loosely. held together by residual strong force interactions the
773
01:01:53.519 --> 01:01:59.300
way hydrogen atoms bind into H2 molecules. The distinction matters.
774
01:01:59.949 --> 01:02:06.150
Compact tetraquarks and molecular tetraquarks would test different aspects of QCD.
775
01:02:07.010 --> 01:02:12.550
Figuring out which interpretation is correct requires more data, higher
776
01:02:12.630 --> 01:02:17.420
precision measurements, and theoretical tools that are still being developed.
777
01:02:18.190 --> 01:02:23.070
A problem of this scale naturally mobilizes entire generations of
778
01:02:23.170 --> 01:02:28.110
theorists to work together on the same fundamental questions. The
779
01:02:28.190 --> 01:02:33.130
experimental results are outrunning the theory's ability to fully explain them,
780
01:02:33.690 --> 01:02:38.150
which is exactly the situation that drives physics forward. In
781
01:02:38.190 --> 01:02:43.489
the 1950s, the particle zoo looked like chaos until quarks
782
01:02:43.590 --> 01:02:47.960
gave its structure. Now the zoo has grown again. And
783
01:02:48.000 --> 01:02:51.639
the structure that explains it is not yet fully written.
784
01:02:52.320 --> 01:02:57.289
More than 85 new hadrons discovered across three LHC runs.
785
01:02:58.010 --> 01:03:00.869
And the theory that is supposed to explain all of
786
01:03:00.929 --> 01:03:04.730
them is still catching up. Protons have been around since
787
01:03:04.789 --> 01:03:08.929
the first moments after the Big Bang. Physicists have been
788
01:03:09.010 --> 01:03:13.440
studying them for almost a century. That makes it strange
789
01:03:13.519 --> 01:03:17.630
that a particle four times heavier than a proton made
790
01:03:17.670 --> 01:03:24.030
of a similar arrangement of quarks, went unconfirmed until 2017.
791
01:03:24.030 --> 01:03:28.900
The particle is called the Kexi-CC nums, pronounced roughly as
792
01:03:29.340 --> 01:03:35.119
XICC +. And its discovery by the LHCb experiment at
793
01:03:35.219 --> 01:03:38.800
CERN was not a surprise in the sense that theorists
794
01:03:38.860 --> 01:03:42.949
had been predicting something like it for decades. It was
795
01:03:42.989 --> 01:03:46.170
a surprise in the sense that theorists had been predicting
796
01:03:46.289 --> 01:03:50.190
something like it for decades. It was a surprise in
797
01:03:50.230 --> 01:03:53.869
the sense that theorists had been predicting something like it
798
01:03:54.289 --> 01:03:59.380
for decades. To understand why this particle matters, you need
799
01:03:59.420 --> 01:04:04.119
a picture of what it actually is. A proton contains
800
01:04:04.239 --> 01:04:08.639
three quarks. Two of them are up quarks. One is
801
01:04:08.699 --> 01:04:12.409
a down quark. These are the lightest quarks in existence,
802
01:04:12.849 --> 01:04:17.860
essentially massless by the standards of particle physics. The strong
803
01:04:17.960 --> 01:04:21.739
force holds them together. Because the quarks are so light,
804
01:04:22.199 --> 01:04:25.139
they move at speeds close to the speed of light
805
01:04:25.199 --> 01:04:29.989
inside the proton. The whole system is chaotic. The quarks
806
01:04:30.030 --> 01:04:35.440
themselves contribute almost nothing to the proton's mass. Nearly all
807
01:04:35.480 --> 01:04:38.320
of that mass comes from the energy of the gluons
808
01:04:38.380 --> 01:04:42.559
and the constant motion inside, a fact strange enough to
809
01:04:42.619 --> 01:04:48.380
deserve its own pause. The XKCC nuff has a different structure.
810
01:04:48.900 --> 01:04:53.670
It contains two charm quarks and one down quark. Charm
811
01:04:53.730 --> 01:04:57.909
quarks are heavy. Each one carries roughly 1,200 times the
812
01:04:57.929 --> 01:04:59.769
mass of an up quark. Put two of them in
813
01:04:59.829 --> 01:05:06.150
the same particle, And the result is something with a
814
01:05:06.230 --> 01:05:12.739
total mass around three 620 mega electron volts, about four
815
01:05:12.840 --> 01:05:16.760
times the mass of a proton. The down quark rides
816
01:05:16.840 --> 01:05:22.099
along almost as a passenger, contributing comparatively little to the total.
817
01:05:22.719 --> 01:05:26.739
This is a fundamentally different kind of hadron than anything
818
01:05:26.800 --> 01:05:31.869
in an ordinary nucleus. Here is why physicists care. The
819
01:05:31.949 --> 01:05:36.320
strong force which binds quarks together is described by a
820
01:05:36.440 --> 01:05:40.440
theory called quantum chromodynamics. It is one of the most
821
01:05:40.579 --> 01:05:46.099
precisely tested theories in all of physics. But quantum chromodynamics
822
01:05:46.159 --> 01:05:50.570
has a peculiar property. It behaves very differently depending on
823
01:05:50.610 --> 01:05:54.710
the energy scale at which it is operating. At high energies,
824
01:05:55.130 --> 01:06:01.329
the strong force weakens. Quarks inside high energy collisions barely interact.
825
01:06:02.070 --> 01:06:06.469
At low energies, the force becomes so strong that quarks
826
01:06:06.570 --> 01:06:10.550
cannot be separated at all. Pull two quarks apart and
827
01:06:10.590 --> 01:06:14.389
the energy you spend just creates new quarks rather than
828
01:06:14.550 --> 01:06:20.030
freeing the original ones. This behavior is called confinement. It
829
01:06:20.090 --> 01:06:22.630
is one of the strangest features of nature at the
830
01:06:22.710 --> 01:06:26.949
subatomic level. The problem is that the low energy regime
831
01:06:26.989 --> 01:06:32.570
of quantum chromodynamics The regime where ordinary protons and neutrons
832
01:06:32.670 --> 01:06:39.460
live is extraordinarily difficult to calculate. The mathematics becomes intractable.
833
01:06:40.360 --> 01:06:47.039
Physicists have to use approximation methods, numerical simulations, educated guesses
834
01:06:47.119 --> 01:06:50.630
to work out what the theory actually predicts for bound
835
01:06:50.710 --> 01:06:54.489
states of light quarks. There is a gap between the
836
01:06:54.670 --> 01:06:58.269
elegance of the equations and the ability to solve them
837
01:06:58.349 --> 01:07:03.610
precisely in ordinary matter. This is where the XKCC num
838
01:07:03.670 --> 01:07:07.590
becomes a tool rather than just a curiosity. When both
839
01:07:07.730 --> 01:07:11.320
quarks in a system are heavy, the physics changes in
840
01:07:11.360 --> 01:07:15.579
a useful way. Heavy quarks move slowly relative to the
841
01:07:15.639 --> 01:07:19.780
speed of light, even inside a bound particle. The system
842
01:07:19.820 --> 01:07:23.849
becomes more ordered, more calculable. It is somewhat like the
843
01:07:23.949 --> 01:07:27.670
difference between trying to describe the behavior of a chaotic
844
01:07:27.789 --> 01:07:31.610
gas and describing the motion of two heavy planets in
845
01:07:31.650 --> 01:07:36.449
a gravitational orbit. The heavy system yields to mathematics in
846
01:07:36.510 --> 01:07:40.519
a way the light system does not. Physicists call this
847
01:07:40.579 --> 01:07:44.300
the heavy quark limit. It has been exploited with great
848
01:07:44.360 --> 01:07:48.699
success in systems containing a single charm quark or a
849
01:07:48.820 --> 01:07:54.550
single bottom quark. The CLICCCC nub pushes into territory that
850
01:07:54.590 --> 01:07:59.579
had never been experimentally confirmed before, a system where two
851
01:07:59.699 --> 01:08:05.440
heavy quarks are bound together simultaneously, with the third, lighter
852
01:08:05.519 --> 01:08:09.590
quark orbiting the pair. Theorists have predicted that the two
853
01:08:09.690 --> 01:08:13.690
charm quarks would form a tight inner system, almost like
854
01:08:13.730 --> 01:08:17.489
a tiny nucleus of their own, with the down quarks
855
01:08:17.569 --> 01:08:21.500
circling around them at a much larger distance. The whole
856
01:08:21.619 --> 01:08:26.340
object would resemble in a rough structural sense, a hydrogen atom,
857
01:08:26.840 --> 01:08:30.140
with the charm-charm core playing the role of the nucleus
858
01:08:30.479 --> 01:08:33.359
and the down quark playing the role of the electron.
859
01:08:33.819 --> 01:08:38.500
This analogy has limits, as all analogies in particle physics do,
860
01:08:39.119 --> 01:08:43.979
but the two-layer structure was a genuine theoretical prediction waiting
861
01:08:44.039 --> 01:08:52.590
for experimental verification. When LHCb confirmed the XACC nub in 2017,
862
01:08:52.590 --> 01:08:55.039
It did more than add a name to a list.
863
01:08:55.600 --> 01:08:59.840
It gave theorists an actual measurement to test against. The
864
01:08:59.899 --> 01:09:07.170
mass came in at 3621.4 megalectron volts. That number could
865
01:09:07.210 --> 01:09:12.909
be compared directly to predictions from quantum chromodynamic simulations. The
866
01:09:12.949 --> 01:09:18.590
comparison revealed something important. The theoretical calculations had gotten the
867
01:09:18.670 --> 01:09:24.220
structure roughly right, but the fine details required adjustment. The
868
01:09:24.300 --> 01:09:27.140
measurements placed pressure on the models in a way that
869
01:09:27.279 --> 01:09:32.500
decades of studying ordinary protons simply could not. This was
870
01:09:32.560 --> 01:09:38.439
because ordinary protons are too tangled, too light, too relativistic
871
01:09:38.510 --> 01:09:42.520
to serve as clean tests of the theory's predictions. There
872
01:09:42.579 --> 01:09:45.079
is also the question of what the strong force is
873
01:09:45.300 --> 01:09:49.460
actually doing when it holds two heavy quarks together. In
874
01:09:49.500 --> 01:09:53.819
a proton, the three light quarks are so mobile and
875
01:09:53.840 --> 01:09:58.340
the gluon field so energetic that describing the binding in
876
01:09:58.500 --> 01:10:03.270
simple terms is nearly impossible. In a double charm system,
877
01:10:03.890 --> 01:10:07.109
the binding between the two charm quarks can be studied
878
01:10:07.170 --> 01:10:12.050
more directly. It behaves, in some respects, like a miniaturized
879
01:10:12.119 --> 01:10:17.350
version of the force that holds atomic nuclei together, operating
880
01:10:17.390 --> 01:10:22.409
at a far smaller scale. The similarity is not coincidental.
881
01:10:23.010 --> 01:10:27.109
Both arise from the same underlying theory. But the double
882
01:10:27.189 --> 01:10:31.439
charm system lets physicists study the mechanism with a clarity
883
01:10:31.500 --> 01:10:35.890
that nuclear physics, Operating at larger scales and with more
884
01:10:35.989 --> 01:10:42.710
complicated many-body interactions cannot provide. What makes this particularly striking
885
01:10:42.810 --> 01:10:47.930
is that the XKCC Nung is unstable. Its lifetime is
886
01:10:48.010 --> 01:10:51.939
measured in fractions of a second, so small the number
887
01:10:51.989 --> 01:10:55.300
itself is difficult to write in a way that means
888
01:10:55.399 --> 01:10:59.979
anything to ordinary intuition. It exists long enough to travel
889
01:11:00.020 --> 01:11:04.180
a few millimeters inside a detector. a track that the
890
01:11:04.340 --> 01:11:09.319
LHCb could reconstruct from the particles it decays into. That
891
01:11:09.479 --> 01:11:14.270
brief existence is enough to measure its mass, its decay modes,
892
01:11:15.090 --> 01:11:19.970
the properties of its internal structure. The measurement is precise.
893
01:11:20.630 --> 01:11:26.220
The implications for understanding the strong force are significant. Physicists
894
01:11:26.319 --> 01:11:30.850
expect that the discovery of the X-carc-CC scene is not
895
01:11:30.909 --> 01:11:34.310
the end of this line of investigation, but the beginning.
896
01:11:34.890 --> 01:11:39.590
There are other double heavy particles predicted by quantum chromodynamics,
897
01:11:40.289 --> 01:11:45.750
systems involving bottom quarks, or combinations of charm and bottom
898
01:11:45.810 --> 01:11:49.939
quarks that have not yet been observed. Each one would
899
01:11:50.029 --> 01:11:55.079
probe a slightly different corner of the theory, testing calculations
900
01:11:55.140 --> 01:11:59.199
that cannot be checked any other way. The LHCb was
901
01:11:59.279 --> 01:12:03.260
built with the sensitivity to find these particles if they exist.
902
01:12:04.159 --> 01:12:08.000
The datasets from Run 3 contain collisions that may already
903
01:12:08.100 --> 01:12:12.569
hold the evidence, waiting to be extracted through careful analysis.
904
01:12:13.470 --> 01:12:16.590
Two charm quarks in the same particle turn out to
905
01:12:16.630 --> 01:12:20.510
behave nothing like two light quarks would. That difference is
906
01:12:20.590 --> 01:12:23.810
exactly the kind of thing that forces theorists back to
907
01:12:23.850 --> 01:12:28.229
their equations. For a tiny fraction of a second after
908
01:12:28.270 --> 01:12:31.810
the Big Bang, less than a millionth of a second,
909
01:12:32.449 --> 01:12:36.930
the entire universe existed as a single churning soup of
910
01:12:37.149 --> 01:12:43.260
quarks and gluons, with no protons, no neutrons, no atoms,
911
01:12:43.850 --> 01:12:49.479
nothing organised at all. Every particle that would eventually become stars,
912
01:12:49.640 --> 01:12:54.739
planets and people was dissolved into this primordial broth. moving
913
01:12:54.840 --> 01:12:58.649
too fast and packed too tightly to form anything stable.
914
01:12:59.569 --> 01:13:05.770
Then the universe cooled. Quarks clumped into hadrons. Structure began.
