Beyond the Higgs: What's Next for the LHC? - with Harry Cliff

Well, thanks Martin, very generous introduction, that's very kind of you, so it was actually almost five and a half years ago when CERN announced to the world that they discovered

what

they cautiously described at the time as a new boson that we have now classified . A pretty safe conclusion is at least one Higgs boson, and around that time, suddenly, particle physics was all over the news. Brian Cox was brought around the TV studios to explain to the TV presenters who looked a little bewildered

what

spontaneous symmetry breaking was, and suddenly everyone started talking. They moved on with their lives and forgot about us and you could be forgiven for thinking that we actually set foot in CERN and just had a holiday for the last five years because it really hasn't been another breakthrough, at least not one whatever appeared in the news, so what I want to talk to you about today is what we have actually been doing and particularly there is something quite right, it's true, there hasn't been a breakthrough yet, but only in the last year or two.

There have been some really intriguing signs that we might be and, being very cautious about it, we might be on the verge of discovering something really quite profound, so this is CERN, which is the European Organization for Nuclear Research just outside of Geneva. , is the size of a lot. The population of a small town at CERN at any given time is about two and a half thousand people, about seven thousand physicists from all over the world who are involved in research there, and it has everything that a small town should have: it has a restaurant, it has a Post office, travel agents, it has hotels, it's a kind of city populated exclusively by particle physicists.

You can imagine what it must be like. This was the scene in CERN's main auditorium on July 4, 2012. Now this is so exciting. As you'll always see with particle physicists, they were clapping and cheering, you know, people punching the air. One of the people in the crowd described it as if it had been a football game. I'm not sure she's ever attended a football game. but I mean it was certainly very lively by the standards of physics and this is what everyone was applauding like a punch, so physicists get very excited about punches, this is if you want to know what the Higgs boson looks like , this is basically what the Higgs boson looks like.

It looks like a bump on a chart, so I'll explain what this shows a little later in the lecture, but actually what you're looking for here is this descending shake line and then there's this tiny little XS here and that was the smoking gun. which tells us that a new particle had been found that in recent years has been confirmed almost certainly to be the Higgs boson that Peter Higgs predicted in 1964, so what is a Higgs boson? You might ask, and that's very reasonable. question, so I'm going to take you very briefly on a quick tour of particle physics to try to understand what this actually is, so let's start with something a little more familiar: this is the periodic table of chemical elements that dates back to the 20th century.

XIX, so at the end of the 19th century the theory of what the universe is made of is understood quite well. There are over a hundred different chemical elements known and thanks to Dalton's atomic theory, that's what he said it was for each element, hydrogen, helium, lithium, etc., there was an atom that was a fundamental little thing, indivisible and indestructible, and you had different atoms, one for each element, so that was a kind of Victorian view of the nature of matter, so here's your atom. At the beginning of the 20th century, in 1897, actually, the history of Canada where I work.

I knew that a particle was discovered. The first elementary particle we found was called the electron and that led in the following years to a revision of the structure of atoms. Atoms, as I said before, were thought to be something hard, indestructible and indivisible when the electron was discovered, that was revised and we got the model of the atom that we all learn in school, which is a nucleus that contains most of the mass of the atom and that is positively charged and around the atom go these electrons, now the periodic table, if we look at the way the elements were organized, there are certain patterns in the properties of the different chemical elements, for example, if We looked at group one, all the elements tend to react in a similar way and become more reactive as you go down, but there are clear patterns in the way the elements are organized and that was kind of indicative of some more structure. deep and this is the deepest. structure, so you can essentially explain the properties of all these different elements by different numbers of electrons running around the outside of the atoms, and the electrons are what determine the chemical properties of that particular element.