915
01:13:06.449 --> 01:13:11.239
The soup became a world. That transition happened once, nearly
916
01:13:11.239 --> 01:13:15.859
14 billion years ago, and for most of scientific history
917
01:13:15.899 --> 01:13:19.430
there was no way to study it directly. The only
918
01:13:19.520 --> 01:13:24.649
record it left behind was the universe itself. Physicists call
919
01:13:24.720 --> 01:13:30.560
that original state quark-gluon plasma. The name is descriptive. In
920
01:13:30.779 --> 01:13:36.199
ordinary matter, quarks are locked inside protons and neutrons, bound
921
01:13:36.260 --> 01:13:40.439
together so tightly that pulling them apart requires more energy
922
01:13:40.479 --> 01:13:44.319
than it takes to simply create new quarks. They are
923
01:13:44.399 --> 01:13:49.119
never free. But at temperatures and densities high enough, that
924
01:13:49.229 --> 01:13:55.260
confinement breaks down. The boundaries dissolve. Quarks and gluons stop
925
01:13:55.300 --> 01:13:59.199
belonging to any particular particle and become part of a
926
01:13:59.279 --> 01:14:04.979
collective state, a fluid of fundamental constituents with no internal
927
01:14:05.079 --> 01:14:08.949
structure above them. This is what the universe was in
928
01:14:09.010 --> 01:14:14.590
its first microsecond. Not a gas of particles. Not empty
929
01:14:14.710 --> 01:14:21.539
space punctuated by atoms. A single undifferentiated plasma stretching in
930
01:14:21.819 --> 01:14:27.680
every direction. The LHC recreates this state by abandoning protons
931
01:14:27.739 --> 01:14:33.430
entirely and switching to lead ions. A lead nucleus contains
932
01:14:33.430 --> 01:14:40.489
82 protons and 126 neutrons, packed into a sphere roughly
933
01:14:40.489 --> 01:14:45.949
14 femtometers across. When two of these nuclei are accelerated
934
01:14:46.029 --> 01:14:49.210
to nearly the speed of light and aimed directly at
935
01:14:49.270 --> 01:14:53.590
each other, the collision is not a simple impact. It
936
01:14:53.670 --> 01:14:57.029
is more like two dense crowds running through each other
937
01:14:57.109 --> 01:15:01.590
at full speed. The nuclei overlap for an instant so
938
01:15:01.710 --> 01:15:05.939
brief it is measured in yoctoseconds, and in that instant
939
01:15:05.989 --> 01:15:10.140
the energy density at the collision point reaches temperatures around
940
01:15:10.140 --> 01:15:15.260
5 trillion degrees Celsius. For context, the core of the
941
01:15:15.359 --> 01:15:20.409
Sun sits at roughly 15 million degrees, The LHC heavy
942
01:15:20.550 --> 01:15:24.949
ion collisions are more than 300,000 times hotter than that.
943
01:15:25.489 --> 01:15:30.020
At those temperatures, protons and neutrons cannot hold themselves together.
944
01:15:30.380 --> 01:15:36.560
Quarks break free. Quark-gluon plasma forms, lasting for perhaps 10
945
01:15:36.560 --> 01:15:42.930
yoctoseconds before the system cools and hadrons reassemble. The entire
946
01:15:43.010 --> 01:15:46.909
event is over before light can cross a single proton
947
01:15:47.560 --> 01:15:51.000
Physicists had a clear prediction for what this plasma would
948
01:15:51.039 --> 01:15:56.060
look like. The quarks and gluons, freed from confinement, would
949
01:15:56.100 --> 01:16:02.640
behave like a gas, particles moving independently, rarely interacting, spreading
950
01:16:02.760 --> 01:16:06.810
outward in roughly straight lines from the collision point. This
951
01:16:06.850 --> 01:16:11.529
was a reasonable assumption. Plasma states in ordinary matter, like
952
01:16:11.689 --> 01:16:16.010
ionized gas in a star's atmosphere, behave this way. The
953
01:16:16.050 --> 01:16:20.630
particles are free, and free particles tend not to cooperate.
954
01:16:21.350 --> 01:16:25.850
When the R-Reich C collider at Brookhaven National Laboratory first
955
01:16:25.930 --> 01:16:31.520
produced quark-gluon plasma in 2005, and the LHC later studied
956
01:16:31.579 --> 01:16:36.340
it in far greater detail, the results contradicted that picture
957
01:16:36.420 --> 01:16:41.140
almost completely. The plasma was not behaving like a gas.
958
01:16:41.659 --> 01:16:46.500
It was flowing. When the lead nuclei collide off-centre rather
959
01:16:46.539 --> 01:16:50.409
than head-on, The overlap region is not a perfect sphere,
960
01:16:50.729 --> 01:16:55.550
but an almond shape, elongated in one direction. A gas
961
01:16:55.649 --> 01:17:00.920
expanding from that shape would simply spread outward uniformly, erasing
962
01:17:00.960 --> 01:17:06.899
the geometry almost immediately. Instead, the particles emerging from LHC
963
01:17:07.000 --> 01:17:11.920
heavy ion collisions preserved that almond geometry in their outward flow,
964
01:17:12.739 --> 01:17:16.050
more particles coming out along the long axis than the
965
01:17:16.109 --> 01:17:20.300
short one. This is what a liquid does. A liquid
966
01:17:20.359 --> 01:17:26.359
has internal pressure gradients. It flows collectively, with each part
967
01:17:26.399 --> 01:17:29.300
of the fluid responding to what the rest is doing.
968
01:17:30.180 --> 01:17:34.600
The quark-gluon plasma was not a collection of independent particles.
969
01:17:35.399 --> 01:17:39.029
It was a collective fluid, and it remembered its initial
970
01:17:39.109 --> 01:17:44.069
shape as it expanded. The technical term physicists use is
971
01:17:44.130 --> 01:17:48.789
a nearly perfect liquid. The measure of a fluid's resistance
972
01:17:48.829 --> 01:17:54.789
to flow is viscosity. Water has relatively low viscosity. Hummy
973
01:17:54.869 --> 01:17:59.949
has high viscosity. The quark-gluon plasma produced at the LHC
974
01:18:00.050 --> 01:18:04.090
has a viscosity so close to zero that it approaches
975
01:18:04.149 --> 01:18:08.430
the theoretical minimum allowed by quantum mechanics. There is a
976
01:18:08.529 --> 01:18:13.149
lower bound on viscosity set by the uncertainty principle, a
977
01:18:13.289 --> 01:18:18.270
floor below which no fluid can go. The quark-gluon plasma
978
01:18:18.289 --> 01:18:22.390
sits just above that floor, making it the least viscous
979
01:18:22.470 --> 01:18:28.380
fluid ever observed. It flows more freely than superfluid helium.
980
01:18:29.000 --> 01:18:33.300
It flows more freely than anything else scientists have ever measured.
981
01:18:33.840 --> 01:18:39.779
This was not expected. Strongly interacting particles, which quarks and
982
01:18:39.859 --> 01:18:45.600
gluons certainly are, were supposed to produce a messy, high-viscosity medium.
983
01:18:46.060 --> 01:18:52.140
when liberated. Instead, they produce something almost frictionless. The reason
984
01:18:52.189 --> 01:18:55.060
has to do with the coupling between the particles at
985
01:18:55.100 --> 01:19:01.699
those extreme temperatures. Counterintuitively, the strong force that normally confines
986
01:19:01.819 --> 01:19:05.359
quarks does not simply vanish when they are freed. The
987
01:19:05.420 --> 01:19:08.819
quarks remain strongly coupled to each other even in the
988
01:19:08.880 --> 01:19:13.930
plasma phase. just without the confinement that strong coupling is
989
01:19:13.989 --> 01:19:19.590
what produces the collective behavior the plasma flows together because
990
01:19:19.649 --> 01:19:23.520
its constituents are still constantly talking to each other through
991
01:19:23.600 --> 01:19:29.079
blue on exchange reacting and adjusting in concert the fluid
992
01:19:29.159 --> 01:19:35.569
is strongly interacting and strongly interacting fluids can have extraordinarily
993
01:19:35.729 --> 01:19:40.500
low viscosity under the right conditions The ALICE experiment at
994
01:19:40.539 --> 01:19:44.819
the LHC was built specifically to study this state of matter.
995
01:19:45.569 --> 01:19:49.350
It tracked tens of thousands of particles produced in a
996
01:19:49.529 --> 01:19:56.180
single heavy ion collision, measuring their momenta, their angles, their identities.
997
01:19:56.850 --> 01:20:02.239
From those measurements, physicists reconstructed the flow patterns of the plasma,
998
01:20:02.880 --> 01:20:07.649
mapped its collective behavior, and began building a detailed picture
999
01:20:07.710 --> 01:20:10.989
of what the early universe actually looked like in its
1000
01:20:11.069 --> 01:20:15.880
first moments. The data from Run 3 added precision to
1001
01:20:15.939 --> 01:20:21.220
that picture. New measurements of the plasma's expansion velocity, its
1002
01:20:21.319 --> 01:20:25.510
temperature gradients, and its response to the geometry of different
1003
01:20:25.569 --> 01:20:31.229
collisions confirmed and extended what earlier runs had suggested. What
1004
01:20:31.270 --> 01:20:34.930
this tells us about the early universe is both specific
1005
01:20:35.189 --> 01:20:39.289
and unsettling. The standard picture of the Big Bang's first
1006
01:20:39.409 --> 01:20:44.079
microsecond had assumed the universe was a hot, relatively simple
1007
01:20:44.159 --> 01:20:49.399
medium that expanded and cooled until quarks condensed into hadrons.
1008
01:20:50.000 --> 01:20:53.340
The plasma turns out to be far more structured than that.
1009
01:20:53.899 --> 01:20:58.270
It has collective modes. It has flow. It has memory
1010
01:20:58.310 --> 01:21:01.989
of its initial geometry. The early universe was not an
1011
01:21:02.069 --> 01:21:09.819
undifferentiated chaos, but something with internal dynamics, internal correlations, behaving
1012
01:21:09.939 --> 01:21:14.500
more like a coherent fluid than a random explosion. That
1013
01:21:14.600 --> 01:21:19.420
changes how physicists model the transition from plasma to hadrons,
1014
01:21:20.079 --> 01:21:23.300
and it changes what assumptions are safe to make about
1015
01:21:23.399 --> 01:21:29.180
conditions even earlier. In the first instance before quark-luon plasma
1016
01:21:29.220 --> 01:21:34.289
itself formed, the early universe was not a gas, it
1017
01:21:34.329 --> 01:21:37.810
was a liquid, and that single fact has forced a
1018
01:21:37.930 --> 01:21:42.829
rewrite of the first chapter of cosmic history. Every galaxy
1019
01:21:42.890 --> 01:21:48.250
we have ever observed is spinning too fast, not slightly fast,
1020
01:21:49.010 --> 01:21:51.810
not by a margin that could be explained away with
1021
01:21:51.909 --> 01:21:55.699
better measurements or a rounding error in the math. The
1022
01:21:55.800 --> 01:21:59.020
stars at the outer edges of galaxies are moving at
1023
01:21:59.060 --> 01:22:04.869
velocities that should, according to every gravitational calculation based on
1024
01:22:04.989 --> 01:22:09.970
visible matter, fling them out into the void. A spiral
1025
01:22:10.069 --> 01:22:14.699
galaxy rotating at those speeds, held together only by the
1026
01:22:14.800 --> 01:22:19.359
gravity of its visible stars and gas and dust, should
1027
01:22:19.399 --> 01:22:24.319
be tearing itself apart. It is not. None of them are.
1028
01:22:25.029 --> 01:22:29.090
Every galaxy we have pointed a telescope at holds together,
1029
01:22:29.470 --> 01:22:33.109
and the visible matter inside them is nowhere near enough
1030
01:22:33.170 --> 01:22:37.109
to explain why. The first person to take this problem
1031
01:22:37.250 --> 01:22:42.729
seriously was an astronomer named Vera Rubin, working in the 1970s.
1032
01:22:43.430 --> 01:22:48.630
She measured the rotation curves of spiral galaxies, essentially how
1033
01:22:48.789 --> 01:22:53.010
fast stars move at different distances from the galactic centre.
1034
01:22:55.069 --> 01:22:59.170
based on Newtonian gravity and the distribution of visible mass,
1035
01:22:59.390 --> 01:23:04.250
was clear. Stars farther from the centre should orbit more slowly,
1036
01:23:04.710 --> 01:23:07.869
the same way the outer planets of our solar system
1037
01:23:07.970 --> 01:23:11.750
move more slowly than the inner ones. What she found
1038
01:23:11.829 --> 01:23:17.100
instead was flat curves. Stars far from the centre moved
1039
01:23:17.140 --> 01:23:20.979
at nearly the same speed as stars close in. The
1040
01:23:21.079 --> 01:23:25.909
curve did not drop Something was adding mass that nobody
1041
01:23:25.979 --> 01:23:31.079
could see. Rubin's data was careful. Her methods were sound,
1042
01:23:31.479 --> 01:23:35.720
and the conclusion was unavoidable. Either the laws of gravity
1043
01:23:35.779 --> 01:23:39.220
were wrong at galactic scales, or there was a vast
1044
01:23:39.359 --> 01:23:44.090
quantity of invisible matter wrapped around every galaxy in the universe,
1045
01:23:44.470 --> 01:23:49.010
providing the extra gravitational pull needed to keep stars in orbit.
1046
01:23:49.779 --> 01:23:55.100
Physicists eventually settled on the second explanation. The invisible matter
1047
01:23:55.159 --> 01:23:59.239
got a name, dark matter. It does not emit light.
1048
01:23:59.899 --> 01:24:03.439
It does not absorb light. It does not interact with
1049
01:24:03.479 --> 01:24:07.899
the electromagnetic force at all, which is why no telescope
1050
01:24:07.970 --> 01:24:13.270
can detect it directly. Its only confirmed interaction with ordinary
1051
01:24:13.329 --> 01:24:18.000
matter is gravitational, and there is an enormous amount of it.
1052
01:24:18.789 --> 01:24:23.750
Current measurements put dark matter at roughly 27% of the
1053
01:24:23.850 --> 01:24:30.569
total energy content of the universe. Ordinary matter, atoms, stars, gas,
1054
01:24:31.050 --> 01:24:37.109
everything the standard model describes, accounts for about 5%. Dark
1055
01:24:37.210 --> 01:24:40.729
matter outweighs everything we have ever seen or touched by
1056
01:24:40.789 --> 01:24:44.390
more than 5 to 1. The standard model has no
1057
01:24:44.489 --> 01:24:48.850
candidate for it. Not a single particle in the entire
1058
01:24:48.970 --> 01:24:53.369
framework of known physics matches the description. This is not
1059
01:24:53.449 --> 01:24:57.590
a minor gap in an otherwise complete theory. The most
1060
01:24:57.670 --> 01:25:01.670
successful theory in the history of science says nothing about
1061
01:25:01.710 --> 01:25:05.960
the dominant form of matter in the universe. Physicists have
1062
01:25:06.020 --> 01:25:11.239
spent decades proposing candidates. The most popular class for many
1063
01:25:11.300 --> 01:25:17.189
years was called WIMPs, Weakly Interacting Massive Particles. The idea
1064
01:25:17.250 --> 01:25:20.750
was that dark matter consists of particles with masses in
1065
01:25:20.789 --> 01:25:24.010
the range of a few GeV to a few TeV,
1066
01:25:24.569 --> 01:25:29.350
interacting through the weak nuclear force. WIMPs were attractive because
1067
01:25:29.409 --> 01:25:33.220
they arose naturally in certain extensions of the Standard Model,
1068
01:25:33.720 --> 01:25:38.640
particularly supersymmetry, and because the predicted relic abundance from the
1069
01:25:38.739 --> 01:25:44.020
early universe matched the observed dark matter density. This coincidence
1070
01:25:44.060 --> 01:25:48.760
had a name, the WIMP miracle. The Large Hadron Collider
1071
01:25:48.800 --> 01:25:53.020
was well positioned to find WIMPs, if they existed. At
1072
01:25:53.090 --> 01:25:57.329
the energies the LHC reaches, the weak force operates at
1073
01:25:57.449 --> 01:26:01.630
full strength, and WIMPs, if they are real, should be
1074
01:26:01.689 --> 01:26:08.729
producible in proton-proton collisions. The experimental signature is distinctive. A
1075
01:26:08.810 --> 01:26:14.189
WIMP would escape the detector entirely, carrying energy away invisibly.
1076
01:26:15.029 --> 01:26:19.010
But the total energy going into a collision is known precisely,
1077
01:26:19.590 --> 01:26:22.340
so a wimp leaving the detector would show up as
1078
01:26:22.399 --> 01:26:26.239
a mismatch, energy going in that does not come out
1079
01:26:26.279 --> 01:26:31.960
the other side. Physicists call this missing transverse energy, and
1080
01:26:32.000 --> 01:26:34.819
it is one of the cleanest signals in the business.
1081
01:26:35.939 --> 01:26:40.380
Atlas and CMS spent years hunting for it. Run 1
1082
01:26:40.380 --> 01:26:45.199
found nothing. Run 2 found nothing. Run 3 pushed the
1083
01:26:45.260 --> 01:26:50.090
search deeper, with higher collision energies and better detector resolution,
1084
01:26:50.659 --> 01:26:54.710
and the answer was the same. No WIMPs appeared. The
1085
01:26:54.750 --> 01:26:58.770
WIMP miracle is looking less miraculous with each passing year.
1086
01:26:59.430 --> 01:27:03.449
This does not mean dark matter does not exist. It
1087
01:27:03.510 --> 01:27:07.279
means WIMPs of the type that the Standard Model's extensions
1088
01:27:07.359 --> 01:27:12.689
predicted most confidently are probably not the answer. And ruling
1089
01:27:12.729 --> 01:27:18.479
that out, while frustrating, is genuinely useful. Every dead end
1090
01:27:18.560 --> 01:27:22.539
in physics narrows the map. The territory that remains is
1091
01:27:22.640 --> 01:27:25.899
still large, but it is smaller than it was before
1092
01:27:25.939 --> 01:27:30.850
the LHC ran its first collision. CERN researchers shifted focus
1093
01:27:30.869 --> 01:27:35.989
toward lighter candidates. The MeV to GV range of dark matter,
1094
01:27:36.510 --> 01:27:40.550
sometimes called light dark matter, offers a different set of
1095
01:27:40.630 --> 01:27:45.560
signatures and a different set of production mechanisms. In this picture,
1096
01:27:46.079 --> 01:27:49.939
dark matter particles are too light to produce missing energy
1097
01:27:50.020 --> 01:27:53.800
signals at the LHC in the conventional sense, but they
1098
01:27:53.880 --> 01:27:57.340
might still be produced if there are mediator particles that
1099
01:27:57.420 --> 01:28:02.520
bridge the dark sector and the visible sector. These mediators
1100
01:28:02.579 --> 01:28:07.699
would be particles carrying force between ordinary matter and dark matter,
1101
01:28:08.319 --> 01:28:12.220
detectable through their decay products even if the dark matter
1102
01:28:12.260 --> 01:28:18.460
itself escapes. The LHCb experiment, with its forward geometry and
1103
01:28:18.579 --> 01:28:25.199
sensitivity to lower mass particles, became particularly useful here. Searches
1104
01:28:25.260 --> 01:28:31.619
for dark photons, hypothetical mediators that mix weakly with ordinary photons,
1105
01:28:32.069 --> 01:28:38.189
were conducted across multiple run periods. Again, nothing definitive appeared.
1106
01:28:38.890 --> 01:28:40.590
The hunt also turned out to be a success. toward
1107
01:28:40.689 --> 01:28:45.029
particles that barely interact at all with ordinary matter, but
1108
01:28:45.069 --> 01:28:49.069
could be produced in the enormous flux of particles generated
1109
01:28:49.140 --> 01:28:54.300
by the LHC's beams. Some theories predict that dark matter
1110
01:28:54.380 --> 01:28:59.569
annihilates into standard model particles through new forces, at rates
1111
01:28:59.630 --> 01:29:03.229
that depend on the collision energy in ways that accelerator
1112
01:29:03.289 --> 01:29:08.430
experiments can probe directly. The advantage of this approach is
1113
01:29:08.470 --> 01:29:11.729
that it does not depend heavily on assumptions about dark
1114
01:29:11.810 --> 01:29:16.340
matter's specific nature. If the dark sector connects to the
1115
01:29:16.399 --> 01:29:20.859
visible sector through any new force, the LHC should see
1116
01:29:20.960 --> 01:29:24.119
some trace of that connection in the decay products of
1117
01:29:24.180 --> 01:29:28.890
the mediators. No such trace has emerged cleanly enough to
1118
01:29:28.970 --> 01:29:33.489
cross the threshold of a confirmed detection. What CERN has
1119
01:29:33.569 --> 01:29:38.270
produced is an extraordinarily detailed map of what dark matter
1120
01:29:38.350 --> 01:29:44.670
is probably not. Supersymmetric partners of standard model particles, once
1121
01:29:44.770 --> 01:29:49.210
the leading theoretical candidates, have been pushed to masses so
1122
01:29:49.310 --> 01:29:53.310
high that they would require energies beyond the LHC's reach
1123
01:29:53.369 --> 01:29:59.369
to produce, Certain classes of extradimensional theories predicted dark matter
1124
01:29:59.409 --> 01:30:05.989
candidates at accessible mass ranges. Those ranges are now ruled out. Axions,
1125
01:30:06.390 --> 01:30:09.930
a class of light particles originally proposed to solve a
1126
01:30:10.069 --> 01:30:14.649
different problem in particle physics, but later recognized as viable
1127
01:30:14.729 --> 01:30:20.670
dark matter candidates, fall outside the LHC's primary detection sensitivity
1128
01:30:21.130 --> 01:30:26.579
and require dedicated experiments to search for. Each exclusion result
1129
01:30:26.640 --> 01:30:32.569
from the LHC's three runs represents real scientific progress, even
1130
01:30:32.630 --> 01:30:37.869
when it delivers no discovery. The honest position, after more
1131
01:30:37.909 --> 01:30:41.789
than a decade of searching with the most powerful collider
1132
01:30:42.010 --> 01:30:46.710
ever operated, is this. The evidence for dark matter from
1133
01:30:46.869 --> 01:30:53.529
astrophysical observations is overwhelming. Gravitational lensing maps of galaxy clusters
1134
01:30:53.649 --> 01:30:58.020
show it bending light in regions containing no visible matter.
1135
01:30:58.600 --> 01:31:03.239
The large-scale structure of the universe, the way galaxies cluster
1136
01:31:03.279 --> 01:31:07.670
into filaments and voids over billions of light years, cannot
1137
01:31:07.710 --> 01:31:13.390
be reproduced in simulations without it. The cosmic microwave background,
1138
01:31:13.810 --> 01:31:17.529
the oldest light in the universe, carries an imprint of
1139
01:31:17.609 --> 01:31:22.460
dark matter's influence from less than 400,000 years after the
1140
01:31:22.500 --> 01:31:27.399
Big Bang. Something is there. The LHC has narrowed the
1141
01:31:27.479 --> 01:31:33.409
search considerably, ruling out large swaths of parameter space. But
1142
01:31:33.470 --> 01:31:36.869
whatever dark matter is, it has not yet shown its
1143
01:31:36.949 --> 01:31:43.210
face inside a detector. In 2025, The Breakthrough Prize Foundation
1144
01:31:43.289 --> 01:31:47.630
gave its top award in fundamental physics to four experiments
1145
01:31:47.729 --> 01:31:51.210
at CERN. Not because they had finished the job, but
1146
01:31:51.270 --> 01:31:54.109
because of how much they had found while doing it.
1147
01:31:54.649 --> 01:32:01.979
The prize went to ATLAS, CMS, ALIS and LHCb. Four collaborations.
1148
01:32:02.819 --> 01:32:08.079
Thousands of physicists spread across dozens of countries. Each experiment
1149
01:32:08.159 --> 01:32:11.970
built around a different set of questions. Each one aimed
1150
01:32:12.050 --> 01:32:15.210
at a different corner of what the standard model either
1151
01:32:15.250 --> 01:32:20.760
predicts or fails to predict. The Breakthrough Prize Foundation cited
1152
01:32:20.880 --> 01:32:26.800
precision measurements of the Higgs boson, probes of rare particle interactions,
1153
01:32:27.539 --> 01:32:31.529
studies of exotic states of matter, and the discovery of
1154
01:32:31.609 --> 01:32:37.350
more than 72 new hadrons. They also cited something less obvious.
1155
01:32:38.029 --> 01:32:43.970
The careful, painstaking measurement of subtle differences between matter and antimatter.
1156
01:32:44.670 --> 01:32:48.140
That last item is not a solved problem. It is
1157
01:32:48.199 --> 01:32:52.159
an open wound in the theory, and the prize recognised
1158
01:32:52.220 --> 01:32:56.060
the people holding it open. Atlas and CMS are the
1159
01:32:56.159 --> 01:33:00.670
two general purpose detectors, each the size of a cathedral,
1160
01:33:01.210 --> 01:33:04.510
each built to catch the debris of proton collisions at
1161
01:33:04.670 --> 01:33:09.810
energies no previous machine could reach. ATLAS confirmed the Higgs
1162
01:33:09.850 --> 01:33:15.399
boson independently of CMS in 2012, and in the years since,
1163
01:33:15.920 --> 01:33:21.119
both experiments have pushed deeper into the Higgs' properties, measuring
1164
01:33:21.220 --> 01:33:25.260
how it decays, how often it decays, and whether those
1165
01:33:25.399 --> 01:33:29.939
numbers match what the equations predict. Some of them do.
1166
01:33:30.779 --> 01:33:34.340
Some of them sit in uncomfortable places just slightly off
1167
01:33:34.420 --> 01:33:37.560
from where the theory puts them. not far enough to
1168
01:33:37.619 --> 01:33:42.859
claim a discovery, far enough to keep theorists awake. ALICE
1169
01:33:42.939 --> 01:33:47.100
is different. It is built not for proton collisions, but
1170
01:33:47.159 --> 01:33:52.189
for heavy ion collisions. Lead smashed into lead at near
1171
01:33:52.250 --> 01:33:58.210
light speed, briefly recreating the quark-gluon plasma of the early universe.
1172
01:33:58.890 --> 01:34:02.760
What ALICE has contributed to the prize is a portrait
1173
01:34:02.819 --> 01:34:06.100
of matter in a state that has not existed since
1174
01:34:06.159 --> 01:34:11.090
the first microseconds after the Big Bang. That portrait turned
1175
01:34:11.170 --> 01:34:15.510
out to be stranger than expected. The plasma behaves like
1176
01:34:15.569 --> 01:34:20.890
a liquid, not a gas. It flows. It has viscosity.
1177
01:34:21.529 --> 01:34:26.479
It is, by certain measures, the most perfect liquid ever observed.
1178
01:34:27.189 --> 01:34:31.510
That finding does not fit comfortably into the picture physicists
1179
01:34:31.550 --> 01:34:36.909
had before the LHC switched on. LHCb sits downstream from
1180
01:34:36.949 --> 01:34:41.479
the main collision point and catches particles that fly forward
1181
01:34:41.520 --> 01:34:46.279
at low angles, specifically the B mesons and baryons that
1182
01:34:46.340 --> 01:34:51.119
carry the signatures of rare decays. It was LHCb that
1183
01:34:51.199 --> 01:34:55.680
built the most precise map of CP violation in baryons.
1184
01:34:56.350 --> 01:35:00.710
It was LHCb that measured the penguin decays that disagreed
1185
01:35:00.770 --> 01:35:05.390
with standard model predictions. It was LHCb that found the
1186
01:35:05.489 --> 01:35:11.270
strange pentaquark, the doubly charged tetraquark, and dozens of other
1187
01:35:11.350 --> 01:35:16.869
exotic states. When the prize committee wrote about subtle differences
1188
01:35:16.970 --> 01:35:21.789
between matter and antimatter, they were writing largely about work
1189
01:35:21.829 --> 01:35:25.890
done inside that detector. But here is the thing about
1190
01:35:25.930 --> 01:35:30.829
the prize that the headlines mostly missed. The breakthrough prize
1191
01:35:30.909 --> 01:35:36.069
in fundamental physics is awarded for achievement. The citation lists
1192
01:35:36.170 --> 01:35:40.789
discoveries and measurements and confirmations. What it does not say
1193
01:35:40.890 --> 01:35:45.149
out loud, but what sits underneath the whole list, is
1194
01:35:45.189 --> 01:35:49.210
that the most important thing these four experiments produced was
1195
01:35:49.329 --> 01:35:53.930
not certainty. It was precision in the face of uncertainty.
1196
01:35:54.439 --> 01:35:57.840
The measurements that matter most right now are the ones
1197
01:35:57.899 --> 01:36:01.760
that almost fit the theory. The decay rates that are
1198
01:36:01.840 --> 01:36:07.279
slightly off, the asymmetries that are larger than expected or smaller,
1199
01:36:07.939 --> 01:36:10.970
the signals that are clean enough to be real and
1200
01:36:11.029 --> 01:36:14.829
not quite large enough to be declared. This is where
1201
01:36:14.869 --> 01:36:20.850
the concept of statistical significance becomes important. In particle physics,
1202
01:36:21.409 --> 01:36:25.630
A result is not a discovery until it reaches 5 sigma.
1203
01:36:26.350 --> 01:36:30.050
Sigma is a measure of standard deviation, a way of
1204
01:36:30.109 --> 01:36:34.449
expressing how far a result sits from what random chance
1205
01:36:34.529 --> 01:36:39.199
would produce. 1 sigma means the result could easily be noise.
1206
01:36:39.199 --> 01:36:44.100
3 sigma gets people interested. 5 sigma means there is
1207
01:36:44.239 --> 01:36:49.520
roughly a 1 in 3.5 million chance that random fluctuation
1208
01:36:49.600 --> 01:36:54.020
produced what you measured. That is the threshold. Below it,
1209
01:36:54.159 --> 01:36:57.939
you report a hint. Above it, you call a press conference.
1210
01:36:58.720 --> 01:37:03.069
Several of the results that contributed to the 2025 Breakthrough
1211
01:37:03.149 --> 01:37:06.489
Prize were sitting at three sigma, three and a half,
1212
01:37:06.890 --> 01:37:14.569
occasionally brushing four. The penguin decay anomalies. Certain Higgs coupling measurements.
1213
01:37:15.350 --> 01:37:21.399
Some of the matter-antimatter asymmetry numbers. Not quite five. Not
1214
01:37:21.550 --> 01:37:25.770
quite a discovery, but not going away either. This is
1215
01:37:25.829 --> 01:37:29.470
a specific kind of scientific situation that does not map
1216
01:37:29.609 --> 01:37:34.029
cleanly onto the way science is usually explained. The textbook
1217
01:37:34.090 --> 01:37:38.109
version of physics says, you measure something, you compare it
1218
01:37:38.149 --> 01:37:41.649
to the prediction. If it matches, the theory is confirmed.
1219
01:37:42.029 --> 01:37:46.050
If it does not, the theory needs revision. The reality
1220
01:37:46.109 --> 01:37:50.840
at the LHC is stranger. You measure something with extraordinary precision.
1221
01:37:51.279 --> 01:37:54.319
The number you get is close to what the theory predicts,
1222
01:37:54.859 --> 01:37:58.550
but it is not exactly the same. And the question
1223
01:37:58.689 --> 01:38:01.649
is whether that gap is the beginning of something new,
1224
01:38:02.250 --> 01:38:05.750
or simply the tail of a distribution that will shrink
1225
01:38:05.850 --> 01:38:10.060
back towards the prediction when you collect more data. That
1226
01:38:10.199 --> 01:38:14.140
ambiguity is not a failure of the experiments. It is
1227
01:38:14.180 --> 01:38:17.340
the result of pushing precision to a level that was
1228
01:38:17.520 --> 01:38:21.880
not possible before. Twenty years ago, you could not measure
1229
01:38:21.960 --> 01:38:25.939
a B meson decay rate with enough accuracy to notice
1230
01:38:26.000 --> 01:38:30.340
a 2% discrepancy with the standard model. Now you can.
1231
01:38:30.359 --> 01:38:35.640
The discrepancy might dissolve, it might grow. The prize was
1232
01:38:35.699 --> 01:38:40.449
given partly because these four experiments built machines and methods
1233
01:38:41.050 --> 01:38:45.329
sensitive enough to find a 2% discrepancy in the first place.
1234
01:38:46.090 --> 01:38:51.060
That sensitivity is itself an achievement. independent of what it
1235
01:38:51.140 --> 01:38:56.479
eventually reveals. The most significant scientific results do not always
1236
01:38:56.560 --> 01:39:01.590
come with clean answers attached. Sometimes a result matters because
1237
01:39:01.649 --> 01:39:07.029
of the question it refuses to close. The 2025 Breakthrough
1238
01:39:07.130 --> 01:39:11.069
Prize was awarded to four experiments that have spent over
1239
01:39:11.109 --> 01:39:17.050
a decade generating exactly those results, precise enough to be meaningful.
1240
01:39:17.640 --> 01:39:21.430
unresolved enough to demand more work, that is not a
1241
01:39:21.479 --> 01:39:25.810
consolation prize for not finishing. That is a recognition that
1242
01:39:25.850 --> 01:39:29.350
the most valuable thing you can do in science sometimes
1243
01:39:29.430 --> 01:39:31.909
is to find the edge of what the theory can
1244
01:39:31.989 --> 01:39:36.689
explain and hold it there, clearly, until the next generation
1245
01:39:36.729 --> 01:39:41.329
of machines can push further. Five sigma is the threshold
1246
01:39:41.390 --> 01:39:45.460
for a discovery. and several of the most interesting results
1247
01:39:45.520 --> 01:39:48.960
from Run 3 are sitting just below it, which is
1248
01:39:49.060 --> 01:39:53.399
either a sign of statistical moiz, or the most frustrating
1249
01:39:53.479 --> 01:39:56.840
position in the history of physics to be in. The
1250
01:39:56.920 --> 01:40:03.810
number 125.4 inverse femtobarns sounds like nothing until you work
1251
01:40:03.890 --> 01:40:08.350
out what it represents in actual particle collisions. An inverse
1252
01:40:08.430 --> 01:40:12.649
femtobarn is a unit of measurement for collision beta, a
1253
01:40:12.710 --> 01:40:16.560
way of counting how many opportunities existed for a rare
1254
01:40:16.640 --> 01:40:22.079
event to occur inside a detector. One inverse femtobarn corresponds
1255
01:40:22.140 --> 01:40:28.399
to roughly 70 trillion proton-proton collisions. Multiply that by 125.4
1256
01:40:28.399 --> 01:40:34.239
and you are looking at something close to 9 quadrillion
1257
01:40:34.350 --> 01:40:39.739
collision events recorded across RUM3 alone. That is more data
1258
01:40:39.760 --> 01:40:43.659
than the LHC had delivered in any previous single year
1259
01:40:43.720 --> 01:40:48.020
of operation. It is a number that stops making intuitive
1260
01:40:48.100 --> 01:40:52.750
sense almost immediately, which is part of why physicists use
1261
01:40:52.789 --> 01:40:58.789
the shorthand. The collisions themselves happen fast. At full luminosity,
1262
01:40:58.869 --> 01:41:04.800
the LHC produces around 600 million proton-proton collisions every second
1263
01:41:05.319 --> 01:41:10.039
inside the main detectors. Most of those collisions are not interesting.
1264
01:41:10.619 --> 01:41:14.680
Two protons glance off each other, scatter in ordinary ways,
1265
01:41:15.239 --> 01:41:18.859
and produce nothing that wasn't already predicted by the standard
1266
01:41:18.939 --> 01:41:22.760
model before the machine ever switched on. The detectors are
1267
01:41:22.859 --> 01:41:26.819
not recording all of it. They cannot. The data would
1268
01:41:27.090 --> 01:41:32.729
overwhelm every storage system on Earth within minutes. Instead, the
1269
01:41:32.810 --> 01:41:38.659
experiments run trigger systems. layers of fast electronics and algorithms
1270
01:41:39.039 --> 01:41:43.829
that evaluate each collision in microseconds and decide whether it
1271
01:41:43.909 --> 01:41:48.350
is worth keeping. Only about one collision in a million
1272
01:41:48.710 --> 01:41:52.850
passes these filters and gets written to disk. That is
1273
01:41:53.029 --> 01:41:58.130
still an enormous archive, but it means the truly rare events,
1274
01:41:58.729 --> 01:42:02.850
the ones that don't match expectations, have to survive a
1275
01:42:03.029 --> 01:42:08.050
gauntlet of selection before a physicist ever sees them. What
1276
01:42:08.130 --> 01:42:15.810
makes 125.4 inverse femto-barns significant is not just the raw volume,
1277
01:42:16.590 --> 01:42:21.770
it is what that volume unlocks statistically. Rare processes are
1278
01:42:21.869 --> 01:42:26.520
governed by probability. A decay that happens once in every
1279
01:42:26.720 --> 01:42:31.680
billion collisions requires a billion collisions before you can expect
1280
01:42:31.739 --> 01:42:36.270
to see it even once. To study it with any precision,
1281
01:42:36.979 --> 01:42:41.979
to measure its properties, to compare the rate against theoretical predictions,
1282
01:42:42.500 --> 01:42:46.119
to ask whether the numbers agree, you need to see
1283
01:42:46.159 --> 01:42:51.020
it hundreds of times. Run-3 pushed several of the rarest
1284
01:42:51.119 --> 01:42:55.439
processes in particle physics from the category of barely observed
1285
01:42:55.960 --> 01:43:02.460
into the category of measurable. That distinction matters enormously. Observation
1286
01:43:02.539 --> 01:43:06.779
tells you something exists. Measurement tells you how it behaves.
1287
01:43:07.390 --> 01:43:12.289
The measurement of electroweak penguin decays is one example. By
1288
01:43:12.329 --> 01:43:17.470
the end of Run 2, researchers had collected around 650
1289
01:43:17.470 --> 01:43:22.319
billion B meson decays to work with. Run 3 tripled
1290
01:43:22.380 --> 01:43:26.539
that sample. The additional data did not just improve the
1291
01:43:26.579 --> 01:43:31.899
statistics on existing results. It allowed physicists to test new
1292
01:43:32.119 --> 01:43:37.770
angular distributions. new decay products, new corners of the parameter
1293
01:43:37.789 --> 01:43:42.090
space where the standard model makes precise predictions and where
1294
01:43:42.229 --> 01:43:46.340
any unknown particle or force would leave a distinct fingerprint.
1295
01:43:47.270 --> 01:43:50.760
The discrepancies that had been hovering around 3 and 4
1296
01:43:50.760 --> 01:43:55.380
sigma at the end of RUM2, suggestive but not conclusive,
1297
01:43:55.840 --> 01:43:59.960
got sharper. Whether they cross the discovery threshold is a
1298
01:44:00.020 --> 01:44:04.649
question the collaboration is still working through. The people doing
1299
01:44:04.689 --> 01:44:11.949
that work number in the thousands, the four main LHC experiments, ATLAS, CMS,
1300
01:44:12.270 --> 01:44:19.319
ALIS and LHCb, collectively involve more than 10,000 scientists, engineers
1301
01:44:19.399 --> 01:44:24.539
and students drawn from over 100 countries. A single physics
1302
01:44:24.619 --> 01:44:29.590
paper from the ATLAS collaboration can carry more than 3,000 authors.
1303
01:44:30.470 --> 01:44:34.630
That is not a vanity exercise. Every one of those
1304
01:44:34.729 --> 01:44:42.180
people contributed something. Detector calibration, software development, data quality checks,
1305
01:44:42.489 --> 01:44:49.119
statistical analysis, theoretical cross-checks, without which the result would not exist.
1306
01:44:49.880 --> 01:44:52.779
The science at CERN is not done by a genius
1307
01:44:52.880 --> 01:44:56.920
alone in a room. It is done by a civilization-scale
1308
01:44:57.000 --> 01:45:03.260
collaboration running on shared infrastructure and decades of accumulated expertise.
1309
01:45:03.939 --> 01:45:09.760
The organizational structure reflects this complexity. Different physicists focus on
1310
01:45:09.840 --> 01:45:14.899
different aspects. Some optimize the trigger algorithms that separate signal
1311
01:45:14.970 --> 01:45:20.810
from noise. Others concentrate on detector calibration. Still others develop
1312
01:45:20.850 --> 01:45:25.409
the pattern recognition software that reconstructs what happened from raw
1313
01:45:25.449 --> 01:45:32.520
detector signals. There is no single analysis strategy imposed from above. Instead,
1314
01:45:33.220 --> 01:45:38.119
Teams form around physics questions and compete within bounds of courtesy.
1315
01:45:39.039 --> 01:45:43.960
The collaboration moves forward through reasoned debate and accumulated evidence.
1316
01:45:44.939 --> 01:45:49.289
This culture of healthy skepticism embedded in the peer review
1317
01:45:49.369 --> 01:45:55.470
process prevents errors from hardening into published facts. The timeline
1318
01:45:55.510 --> 01:45:59.449
between data collection and published result is longer than most
1319
01:45:59.510 --> 01:46:05.220
people expect A collision event recorded in 2023 might not
1320
01:46:05.300 --> 01:46:11.600
appear in a peer-reviewed paper until 2026 or 2027. The
1321
01:46:11.659 --> 01:46:16.750
raw data has to be reconstructed, translated from detector signals
1322
01:46:16.829 --> 01:46:22.789
into physical quantities like particle momenta and energies. That reconstruction
1323
01:46:22.850 --> 01:46:28.520
requires calibrations that themselves take months to finalize. Once the
1324
01:46:28.569 --> 01:46:34.859
reconstructed data is available, Analysts apply their selection criteria, run
1325
01:46:34.899 --> 01:46:40.449
their statistical models, cross-check against simulation, and then submit to
1326
01:46:40.489 --> 01:46:45.949
the collaboration's internal review process before anything goes public. For
1327
01:46:46.010 --> 01:46:50.289
results touching on possible new physics, the internal review is
1328
01:46:50.390 --> 01:46:55.550
particularly slow and rigorous. Nobody at CERN wants to announce
1329
01:46:55.609 --> 01:47:01.590
a discovery that evaporates under scrutiny. Run-3 confirmed things that
1330
01:47:01.710 --> 01:47:07.250
Run-1 and Run-2 had only sketched. The CP violation signal
1331
01:47:07.329 --> 01:47:11.609
in baryons, the asymmetry between matter and antimatter in the
1332
01:47:11.689 --> 01:47:16.310
particles that make up atomic nuclei, came through with enough
1333
01:47:16.329 --> 01:47:20.529
statistical weight in the combined dataset to move from evidence
1334
01:47:20.590 --> 01:47:27.960
to observation. The exotic Hadron catalogue grew substantially. Several tetraquark
1335
01:47:28.020 --> 01:47:32.229
and pentaquark states that had been seen at marginal significance
1336
01:47:32.279 --> 01:47:36.550
in earlier runs were confirmed at well above the 5-sigma
1337
01:47:36.590 --> 01:47:42.270
threshold using the larger Run-3 sample. The properties of quark-gluon
1338
01:47:42.329 --> 01:47:46.270
plasma were measured with a precision that earlier lead-iron runs
1339
01:47:46.369 --> 01:47:51.220
could not reach. These are not incremental improvements. They represent
1340
01:47:51.260 --> 01:47:56.100
the difference between knowing something exists and understanding how it behaves.
1341
01:47:56.909 --> 01:48:01.319
Higgs boson measurements also advanced. The rare decay of the
1342
01:48:01.380 --> 01:48:06.000
Higgs into two muons, one in every 5,000 Higgs decays,
1343
01:48:06.500 --> 01:48:09.380
had been seen at the edge of observability at the
1344
01:48:09.460 --> 01:48:13.159
end of Run 2. Run 3 moved that result into
1345
01:48:13.329 --> 01:48:17.430
firmer territory, providing the clearest look yet at how the
1346
01:48:17.470 --> 01:48:23.560
Higgs field couples to second-generation fermions. If that coupling deviates
1347
01:48:23.619 --> 01:48:27.479
from the standard model's prediction, the deviation will show up
1348
01:48:27.539 --> 01:48:31.319
in exactly this channel. The data from Run 3 is
1349
01:48:31.460 --> 01:48:35.359
still being analyzed. The final word on whether those muon
1350
01:48:35.439 --> 01:48:39.760
couplings agree with theory has not been written yet. That
1351
01:48:39.840 --> 01:48:43.659
is the situation right now. The machine has gone quiet.
1352
01:48:44.180 --> 01:48:48.600
The tunnels beneath the Swiss-French border are lit by construction equipment,
1353
01:48:49.180 --> 01:48:53.619
not by proton beams. The detectors are being modified. But
1354
01:48:53.659 --> 01:48:59.810
the data that RUN3 produced, nine quadrillion collision events, filtered
1355
01:48:59.869 --> 01:49:04.310
down to the events worth keeping, stored on servers distributed
1356
01:49:04.369 --> 01:49:09.850
across member institutions on multiple continents, That archive is still
1357
01:49:09.890 --> 01:49:14.449
being worked through. Physicists are running analyses that will take
1358
01:49:14.600 --> 01:49:18.979
years to complete. Some results from Run 3 will not
1359
01:49:19.020 --> 01:49:23.779
be published until the High Luminosity LHC is already collecting
1360
01:49:23.840 --> 01:49:29.100
its first new collisions. The gap between data and understanding
1361
01:49:29.180 --> 01:49:32.359
is part of how this science works, and it is
1362
01:49:32.500 --> 01:49:36.000
not a flaw. It is what rigor looks like at
1363
01:49:36.060 --> 01:49:40.600
this scale. The last proton has already circled the ring.
1364
01:49:41.229 --> 01:49:43.529
Now it is up to the data to finish what
1365
01:49:43.569 --> 01:49:48.810
the machine started. Right now, several hundred meters beneath the
1366
01:49:48.890 --> 01:49:54.310
Swiss-French border, workers are dismantling sections of the most complex
1367
01:49:54.409 --> 01:49:58.920
machine ever built by human hands. The tunnel is cold
1368
01:49:58.979 --> 01:50:03.720
and narrow. The equipment inside it cost decades and billions
1369
01:50:03.760 --> 01:50:07.060
of dollars to build. and they are taking it apart
1370
01:50:07.159 --> 01:50:11.819
on purpose. This is Long Shutdown 3, and it is
1371
01:50:12.020 --> 01:50:17.159
not a pause. It is a transformation. The Large Hadron
1372
01:50:17.220 --> 01:50:22.079
Collider that discovered the Higgs Boson, that found more than
1373
01:50:22.079 --> 01:50:27.899
85 new hadrons, that confirmed matter-antimatter asymmetry in the building
1374
01:50:27.939 --> 01:50:32.100
blocks of atomic nuclei, that machine is being replaced by
1375
01:50:32.159 --> 01:50:37.050
something significantly more powerful. The upgrade has a name, the
1376
01:50:37.109 --> 01:50:43.229
High Luminosity LHC or HL-LHC. It is scheduled to begin
1377
01:50:43.310 --> 01:50:47.909
colliding protons again around 2030. What it will do when
1378
01:50:47.970 --> 01:50:51.090
it switches back on is, in the language of physics,
1379
01:50:51.729 --> 01:50:56.079
almost hard to describe without reaching for numbers that sound invented.
1380
01:50:56.659 --> 01:51:01.890
The key word is luminosity. In particle physics, Luminosity is
1381
01:51:01.970 --> 01:51:05.140
a measure of how many collisions a machine can produce
1382
01:51:05.220 --> 01:51:10.880
per second. More luminosity means more events, more data, more
1383
01:51:10.960 --> 01:51:15.319
chances to catch something rare happening in real time. The
1384
01:51:15.399 --> 01:51:21.680
original LHC was already extraordinary in this regard. The HL-LHC
1385
01:51:21.739 --> 01:51:25.199
will deliver roughly 10 times the collision rate of the
1386
01:51:25.260 --> 01:51:30.840
machine that ran through 2026 per year. it will accumulate
1387
01:51:30.880 --> 01:51:35.960
approximately seven times more data than the accelerator produced during
1388
01:51:36.020 --> 01:51:39.619
the era that gave us the Higgs discovery. The number
1389
01:51:39.659 --> 01:51:44.279
of individual proton collisions the upgraded machine will generate over
1390
01:51:44.359 --> 01:51:48.710
its lifetime is not a modest increase over what came before.
1391
01:51:49.470 --> 01:51:54.060
It is a different order of magnitude entirely. To achieve this,
1392
01:51:54.529 --> 01:51:59.989
engineers are replacing 1.2 kilometers of the accelerator's inner sections
1393
01:52:00.350 --> 01:52:04.470
with new magnets made from a material called niobium tin.
1394
01:52:05.109 --> 01:52:10.010
The magnets currently in place use niobium titanium. That was
1395
01:52:10.090 --> 01:52:15.720
already pushing the boundaries of what superconducting technology could reliably do.
1396
01:52:16.439 --> 01:52:21.789
Niobium tin can generate stronger magnetic fields. That means tighter
1397
01:52:21.829 --> 01:52:26.609
beam focus. That means more protons occupying a smaller space
1398
01:52:26.670 --> 01:52:30.930
when they cross paths, which means more collisions. The trade-off
1399
01:52:31.010 --> 01:52:34.789
is that niobium tin is harder to work with, more brittle,
1400
01:52:35.229 --> 01:52:39.270
more expensive to manufacture at the scale the upgrade requires.
1401
01:52:39.850 --> 01:52:43.909
It took years to develop the production process. The magnets
1402
01:52:43.970 --> 01:52:48.250
being installed now represent the leading edge of what superconducting
1403
01:52:48.310 --> 01:52:53.569
engineering can currently produce. Alongside the new magnets, the upgrade
1404
01:52:53.590 --> 01:52:58.689
is installing devices called crab cavities. The name sounds informal
1405
01:52:58.729 --> 01:53:03.949
for equipment this precise. Crab cavities are radio frequency structures
1406
01:53:04.010 --> 01:53:07.810
that tilt the proton beams slightly just before they collide,
1407
01:53:08.569 --> 01:53:12.439
rotating them so their oval cross sections align face to
1408
01:53:12.520 --> 01:53:16.159
face rather than edge to edge. The effect is that
1409
01:53:16.300 --> 01:53:19.300
more of each beam overlaps with the opposing beam at
1410
01:53:19.340 --> 01:53:24.319
the collision point. Without crab cavities, a significant fraction of
1411
01:53:24.380 --> 01:53:28.539
each bunch of protons simply passes by without hitting anything.
1412
01:53:29.239 --> 01:53:34.590
With them, the overlap, and therefore the collision rate, increases substantially.
1413
01:53:35.310 --> 01:53:39.489
It is a small geometric adjustment with a large physical consequence.
1414
01:53:40.109 --> 01:53:44.739
The detectors themselves are being rebuilt almost from scratch. The
1415
01:53:44.850 --> 01:53:49.489
ATLAS and CMS experiments are receiving new silicon tracking systems
1416
01:53:49.590 --> 01:53:53.090
designed to handle the far higher density of events the
1417
01:53:53.310 --> 01:53:58.800
HL-LHC will produce, at 10 times the collision rate. The
1418
01:53:58.859 --> 01:54:02.880
electronics that read out particle tracks have to work faster
1419
01:54:03.399 --> 01:54:07.890
and sort through more simultaneous data without losing the rare
1420
01:54:08.029 --> 01:54:13.520
signals buried inside it. New precision timing detectors will allow
1421
01:54:13.680 --> 01:54:18.520
scientists to separate events that happen in the same nanosecond,
1422
01:54:19.000 --> 01:54:23.600
but at slightly different positions along the beamline. A problem
1423
01:54:23.640 --> 01:54:28.250
that barely existed at current collision rates, but becomes significant
1424
01:54:28.289 --> 01:54:32.970
at the luminosities the HL-LHC will reach. These are not
1425
01:54:33.050 --> 01:54:38.979
incremental adjustments to existing systems. They're new instruments. All of
1426
01:54:39.029 --> 01:54:43.859
this matters because of where RUN3 left things. The penguin
1427
01:54:43.920 --> 01:54:49.460
decay measurements showed a disagreement with standard model predictions, not
1428
01:54:49.520 --> 01:54:53.279
a large enough disagreement to claim a discovery, but a
1429
01:54:53.380 --> 01:54:58.510
clean one and a consistent one across multiple analyses. The
1430
01:54:58.609 --> 01:55:04.590
matter-antimatter asymmetry results confirmed CP violation in baryons for the
1431
01:55:04.670 --> 01:55:08.369
first time. But the size of the effect measured is
1432
01:55:08.470 --> 01:55:12.460
still not enough to explain the universe's imbalance on its own.
1433
01:55:13.060 --> 01:55:17.520
The Higgs boson's self-coupling, the way the Higgs field interacts
1434
01:55:17.579 --> 01:55:21.399
with itself, the property that determined the shape of the
1435
01:55:21.500 --> 01:55:25.630
universe in its earliest moments, has not been measured at all.
1436
01:55:26.270 --> 01:55:31.069
It requires observing two Higgs bosons produced simultaneously in a
1437
01:55:31.229 --> 01:55:35.930
single collision. An event so rare that the entire Run3
1438
01:55:35.989 --> 01:55:40.439
dataset contained only a handful of candidates. None of these
1439
01:55:40.560 --> 01:55:44.020
questions can be answered with the data already on hand.
1440
01:55:44.600 --> 01:55:49.430
The HL-LHC was designed with exactly these questions in mind.
1441
01:55:50.250 --> 01:55:55.069
At 10 times the luminosity, the penguin decay sample grows
1442
01:55:55.149 --> 01:56:00.800
from hundreds of millions of events to billions. Statistical fluctuations
1443
01:56:00.859 --> 01:56:04.399
that could mimic a real signal at current data volumes
1444
01:56:04.479 --> 01:56:08.289
become visible for what they are. If the disagreement in
1445
01:56:08.369 --> 01:56:13.170
B-maison decays is a genuine signature of an undiscovered particle
1446
01:56:13.489 --> 01:56:17.449
interfering in the loop, more data will sharpen it into
1447
01:56:17.529 --> 01:56:21.800
something that crosses the 5-sigma threshold. If it is noise,
1448
01:56:22.319 --> 01:56:26.109
more data will wash it out. Either answer closes a
1449
01:56:26.170 --> 01:56:30.029
chapter that Run 3 could not close. The same logic
1450
01:56:30.069 --> 01:56:34.489
applies to the dark matter searches. The LHC hunts for
1451
01:56:34.550 --> 01:56:38.520
dark matter by looking for collisions where momentum goes missing,
1452
01:56:38.909 --> 01:56:42.819
where particles carry energy out of the detector without leaving
1453
01:56:42.899 --> 01:56:49.189
any trace. The HL-LHC will produce enough collisions to probe
1454
01:56:49.289 --> 01:56:54.250
production rates orders of magnitude smaller than anything the current
1455
01:56:54.289 --> 01:56:59.300
machine could reach, into mass ranges and coupling strengths that
1456
01:56:59.340 --> 01:57:04.640
were simply invisible before. The Higgs self-coupling measurement may be
1457
01:57:04.680 --> 01:57:09.979
the most consequential single number the HLLHC is being built
1458
01:57:10.060 --> 01:57:14.289
to find. In the standard model, that coupling has a
1459
01:57:14.369 --> 01:57:19.579
specific predicted value. If the measured value matches the prediction,
1460
01:57:20.079 --> 01:57:23.649
the Higgs sector is exactly what the theory says it is.
1461
01:57:24.350 --> 01:57:29.250
If it deviates, even slightly, it points to new physics
1462
01:57:29.329 --> 01:57:33.409
in the most fundamental part of the model, the mechanism
1463
01:57:33.489 --> 01:57:37.939
that gives mass to everything. Observing enough Higgs pairs to
1464
01:57:38.039 --> 01:57:43.579
measure the self-coupling precisely requires approximately the full data set
1465
01:57:43.640 --> 01:57:48.319
the HL-LHC is expected to produce over its entire planned
1466
01:57:48.380 --> 01:57:53.350
operational lifetime. It cannot be rushed. It cannot be done
1467
01:57:53.390 --> 01:57:59.409
with a smaller machine. The four-year shutdown, the $ 1. 5 billion,
1468
01:58:00.149 --> 01:58:04.569
the new magnets and crab cavities and detector systems, all
1469
01:58:04.590 --> 01:58:07.949
of it is aimed in part at this single measurement.
1470
01:58:08.550 --> 01:58:11.439
The scale of what is happening underground right now is
1471
01:58:11.560 --> 01:58:18.579
easy to understate. Thousands of engineers, physicists, technicians across dozens
1472
01:58:18.640 --> 01:58:23.260
of countries are coordinating a reconstruction project with tolerances measured
1473
01:58:23.279 --> 01:58:27.319
in fractions of a millimetre and timelines measured in years.
1474
01:58:27.960 --> 01:58:32.220
Every component being installed has to work at temperatures colder
1475
01:58:32.260 --> 01:58:37.149
than deep space. Every new detector system has to integrate
1476
01:58:37.199 --> 01:58:41.930
with software pipelines that will process more data per second
1477
01:58:41.989 --> 01:58:46.130
than most scientific instruments generate in a year. The work
1478
01:58:46.189 --> 01:58:50.229
is already underway. The expected restart is around 2030. The
1479
01:58:50.250 --> 01:58:52.409
upgrade is a $ 1. 5 billion bet that the anomalies are real.
1480
01:58:56.630 --> 01:58:59.590
that ten times more data will be enough to tell
1481
01:58:59.630 --> 01:59:04.100
the difference between a fluctuation and a discovery. If even
1482
01:59:04.260 --> 01:59:07.239
two or three of the current anomalies hold up under
1483
01:59:07.279 --> 01:59:11.520
the scrutiny of the high luminosity LHC, the standard model
1484
01:59:11.600 --> 01:59:15.630
as a complete description of nature is done. Not damaged,
1485
01:59:16.210 --> 01:59:20.390
not patched, done. That is not an overstatement. It is
1486
01:59:20.449 --> 01:59:24.689
what the logic demands. A theory that fails to predict
1487
01:59:24.789 --> 01:59:30.289
what experiments repeatedly observe is not a complete theory, and
1488
01:59:30.329 --> 01:59:34.890
the Standard Model has been failing in small, precise, consistent
1489
01:59:34.949 --> 01:59:39.210
ways for long enough that the pattern is difficult to ignore.
1490
01:59:40.050 --> 01:59:43.630
To understand what that actually means, it helps to be
1491
01:59:43.789 --> 01:59:47.170
clear about what the Standard Model is and is not.
1492
01:59:47.770 --> 01:59:50.930
It is not a guess. It is not a rough sketch.
1493
01:59:51.659 --> 01:59:55.090
It is one of the most precisely tested frameworks in
1494
01:59:55.130 --> 02:00:00.289
the history of science, confirmed across decades and across dozens
1495
02:00:00.350 --> 02:00:05.760
of independent experiments on multiple continents. Its predictions for things
1496
02:00:05.810 --> 02:00:09.819
like the magnetic moment of the electron match observations to
1497
02:00:09.819 --> 02:00:15.460
11 decimal places. 11. That is the kind of accuracy
1498
02:00:15.520 --> 02:00:18.979
that earns a theory the right to be taken seriously.
1499
02:00:19.739 --> 02:00:25.319
And yet, Underneath that extraordinary precision, the cracks are there.
1500
02:00:26.079 --> 02:00:30.899
The penguin decay measurements that don't line up. The matter-antimatter
1501
02:00:30.960 --> 02:00:35.079
asymmetry in baryons that exists but isn't large enough to
1502
02:00:35.159 --> 02:00:40.760
explain the universe we live in. The 2,100-day cycle problem,
1503
02:00:41.140 --> 02:00:45.439
in a different field, has a familiar shape, a clean
1504
02:00:45.520 --> 02:00:49.930
repeating signal that none of the standard explanations can account for.
1505
02:00:50.609 --> 02:00:54.840
In particle physics, several of those signals are stacking up
1506
02:00:54.899 --> 02:00:58.800
at once. Here is what physicists actually mean when they
1507
02:00:58.880 --> 02:01:02.880
talk about what comes next. If the anomalies are real,
1508
02:01:03.359 --> 02:01:06.920
the first question is whether they point toward new particles,
1509
02:01:07.680 --> 02:01:13.029
new forces, or new symmetries. And the answer matters, because
1510
02:01:13.189 --> 02:01:17.779
each possibility points to a different kind of revolution. New
1511
02:01:17.859 --> 02:01:23.079
particles alone would be significant but manageable. The standard model
1512
02:01:23.119 --> 02:01:28.210
could potentially be extended. New forces would be a deeper disruption.
1513
02:01:28.649 --> 02:01:33.789
The known forces, electromagnetism, the strong force, the weak force,
1514
02:01:34.289 --> 02:01:36.970
are built into the architecture of the theory at a
1515
02:01:37.109 --> 02:01:41.409
fundamental level. A fifth force, or a hidden sector of
1516
02:01:41.470 --> 02:01:47.020
forces operating between dark matter particles, would require rewriting that
1517
02:01:47.159 --> 02:01:52.460
architecture from the floor up. Then there is supersymmetry. For decades,
1518
02:01:52.560 --> 02:01:55.699
this has been the leading candidate theory for what lies
1519
02:01:55.779 --> 02:01:59.779
beyond the Standard Model. The basic idea is that every
1520
02:01:59.859 --> 02:02:04.310
particle we know has a partner particle, heavier and not
1521
02:02:04.369 --> 02:02:09.569
yet detected, related by a mathematical symmetry that connects fermions
1522
02:02:09.630 --> 02:02:15.229
and bosons. Supersymmetry is not a fringe idea. it solves
1523
02:02:15.369 --> 02:02:20.529
real problems. It provides a natural candidate for dark matter
1524
02:02:20.810 --> 02:02:25.250
in the form of the lightest supersymmetric particle, which would
1525
02:02:25.270 --> 02:02:30.869
be stable, massive and invisible to conventional detection. It helps
1526
02:02:30.970 --> 02:02:36.510
resolve certain mathematical instabilities in the Higgs boson mass. It
1527
02:02:36.609 --> 02:02:40.890
points toward a unification of forces at very high energies
1528
02:02:40.970 --> 02:02:44.229
in a way that the standard model alone cannot achieve.
1529
02:02:45.020 --> 02:02:49.640
The theory has a serious pedigree and serious supporters. The
1530
02:02:49.699 --> 02:02:52.880
problem is that the LHC has not found any of it.
1531
02:02:53.460 --> 02:02:57.680
Run 1, Run 2, and now Run 3 have pushed
1532
02:02:57.739 --> 02:03:02.899
the lower bound on supersymmetric particle masses progressively higher than
1533
02:03:02.930 --> 02:03:06.250
the most natural versions of the theory, the ones that
1534
02:03:06.289 --> 02:03:11.250
predicted particles within reach of the LHC, are effectively ruled out.
1535
02:03:12.029 --> 02:03:17.300
Supersymmetry is not dead. but it is considerably less comfortable
1536
02:03:17.340 --> 02:03:21.619
than it was 15 years ago. Extra dimensions are a
1537
02:03:21.699 --> 02:03:27.649
separate class of possibility. Some theoretical frameworks predict that space
1538
02:03:27.729 --> 02:03:31.590
has more than three dimensions, but that the additional ones
1539
02:03:31.670 --> 02:03:36.020
are curled up so tightly at such small scales that
1540
02:03:36.029 --> 02:03:41.079
they are undetectable under ordinary conditions. At the energy scales
1541
02:03:41.119 --> 02:03:46.510
the LHC reaches, These hidden dimensions might produce detectable effects,
1542
02:03:47.050 --> 02:03:51.239
gravitons leaking into them, energy going missing in ways that
1543
02:03:51.300 --> 02:03:57.079
don't match any known process. Nothing like that has been observed. Again,
1544
02:03:57.680 --> 02:04:01.819
not ruled out entirely. But the easy versions of the
1545
02:04:01.939 --> 02:04:06.189
idea are gone. Whatever new physics is out there, it
1546
02:04:06.250 --> 02:04:09.909
is not sitting in the obvious places the theorists pointed
1547
02:04:09.989 --> 02:04:15.079
to first. this is the honest position the standard model
1548
02:04:15.140 --> 02:04:19.800
has cracks the most popular theories designed to explain those
1549
02:04:19.899 --> 02:04:23.039
cracks have not shown up in the data that leaves
1550
02:04:23.140 --> 02:04:28.359
physicists in an uncomfortable place the existing framework is clearly
1551
02:04:28.439 --> 02:04:33.380
incomplete the proposed replacements are under serious pressure and the
1552
02:04:33.439 --> 02:04:37.000
thing that actually replaces it may not have been written
1553
02:04:37.079 --> 02:04:41.539
down yet physics has been in this situation before In
1554
02:04:41.579 --> 02:04:46.060
the late 19th century classical mechanics was the most successful
1555
02:04:46.180 --> 02:04:51.039
physical theory ever constructed and physicists believed they were close
1556
02:04:51.100 --> 02:04:56.380
to a final description of nature. Then came the ultraviolet catastrophe,
1557
02:04:56.800 --> 02:05:01.970
the photoelectric effect, the strange behavior of electrons in atoms.
1558
02:05:02.739 --> 02:05:07.390
None of those anomalies fit the existing framework. The theory
1559
02:05:07.430 --> 02:05:12.529
that resolved them, quantum mechanics, was not an extension of
1560
02:05:12.609 --> 02:05:17.689
classical physics. It was a replacement, a different kind of
1561
02:05:17.810 --> 02:05:22.739
logic operating underneath a surface that had looked smooth. The
1562
02:05:22.800 --> 02:05:26.079
question now is whether the anomalies piling up at the
1563
02:05:26.239 --> 02:05:31.399
LHC are the ultraviolet catastrophe of this era. The honest
1564
02:05:31.560 --> 02:05:35.829
answer is that nobody knows. Physics has also been through
1565
02:05:35.930 --> 02:05:41.210
periods where anomalies gathered, Theories proliferated, and then more data
1566
02:05:41.289 --> 02:05:47.210
arrived and the anomalies dissolved. The 3.5 kV X-ray line
1567
02:05:47.250 --> 02:05:51.789
that appeared in galaxy cluster spectra for years and generated
1568
02:05:51.869 --> 02:05:58.420
enormous theoretical interest eventually faded as data quality improved. Anomalies
1569
02:05:58.479 --> 02:06:02.340
in B meson decays that briefly looked like evidence of
1570
02:06:02.420 --> 02:06:08.420
lepton universality violations. have been revised downward with better measurements.
1571
02:06:09.260 --> 02:06:13.000
The history of particle physics is partly a history of
1572
02:06:13.119 --> 02:06:17.760
phantom discoveries. This is not a criticism. It is how
1573
02:06:17.819 --> 02:06:23.229
the process works. You take signals seriously, you test them harder,
1574
02:06:23.630 --> 02:06:26.470
and you find out whether they were real. What is
1575
02:06:26.529 --> 02:06:31.069
different now is precision. The penguin decay results are not
1576
02:06:31.130 --> 02:06:35.130
a single anomaly from a single experiment in a single run.
1577
02:06:35.600 --> 02:06:39.979
They are a pattern measured repeatedly across different decay channels
1578
02:06:40.399 --> 02:06:46.600
with systematic uncertainties that have been carefully characterized. The matter-antimatter
1579
02:06:46.659 --> 02:06:51.750
results in baryons represent the first observation of CP violation
1580
02:06:52.029 --> 02:06:56.369
in that class of particles after years of dedicated searching.
1581
02:06:57.069 --> 02:07:01.600
These are not flukes in noisy data. They are consistent,
1582
02:07:01.939 --> 02:07:06.949
reproducible measurements that disagree with predictions in ways that grow
1583
02:07:07.090 --> 02:07:12.470
harder to dismiss as statistics accumulate. When the high luminosity
1584
02:07:12.689 --> 02:07:17.649
LHC delivers 10 times more data, those measurements will sharpen
1585
02:07:17.710 --> 02:07:23.239
into either confirmations or contradictions. There will be no middle ground.
1586
02:07:23.800 --> 02:07:27.699
Either the discrepancies hold and the standard model is fractured
1587
02:07:27.739 --> 02:07:31.920
at its foundations, or they wash out and the model survives.
1588
02:07:32.470 --> 02:07:38.500
battered but intact. The theoretical community is not waiting. Right now,
1589
02:07:38.979 --> 02:07:43.500
papers are being written on lepto-quarks, particles that interact with
1590
02:07:43.619 --> 02:07:48.500
both quarks and leptons, which the standard model forbids but
1591
02:07:48.539 --> 02:07:52.640
which could naturally produce the patterns seen in certain B
1592
02:07:52.640 --> 02:07:57.409
meson decays. Papers are being written on Z' prime bosons,
1593
02:07:58.090 --> 02:08:02.350
hypothetical heavy cousins of the Z boson that could mediate
1594
02:08:02.510 --> 02:08:07.560
new forces between standard model particles. Papers are being written
1595
02:08:07.640 --> 02:08:13.720
on dark photons, on composite Higgs models, on extended gauge symmetries.
1596
02:08:14.460 --> 02:08:19.039
Each of these frameworks makes predictions specific enough to be tested.
1597
02:08:19.920 --> 02:08:24.039
Some of them predict particles that the high luminosity LHC
1598
02:08:24.079 --> 02:08:26.640
should be able to produce if they exist at the
1599
02:08:26.699 --> 02:08:32.800
right mass range. When Run-4 data starts coming in after 2030,
1600
02:08:32.800 --> 02:08:36.600
these theories will either gain traction or lose it, and
1601
02:08:36.640 --> 02:08:40.399
the field will start to converge. But here is what
1602
02:08:40.500 --> 02:08:44.800
keeps the more careful theorists up at night. Every major
1603
02:08:44.859 --> 02:08:48.510
revolution in physics arrived with a hint that the answer
1604
02:08:48.550 --> 02:08:53.560
was something new. not just an extension of the existing vocabulary.
1605
02:08:54.310 --> 02:09:00.350
Quantum mechanics did not look like corrected classical mechanics. Relativity
1606
02:09:00.409 --> 02:09:04.829
did not look like corrected Newtonian gravity. They looked like
1607
02:09:04.970 --> 02:09:10.680
different rules. The possibility that whatever is generating these anomalies
1608
02:09:11.239 --> 02:09:14.899
follows a logic that physicists have not yet developed the
1609
02:09:14.939 --> 02:09:20.010
language to describe is not a remote one. The LHC
1610
02:09:20.090 --> 02:09:24.369
is finding things that don't fit. The theories designed to
1611
02:09:24.430 --> 02:09:29.420
explain things that don't fit are themselves not fitting. That
1612
02:09:29.479 --> 02:09:33.380
recursive problem is either a sign that the theorists haven't
1613
02:09:33.439 --> 02:09:37.180
been creative enough yet, or a sign that the answer
1614
02:09:37.260 --> 02:09:41.029
is going to require a new kind of creativity entirely.
1615
02:09:41.890 --> 02:09:46.050
The history is clear on one point. Paradigm shifts in
1616
02:09:46.119 --> 02:09:51.069
physics do not announce themselves in advance. They arrive through
1617
02:09:51.130 --> 02:09:58.689
exactly this kind of process. Precise measurement, persistent anomaly, failure
1618
02:09:58.750 --> 02:10:02.600
of existing frameworks to explain it, and then eventually a
1619
02:10:02.739 --> 02:10:07.100
new idea that makes the anomaly obvious in retrospect. The
1620
02:10:07.220 --> 02:10:11.880
measurement is already happening. The anomalies are already on the table.
1621
02:10:12.460 --> 02:10:16.340
The most unsettling possibility is not that the new physics
1622
02:10:16.439 --> 02:10:20.479
turns out to be supersymmetry or extra dimensions or any
1623
02:10:20.529 --> 02:10:24.350
of the well-theorized candidates. It is that it turns out
1624
02:10:24.409 --> 02:10:28.789
to be something nobody has written down yet. Step back
1625
02:10:28.850 --> 02:10:33.420
from the individual discoveries and a stranger picture comes into focus.
1626
02:10:34.159 --> 02:10:40.180
Every exotic particle, every anomalous decay, every measurement that sits
1627
02:10:40.279 --> 02:10:43.430
in tension with the standard model. These have been the
1628
02:10:43.529 --> 02:10:48.310
focus for the last several sections. They are genuinely important.
1629
02:10:49.069 --> 02:10:52.619
But they are all operating inside a small corner of
1630
02:10:52.680 --> 02:10:57.180
a much larger problem. Pull the camera back far enough
1631
02:10:57.340 --> 02:11:00.100
and the real scale of what physics does not yet
1632
02:11:00.199 --> 02:11:04.710
understand becomes almost difficult to hold in your head at once.
1633
02:11:05.630 --> 02:11:08.569
The standard model accounts for roughly 5% of the universe.
1634
02:11:10.550 --> 02:11:13.149
That is not a rough estimate or a figure that
1635
02:11:13.229 --> 02:11:16.979
scientists expect to revise upwards slightly once they fill in
1636
02:11:17.020 --> 02:11:21.159
a few gaps. It is a hard number, arrived at
1637
02:11:21.199 --> 02:11:28.090
through decades of independent measurements from telescopes, cosmic microwave background surveys,
1638
02:11:28.560 --> 02:11:34.369
and gravitational studies of galaxy clusters. The universe contains something.
1639
02:11:34.989 --> 02:11:39.020
The Standard Model describes a fraction of it. The remaining
1640
02:11:39.020 --> 02:11:45.680
95% sits completely outside the theory's reach, not because physicists
1641
02:11:45.720 --> 02:11:49.500
haven't looked, but because the model was never built to
1642
02:11:49.619 --> 02:11:54.369
see it. Dark matter makes up about 27% of the
1643
02:11:54.489 --> 02:11:59.710
universe's total energy content. It does not emit light. It
1644
02:11:59.750 --> 02:12:03.409
does not absorb light. It does not interact with the
1645
02:12:03.470 --> 02:12:08.039
electromagnetic force at all. which means every detector built around
1646
02:12:08.100 --> 02:12:12.979
electromagnetic signals, which is most of them, is essentially blind
1647
02:12:13.060 --> 02:12:17.640
to it. What dark matter does do is pull. Its
1648
02:12:17.680 --> 02:12:22.050
gravitational influence shows up in the behavior of galaxies, in
1649
02:12:22.090 --> 02:12:26.310
the way clusters of galaxies bend light from objects behind them,
1650
02:12:27.010 --> 02:12:31.090
and in the large-scale structure of the universe itself. The
1651
02:12:31.170 --> 02:12:35.010
maps of where matter is concentrated in the cosmos match
1652
02:12:35.050 --> 02:12:40.689
a dark matter distribution with extraordinary precision. Something is there.
1653
02:12:41.350 --> 02:12:46.449
It has mass. It shapes the universe. The Standard Model
1654
02:12:46.529 --> 02:12:50.770
has no particle that fits this description. No field that
1655
02:12:50.829 --> 02:12:55.470
produces it. No mechanism that generates it. It simply does
1656
02:12:55.630 --> 02:13:00.350
not appear anywhere in the theory. Dark energy is stranger still.
1657
02:13:01.029 --> 02:13:07.359
In 1998, Two independent teams of astronomers studying distant supernovae
1658
02:13:07.680 --> 02:13:11.739
discovered that the expansion of the universe is not slowing down.
1659
02:13:12.260 --> 02:13:17.229
It is speeding up. Space itself is accelerating outward, driven
1660
02:13:17.289 --> 02:13:20.449
by something built into the fabric of the universe that
1661
02:13:20.550 --> 02:13:26.529
pushes everything apart. This something, dark energy, makes up roughly
1662
02:13:26.529 --> 02:13:31.750
68% of the universe's total energy content. It is the
1663
02:13:31.890 --> 02:13:37.229
dominant constituent of everything that exists. And like dark matter,
1664
02:13:37.689 --> 02:13:42.289
it appears nowhere in the standard model. There is no particle,
1665
02:13:42.840 --> 02:13:47.180
no force carrier, no field in the theory that corresponds
1666
02:13:47.260 --> 02:13:52.380
to it. Some physicists associate dark energy with what Einstein
1667
02:13:52.439 --> 02:13:56.880
called the cosmological constant, a term he added to his
1668
02:13:56.939 --> 02:14:01.159
equations and later called his greatest mistake. and which turns
1669
02:14:01.239 --> 02:14:05.630
out to describe reality more accurately than he was comfortable admitting.
1670
02:14:06.250 --> 02:14:10.149
But connecting that constant to a physical mechanism remains one
1671
02:14:10.189 --> 02:14:14.510
of the deepest unsolved problems in all of science. Add
1672
02:14:14.550 --> 02:14:18.109
those numbers together, dark energy at 68%, dark matter at 27%,
1673
02:14:18.109 --> 02:14:27.319
that accounts for 95% of the universe. The Standard Model,
1674
02:14:27.600 --> 02:14:31.319
the most precisely tested theory in the history of science,
1675
02:14:31.760 --> 02:14:35.729
confirmed to 11 decimal places in some of its predictions,
1676
02:14:36.399 --> 02:14:41.590
describes the remaining 5%. This is not a small embarrassment.
1677
02:14:42.350 --> 02:14:46.069
It is a fundamental statement about the limits of the theory.
1678
02:14:46.729 --> 02:14:50.550
The thing physicists sometimes call the best theory ever written
1679
02:14:51.149 --> 02:14:54.930
is a description of a thin slice of reality and
1680
02:14:54.949 --> 02:14:59.989
the slice it misses is almost everything. Then there is gravity.
1681
02:15:00.670 --> 02:15:04.569
The standard model describes three of the four fundamental forces.
1682
02:15:05.359 --> 02:15:09.760
The strong force holds quarks together inside protons and neutrons.
1683
02:15:10.319 --> 02:15:15.340
The weak force governs radioactive decay and certain particle transformations.
1684
02:15:16.100 --> 02:15:21.909
Electromagnetism governs light, electricity, and the behavior of charged particles.
1685
02:15:22.649 --> 02:15:25.989
Gravity is the fourth force. It is the one every
1686
02:15:26.090 --> 02:15:30.210
person on Earth feels every moment of their life. It
1687
02:15:30.270 --> 02:15:33.909
is the force that holds the Moon in orbit, collapses
1688
02:15:34.029 --> 02:15:39.399
gas clouds into stars, and pulls galaxies into clusters. And
1689
02:15:39.479 --> 02:15:44.739
it is completely absent from the Standard Model. Not poorly described,
1690
02:15:45.239 --> 02:15:51.970
not approximately handled, absent. The mathematical framework of quantum field theory,
1691
02:15:52.350 --> 02:15:55.510
on which the entire Standard Model is built, and the
1692
02:15:55.550 --> 02:16:02.069
mathematical framework of general relativity, which describes gravity, are not compatible.
1693
02:16:02.489 --> 02:16:09.109
They use different geometries, different assumptions, different mathematical languages. Every
1694
02:16:09.189 --> 02:16:13.029
attempt to quantize gravity, to write down a theory of
1695
02:16:13.130 --> 02:16:17.130
gravitons and gravitational fields in the same way the standard
1696
02:16:17.210 --> 02:16:22.770
model describes photons and gluons, runs into infinities that cannot
1697
02:16:22.850 --> 02:16:28.590
be removed. equations break, something about the way we understand space,
1698
02:16:28.729 --> 02:16:33.790
time and quantum mechanics at the smallest scales is fundamentally wrong,
1699
02:16:34.389 --> 02:16:39.780
or at least fundamentally incomplete. A truly unified theory would
1700
02:16:39.860 --> 02:16:43.700
need to do something that no theory has yet managed.
1701
02:16:44.479 --> 02:16:47.739
It would need to describe all four forces within a
1702
02:16:47.879 --> 02:16:52.700
single mathematical framework, It would need to generate a dark
1703
02:16:52.840 --> 02:16:57.700
matter candidate from first principles, a particle that has mass
1704
02:16:58.000 --> 02:17:03.139
that interacts gravitationally and that does not couple to electromagnetism.
1705
02:17:03.879 --> 02:17:07.879
It would need to explain why dark energy exists and
1706
02:17:07.940 --> 02:17:10.950
why it has the value it has, rather than a
1707
02:17:11.069 --> 02:17:15.670
value billions of times larger, which is what naive quantum
1708
02:17:15.729 --> 02:17:21.520
calculations predict. It would need to explain the matter-antimatter asymmetry,
1709
02:17:22.020 --> 02:17:26.420
why one extra particle of matter existed per billion pairs
1710
02:17:26.500 --> 02:17:29.930
in the early universe. And it would need to do
1711
02:17:30.209 --> 02:17:35.329
all of this while reproducing every successful prediction the Standard
1712
02:17:35.409 --> 02:17:40.229
Model already makes, without disturbing any of the results that
1713
02:17:40.270 --> 02:17:45.809
have been confirmed to extraordinary precision. That is an enormous
1714
02:17:45.889 --> 02:17:50.760
set of requirements. theories exist that attempt to of it.
1715
02:17:51.420 --> 02:17:56.540
Supersymmetry adds a partner particle to every known particle, and
1716
02:17:56.620 --> 02:18:02.120
in some versions produces a dark matter candidate naturally. String
1717
02:18:02.180 --> 02:18:06.760
theory attempts to unify gravity with the quantum forces by
1718
02:18:06.879 --> 02:18:13.520
treating particles as vibrating strings in extra dimensions. Loop quantum
1719
02:18:13.579 --> 02:18:18.989
gravity tries to quantize space-time itself. None of these has
1720
02:18:19.069 --> 02:18:24.129
produced a confirmed experimental prediction that distinguishes it from the
1721
02:18:24.229 --> 02:18:28.600
standard model. None has been tested and found to match
1722
02:18:28.680 --> 02:18:32.479
observations in a way that compels physicists to accept it.
1723
02:18:33.219 --> 02:18:38.319
They are frameworks, not yet confirmed theories, and the gap
1724
02:18:38.440 --> 02:18:43.610
between a compelling mathematical structure and a tested physical theory
1725
02:18:44.030 --> 02:18:48.309
is wider than it sometimes looks from the outside. Every
1726
02:18:48.370 --> 02:18:52.069
discovery that has come out of CERN, the Higgs boson,
1727
02:18:52.329 --> 02:18:57.770
the exotic hadrons, the CP violation in baryons, the anomalies
1728
02:18:57.829 --> 02:19:02.270
in penguin decays, is real data about the 5% the
1729
02:19:02.329 --> 02:19:07.670
standard model does cover. These are genuine advances. They sharpen
1730
02:19:07.729 --> 02:19:11.909
our picture of how quarks behave, how the Higgs field operates,
1731
02:19:12.409 --> 02:19:15.750
how matter and antimatter differ. But they are pieces of
1732
02:19:15.770 --> 02:19:19.129
a puzzle where the majority of the image is still missing.
1733
02:19:19.629 --> 02:19:23.909
The frame exists. The corner pieces are mostly in place.
1734
02:19:24.729 --> 02:19:27.809
The section in the middle, the part that fills most
1735
02:19:27.870 --> 02:19:32.049
of the board, has barely been started. What the next
1736
02:19:32.110 --> 02:19:35.920
generation of experiments needs to do is find a way
1737
02:19:35.979 --> 02:19:41.260
into that missing territory. The high luminosity LHC is not
1738
02:19:41.440 --> 02:19:45.340
built to detect dark energy. It was not designed to
1739
02:19:45.399 --> 02:19:49.590
solve quantum gravity, but it can search for particles that
1740
02:19:49.670 --> 02:19:52.860
might hint at what dark matter is made of. It
1741
02:19:52.899 --> 02:19:57.440
can measure the Higgs field's self-interaction with enough precision to
1742
02:19:57.500 --> 02:20:01.909
look for deviations that point towards something beyond. It can
1743
02:20:01.969 --> 02:20:06.110
confirm or rule out the anomalies that currently sit just
1744
02:20:06.209 --> 02:20:10.969
below discovery threshold. Each of those results is another clue,
1745
02:20:11.610 --> 02:20:16.059
and in a puzzle this large, every clue counts. The
1746
02:20:16.180 --> 02:20:20.940
theory that scientists have spent 50 years building, testing and
1747
02:20:21.000 --> 02:20:28.350
defending with extraordinary precision describes, at best, one twentieth of
1748
02:20:28.430 --> 02:20:33.370
what the universe actually contains, and the other nineteen twentieths
1749
02:20:33.469 --> 02:20:38.489
are still waiting to be explained. Every few years, someone
1750
02:20:38.530 --> 02:20:42.889
with a reasonable question asks, Why billions of dollars are
1751
02:20:42.909 --> 02:20:47.190
being spent to smash particles together in a tunnel under Switzerland?
1752
02:20:47.889 --> 02:20:52.129
It is a fair question. The LHC cost roughly 10
1753
02:20:52.129 --> 02:20:55.840
billion dollars to build and operates on an annual budget
1754
02:20:56.379 --> 02:21:01.319
that could fund hospitals, schools or climate research. The people
1755
02:21:01.459 --> 02:21:05.540
asking are not wrong to ask. The answer requires going
1756
02:21:05.620 --> 02:21:11.809
back further than most people expect. In 1897, JJ Thompson
1757
02:21:11.840 --> 02:21:16.049
discovered the electron. He was not trying to invent anything.
1758
02:21:16.770 --> 02:21:20.750
He was trying to understand what cathode rays actually were.
1759
02:21:21.829 --> 02:21:27.969
The practical applications of that discovery, every circuit board, every screen,
1760
02:21:28.110 --> 02:21:33.649
every medical imaging device that uses electron beams, were completely
1761
02:21:33.709 --> 02:21:37.770
invisible from where Thompson was standing. He had no way
1762
02:21:37.829 --> 02:21:42.090
of knowing He was just following the question. The same
1763
02:21:42.170 --> 02:21:46.209
pattern repeated with nuclear physics in the early 20th century.
1764
02:21:46.899 --> 02:21:50.260
Rutherford and his colleagues mapped the structure of the atom
1765
02:21:50.299 --> 02:21:55.280
without any intention of producing nuclear power or nuclear medicine.
1766
02:21:55.920 --> 02:22:01.129
The applications emerged decades later as a consequence of understanding
1767
02:22:01.209 --> 02:22:06.670
something fundamental. This is how foundational physics has always worked.
1768
02:22:07.430 --> 02:22:11.000
You cannot see the application from the beginning, because the
1769
02:22:11.040 --> 02:22:16.219
beginning is about understanding, not building. The World Wide Web
1770
02:22:16.280 --> 02:22:21.579
was invented at CERN in 1989. Tim Berners-Lee was trying
1771
02:22:21.620 --> 02:22:25.729
to solve a specific problem. How to share data between
1772
02:22:25.809 --> 02:22:30.090
physicists spread across dozens of countries who needed access to
1773
02:22:30.129 --> 02:22:34.889
the same experimental results. The solution he wrote was not
1774
02:22:34.989 --> 02:22:40.049
designed to become the primary infrastructure of global communication and commerce.
1775
02:22:40.610 --> 02:22:43.760
It was designed to help physicists talk to each other.
1776
02:22:44.159 --> 02:22:49.200
The Internet, as most people experience it today, descended directly
1777
02:22:49.260 --> 02:22:53.870
from a tool built to support particle physics research. Nobody
1778
02:22:53.950 --> 02:22:58.909
planned that. It happened because the research required solving problems
1779
02:22:58.989 --> 02:23:03.309
at a scale and complexity that drove engineering in directions
1780
02:23:03.370 --> 02:23:07.549
it would not otherwise have gone. The same dynamic applies
1781
02:23:07.610 --> 02:23:12.479
to medical imaging. MRI technology relies on the physics of
1782
02:23:12.610 --> 02:23:17.719
nuclear magnetic resonance, a phenomenon that was studied purely for
1783
02:23:17.780 --> 02:23:22.379
its scientific interest decades before anyone suggested it might be
1784
02:23:22.579 --> 02:23:27.559
used to look inside a living body. Particle accelerators themselves
1785
02:23:27.620 --> 02:23:32.889
are now used in cancer treatment. Proton therapy, which targets
1786
02:23:33.030 --> 02:23:37.209
tumors with beams of protons, uses technology that is a
1787
02:23:37.290 --> 02:23:43.059
direct descendant of accelerator physics developed at research institutions that
1788
02:23:43.100 --> 02:23:48.600
were asking purely theoretical questions about atomic structure. These are
1789
02:23:48.700 --> 02:23:53.459
not coincidences. are what happens when you fund the serious
1790
02:23:53.559 --> 02:23:58.590
investigation of how nature works. The specific discoveries coming out
1791
02:23:58.649 --> 02:24:03.069
of CERN carry their own long-range implications, even if they
1792
02:24:03.129 --> 02:24:07.250
are harder to trace right now. Understanding the Higgs field,
1793
02:24:07.809 --> 02:24:12.139
what it is, how it interacts with particles of different generations,
1794
02:24:12.600 --> 02:24:17.920
whether its self-coupling matches predictions, matters because the Higgs field
1795
02:24:18.059 --> 02:24:21.760
fills all of space. It is not a particle that
1796
02:24:21.840 --> 02:24:25.000
exists in one place. It is a property of the
1797
02:24:25.159 --> 02:24:29.299
universe itself, and the shape of that field determines why
1798
02:24:29.399 --> 02:24:33.100
matter has mass at all. If the Higgs behaves differently
1799
02:24:33.159 --> 02:24:37.309
than the Standard Model predicts, that difference is information about
1800
02:24:37.340 --> 02:24:41.270
the structure of reality at its most basic level. What
1801
02:24:41.309 --> 02:24:45.229
you do with that information is a question for later generations.
1802
02:24:45.750 --> 02:24:49.090
The pattern suggests they will find something to do with it.
1803
02:24:49.549 --> 02:24:55.239
the matter-antimatter asymmetry carries a more pointed implication. One extra
1804
02:24:55.270 --> 02:24:58.959
particle of matter per billion pairs is what allowed the
1805
02:24:59.100 --> 02:25:03.879
universe to exist. If the asymmetry had been slightly different,
1806
02:25:04.459 --> 02:25:10.079
there would be no stars, no planets, no chemistry, no biology.
1807
02:25:11.000 --> 02:25:17.370
Understanding exactly why the asymmetry exists What physical process tipped
1808
02:25:17.430 --> 02:25:20.989
the scales in the first fraction of a second is
1809
02:25:21.069 --> 02:25:24.969
not just an academic exercise. It is an attempt to
1810
02:25:25.049 --> 02:25:29.950
explain the necessary condition for everything that followed. Whether that
1811
02:25:30.030 --> 02:25:35.110
understanding ever translates into a practical technology is genuinely unknown.
1812
02:25:35.989 --> 02:25:39.170
But the asymmetry is one of the deepest facts about
1813
02:25:39.250 --> 02:25:42.409
why the universe is the way it is. and the
1814
02:25:42.569 --> 02:25:48.649
LHCb results measuring CP violation in baryons moved the explanation
1815
02:25:48.870 --> 02:25:53.079
one step closer. Dark matter is harder to connect to
1816
02:25:53.180 --> 02:25:59.420
everyday life, but the reasoning holds. Roughly 27% of the
1817
02:25:59.579 --> 02:26:03.860
universe is made of something that does not appear anywhere
1818
02:26:03.979 --> 02:26:08.829
in the most successful theory of matter ever written. Galaxies
1819
02:26:08.889 --> 02:26:13.489
could not hold their shape without it. The large-scale structure
1820
02:26:13.549 --> 02:26:18.270
of the cosmos, the way galaxies cluster into filaments and walls,
1821
02:26:18.729 --> 02:26:23.489
was shaped by dark matter's gravitational influence long before any
1822
02:26:23.590 --> 02:26:27.450
stars formed. Whatever it turns out to be, it is
1823
02:26:27.590 --> 02:26:31.629
not a minor addendum to physics. It is a dominant
1824
02:26:31.729 --> 02:26:37.170
feature of reality. Finding it, naming it, understanding how it
1825
02:26:37.250 --> 02:26:41.489
interacts even weakly with ordinary matter, would be among the
1826
02:26:41.629 --> 02:26:46.850
largest scientific discoveries in history. And the search is ongoing
1827
02:26:47.350 --> 02:26:52.860
at CERN and at detectors buried deep underground on multiple continents.
1828
02:26:53.700 --> 02:26:56.620
There is also an argument that does not depend on
1829
02:26:56.760 --> 02:27:01.129
future applications at all. The question of what the universe
1830
02:27:01.209 --> 02:27:04.950
is made of and what rules it operates by is
1831
02:27:05.010 --> 02:27:08.969
not a technical question that only specialists should care about.
1832
02:27:09.620 --> 02:27:12.940
It is the oldest and most serious version of a
1833
02:27:13.020 --> 02:27:17.260
question humans have been asking in every culture and every era.
1834
02:27:17.969 --> 02:27:21.670
What is this place? What is it made of? Why
1835
02:27:21.709 --> 02:27:25.590
does it behave the way it does? Particle physics is
1836
02:27:25.629 --> 02:27:29.709
the most rigorous attempt to answer those questions with precision
1837
02:27:29.790 --> 02:27:34.379
and evidence rather than assumption. The standard model is not
1838
02:27:34.440 --> 02:27:37.799
a philosophy. It is a set of equations that have
1839
02:27:37.840 --> 02:27:42.299
been tested to extraordinary accuracy and have held up against
1840
02:27:42.540 --> 02:27:47.299
every experimental challenge thrown at them for 50 years. And
1841
02:27:47.379 --> 02:27:51.049
it is still incomplete. The edge of what that model
1842
02:27:51.090 --> 02:27:55.870
can explain is the current frontier of human understanding. The
1843
02:27:55.930 --> 02:27:59.899
people working at CERN number in the thousands are They
1844
02:27:59.959 --> 02:28:03.680
come from more than a hundred countries. They speak dozens
1845
02:28:03.750 --> 02:28:07.510
of languages. They are united by a set of shared
1846
02:28:07.629 --> 02:28:12.389
questions about particles and forces and fields that most of
1847
02:28:12.450 --> 02:28:16.930
their families find difficult to understand at dinner. The research
1848
02:28:16.969 --> 02:28:22.280
has no military application, no immediate commercial value, and no
1849
02:28:22.360 --> 02:28:27.069
guaranteed payoff. It is funded by governments that have collectively
1850
02:28:27.129 --> 02:28:32.059
decided the questions are worth asking. That decision reflects something
1851
02:28:32.120 --> 02:28:36.159
about what science is actually for. Not only the production
1852
02:28:36.200 --> 02:28:41.139
of useful technologies, but the systematic expansion of what humanity
1853
02:28:41.239 --> 02:28:45.069
knows about the place it inhabits. The answer has always
1854
02:28:45.129 --> 02:28:49.229
been the same, because the rules of reality are worth knowing,
1855
02:28:49.870 --> 02:28:54.780
even before we know what to do with them. Around 2030,
1856
02:28:54.780 --> 02:28:59.520
the first new proton beams will circulate through the upgraded machine,
1857
02:29:00.219 --> 02:29:04.860
and the most sensitive particle physics experiment in history will begin.
1858
02:29:05.719 --> 02:29:09.799
The high luminosity LHC will not be a different machine
1859
02:29:09.860 --> 02:29:14.540
in name only. The niobium tin magnets being installed right
1860
02:29:14.659 --> 02:29:18.879
now will push the magnetic fields beyond what the original
1861
02:29:19.000 --> 02:29:23.979
superconducting coils could sustain. The crab cavities will tilt the
1862
02:29:24.040 --> 02:29:30.530
proton bunches just before collision, squeezing more interactions into every crossing.
1863
02:29:31.090 --> 02:29:34.629
The result is roughly 10 times the collision rate the
1864
02:29:34.709 --> 02:29:39.909
original machine could achieve. That is not an incremental improvement.
1865
02:29:40.430 --> 02:29:44.829
That is a different category of instrument. What that luminosity
1866
02:29:45.010 --> 02:29:50.579
actually buys is specificity. The penguin decay anomalies that came
1867
02:29:50.639 --> 02:29:56.159
out of Run 3 were measured across roughly 650 billion
1868
02:29:56.360 --> 02:30:01.879
B meson events. The high luminosity era will produce datasets
1869
02:30:01.879 --> 02:30:08.209
15 times larger. The statistical significance of those deviations, the
1870
02:30:08.290 --> 02:30:11.329
gap between what the standard model predicts and what the
1871
02:30:11.389 --> 02:30:17.190
detectors recorded, will either grow or disappear. There is no
1872
02:30:17.290 --> 02:30:22.309
middle outcome. If the anomaly was a fluctuation, More data
1873
02:30:22.329 --> 02:30:25.870
will wash it out. If something real is interfering in
1874
02:30:25.930 --> 02:30:31.079
those decays, something the standard model cannot account for, the
1875
02:30:31.219 --> 02:30:35.659
signal will sharpen into a discovery. Physicists have been in
1876
02:30:35.700 --> 02:30:40.399
this position before, watching a hint sit just below 5 sigma,
1877
02:30:40.920 --> 02:30:45.340
not knowing whether to trust it. The HLLHC is being
1878
02:30:45.459 --> 02:30:51.030
built to resolve exactly that uncertainty. The Higgs self-coupling measurement
1879
02:30:51.129 --> 02:30:54.610
is in the same position. The strength with which the
1880
02:30:54.649 --> 02:30:57.829
Higgs field interacts with itself is one of the most
1881
02:30:57.989 --> 02:31:03.450
fundamental unmeasured quantities in particle physics. It sets the shape
1882
02:31:03.510 --> 02:31:07.930
of the Higgs potential, the mathematical landscape that determines how
1883
02:31:07.989 --> 02:31:12.729
the field behaves across all of space. In the early universe,
1884
02:31:13.170 --> 02:31:17.059
that potential governed the transition out of the hot symmetric
1885
02:31:17.170 --> 02:31:21.079
state and into the broken symmetry state we live in now.
1886
02:31:21.879 --> 02:31:26.030
Whether that transition was smooth or violent, whether it created
1887
02:31:26.090 --> 02:31:31.489
conditions favorable for the matter-antimatter imbalance, depends on that coupling.
1888
02:31:32.110 --> 02:31:35.409
Run 3 could not measure it. The data set was
1889
02:31:35.569 --> 02:31:41.309
too small. The HL-LHC will produce enough Higgs pair events,
1890
02:31:42.110 --> 02:31:45.530
rare one in thousands of Higgs decays leading to a
1891
02:31:45.590 --> 02:31:50.819
detectable pair, to pin down the self-coupling with real precision.
1892
02:31:51.680 --> 02:31:54.920
What comes back from that measurement will either confirm the
1893
02:31:54.979 --> 02:32:01.069
standard model's prediction or contradict it. Both outcomes matter. A
1894
02:32:01.149 --> 02:32:05.389
contradiction would be the most significant result in particle physics
1895
02:32:05.450 --> 02:32:10.110
in decades. The Higgs decay into muons is a similar case.
1896
02:32:10.829 --> 02:32:15.340
One in 5,000 Higgs decays produces a muon pair. Run
1897
02:32:15.340 --> 02:32:19.930
3 found evidence of it. the HL-LHC will turn that
1898
02:32:20.030 --> 02:32:24.510
evidence into a precise measurement, testing whether the Higgs couples
1899
02:32:24.569 --> 02:32:29.950
to second-generation fermions exactly as the standard model says it should.
1900
02:32:30.770 --> 02:32:35.030
Any deviation, even a few percent off the predicted rate,
1901
02:32:35.579 --> 02:32:40.159
points toward new particles or forces operating behind the scenes.
1902
02:32:41.120 --> 02:32:45.809
The new precision timing detectors and upgraded silicon trackers being
1903
02:32:45.889 --> 02:32:50.909
installed during Long Shutdown 3 were designed specifically to catch
1904
02:32:50.969 --> 02:32:55.430
these rare events cleanly, stripping away the background noise that
1905
02:32:55.469 --> 02:33:00.090
made the measurement difficult before. Dark matter is the search
1906
02:33:00.149 --> 02:33:04.379
that may take longest. The LHC has already ruled out
1907
02:33:04.450 --> 02:33:10.889
the most popular theoretical candidates. certain supersymmetric particles that many
1908
02:33:10.969 --> 02:33:15.000
physicists expected to find in the first run. They were
1909
02:33:15.059 --> 02:33:20.319
not there. The HL-LHC will push into lower mass ranges,
1910
02:33:20.879 --> 02:33:25.459
testing models where dark matter is lighter and interacts through
1911
02:33:25.600 --> 02:33:31.010
mediator particles bridging the visible and dark sectors. If dark
1912
02:33:31.110 --> 02:33:35.190
matter is produced in collisions, it will leave through the
1913
02:33:35.229 --> 02:33:40.020
detector without triggering anything it shows up as missing energy.
1914
02:33:40.680 --> 02:33:45.280
With 10 times more collisions, the statistical picture of what
1915
02:33:45.420 --> 02:33:49.549
missing energy should look like under the standard model becomes
1916
02:33:49.690 --> 02:33:54.469
precise enough that a genuine dark matter signal would stand
1917
02:33:54.590 --> 02:33:58.850
out clearly against it. This is not guaranteed to work.
1918
02:33:59.469 --> 02:34:04.479
The dark matter candidate could fall outside the LHC's reach entirely.
1919
02:34:05.010 --> 02:34:07.850
but the search will be more thorough than anything that
1920
02:34:07.889 --> 02:34:11.809
has been attempted before, and ruling out more of the
1921
02:34:11.870 --> 02:34:17.000
parameter space is itself a result. What happens if several
1922
02:34:17.040 --> 02:34:21.479
of these measurements come back wrong at once, not one anomaly,
1923
02:34:21.940 --> 02:34:26.100
but three or four, each pointing away from the standard
1924
02:34:26.180 --> 02:34:31.809
model in different directions? That is the scenario that rewrites physics.
1925
02:34:32.489 --> 02:34:37.469
A single confirmed deviation at 5 sigma is a discovery.
1926
02:34:38.270 --> 02:34:43.239
Multiple confirmed deviations would be a framework problem. They would
1927
02:34:43.280 --> 02:34:47.540
suggest that the standard model, successful as it is, is
1928
02:34:47.579 --> 02:34:53.079
a low-energy approximation of something deeper. The theoretical candidates are
1929
02:34:53.120 --> 02:35:01.850
already waiting. Supersymmetry, extradimensions, new gauge symmetries, leptoquarks. None of
1930
02:35:01.909 --> 02:35:07.739
them are confirmed. Each predicts specific signatures that the HL-LHC
1931
02:35:07.799 --> 02:35:11.659
could detect if they are real. What follows a genuine
1932
02:35:11.719 --> 02:35:15.500
discovery of new physics is not just a new particle
1933
02:35:15.620 --> 02:35:18.959
added to the table, it is a new generation of
1934
02:35:19.040 --> 02:35:24.719
experiments designed around whatever the new theory predicts. New colliders.
1935
02:35:25.379 --> 02:35:32.540
New detectors. New questions asked at higher energies. probing shorter distances,
1936
02:35:33.139 --> 02:35:37.340
looking for the next layer down. And if the HL-LHC
1937
02:35:37.440 --> 02:35:43.500
finds nothing? If every anomaly fades, every measurement lands exactly
1938
02:35:43.540 --> 02:35:47.420
where the standard model said it would? That outcome has
1939
02:35:47.520 --> 02:35:51.229
its own weight. It would mean the theory survives at
1940
02:35:51.309 --> 02:35:56.129
energies ten times more precisely probed than before. It would
1941
02:35:56.209 --> 02:36:00.129
push the scale of new physics higher. making it harder
1942
02:36:00.170 --> 02:36:04.409
to reach experimentally. It would sharpen the question of what
1943
02:36:04.530 --> 02:36:08.850
kind of collider comes after this one. The conversation about
1944
02:36:08.930 --> 02:36:13.700
a future circular collider, a machine with a circumference nearly
1945
02:36:13.899 --> 02:36:18.719
four times larger than the LHC, reaching energies of 100
1946
02:36:18.719 --> 02:36:25.190
tera-electron volts, is already underway at CERN. That proposal exists
1947
02:36:25.309 --> 02:36:30.870
because physicists understand that if the HL-LHC does not crack
1948
02:36:30.930 --> 02:36:34.629
the standard model open, the next machine will need to
1949
02:36:34.709 --> 02:36:39.270
hit harder. The questions are on the table. The machine
1950
02:36:39.329 --> 02:36:43.069
is being rebuilt to answer them. And somewhere in the
1951
02:36:43.129 --> 02:36:46.329
data that will come out of the next decade, the
1952
02:36:46.409 --> 02:36:49.670
rules of reality are going to look either more familiar
1953
02:36:50.190 --> 02:36:53.930
or completely different. And there is no way to know
1954
02:36:54.030 --> 02:36:56.389
which until the collisions begin.