Now this is not the end of the story, so if you zoom in. In the nucleus it was discovered around the 1930s that the nucleus itself is made of smaller things and these are called protons and neutrons, so they are smaller particles that make up most of the mass of the atom. The proton is positively charged. The neutron is electrically neutral, they are much heavier than electrons, they are approximately two thousand times more massive than electrons. This may possibly be where school physics ended, but in the 1960s, if you discovered that actually protons and neutrons are not fundamental, they are made of even smaller things and we call those smaller things quarks, quarks. , depending on your taste, so the proton is made of two up quarks, which are these red triangles, and one down quark, and the neutron is made of two down quarks. and an up quark and that's it, which basically says that all matter, every atom in the universe, everything we know is actually made up of just three different elementary particles, so we have the electron first discovered by JJ Thompson at Cambridge in 1897 you have and the two quarks, the up quark and the down quark, so everything that exists is made of just these three things, so it's just quarks and electrons organized essentially in a rather peculiar way and these are the first three particles of what we now call the standard model standard model of particle physics is a pretty boring name for something quite extraordinary it's really the closest thing we have to a complete description of the universe at the fundamental level the only good thing it actually leaves out quite a bit things, but The main thing that you might be familiar with that it doesn't include is gravity, but other than that, it's got it pretty well fixed, so you have these three particles that make up all the matter that we're made of, so there's something. another thing that is added to this table called neutrino neutrinos are a kind of ghosts they are these invisible and almost undetectable particles there are billions of them passing through you at this moment they are produced by the Sun in large quantities that go directly through you through Earth and very, very rarely interact with the ordinary matter that we are made of, which is why we are not so aware of the existence of neutrinos most of the time, so this column of four particles constitutes what we now call the first generation of matter, for some reason that we do not understand, nature provided us with two additional copies of these particles, there is something called second generation and in the second generation all the particles are exactly the same as in the first generation, except that they are more massive and unstable, so for example the electron has a kind of heavy cousin called a muon, which is about 200 times more massive than the electron and the reason we don't have it is that we are not made of muons and we are not There are muons going around it is because if you create a muon it will decay very quickly into an electron and some neutrinos, so these second generation particles don't stick around very long, they are unstable, but you can create them in high-energy collisions like in the LHC for example and then to start another one and then there is a third generation that is even heavier, so this is what these four by three twelve particles are the particles of matter, so they form the type of solid matter of the universe essentially or at least they would be if they weren't all unstable apart from this first column and we don't know, it's a big mystery, we don't know why there are two extra columns in this table, it's a bit like the periodic table in a way where you have this kind of structure and you can see these patterns, but you don't really understand yet in the 19th century what underlies this, but there is something suggestive here, something that suggests that maybe there is some deeper structure that could explain why we have this rather peculiar set of matter particles and I'll come back to that in a moment and then the last ingredient of the standard model is the force particles, so there are three fundamental forces in the standard model.

The model probably most familiar to you and on which a lot of important work was done in this building is electromagnetism, so Faraday and Maxwell and several others, that is the force that makes electrons stick to the nuclei of atoms, join the atoms. responsible for chemistry is responsible basically for most of the things that are important to us and the particle that transmits the electromagnetic interaction is the photon, the particle of light, so light itself is also an electromagnetic phenomenon, then there is two or three more particles that You may not have heard of that there is something called a gluon, which is the force particle of something called the strong nuclear force, which is a force that binds the quarks together within the atomic nucleus and binds the protons together. and neutrons.

It's called glue because it essentially holds things together. and then there are two quite strange ones called w and z particles and these are particles that transmit a third force and an even stranger one called the weak nuclear force. Now, the weak nuclear force doesn't really bind things together like electromagnetism or the strong force. The force is responsible for causing particles to decay, so when a muon turns into an electron, that happens through the weak force. I'll talk a little more about the weak force. The weak force is very important, although we do not really notice it in our daily lives.

If it were not there, the Sun would not be able to fuse hydrogen into helium and there would be no matter in the universe, so it is very important, although it is not something with which we are very familiar, so this is the standard model. and this was the standard model as it had been studied and observed on July 3, 2012 and on July 3, 2012 there was a missing piece which was the Higgs, so what is this Higgs boson and why is it so important? Well, to understand that we actually need to ask a little deeper question, which is what do I really mean by particle so that they can be forgiven.

I kind of did the way I described this to you in the last few minutes, you might get the idea that maybe these particles are somehow like little Lego bricks or are a little bit like Victorian atoms; They're sort of like little solid points that move and stick together, but that's not really what modern particle physics tells us that particles are actually particles. are not really what matters at all, is that our field has a somewhat bad name in the sense that we actually consider them to be fundamental particles or not, but fields, so it is a field that we probably all have if you have ever held a magnet

next

to it.

In a piece of steel or iron, you have felt the effect of a field, so a field is something that causes, for example, a force to be exerted at a distance where there is nothing physical to actually cause that force to be exerted. , so you have something that I feel like it might be safe for the guy a magnetic field and that could be a strong magnet and it gets weaker as you get further away or it could be a gravitational field like the one the Earth creates around it or the Sun creates around there, so we think that actually, in particle physics, each of these particles has a field associated with it, so there is a field for quarks, electrons, neutrinos and for all the force particles, and the way we think about these particles is actually so small. waves moving through these fields, so this is a pretty nice cartoon, but my colleagues at Cambridge, David Tong, is a theoretical physicist, so here you have your fields as a sort of blue sheet and then here you have some particles that have an impact.

So they're kind of little localized perturbations in these fields and that's how we think of all matter, so the electrons, the quarks, everything is just little waves that move through these cosmic energy fields that fill all of space, They're everywhere, which is a pretty strange idea. but that's really how we think things are going back to the Higgs, what is the Higgs? Well, the problem existed in the 1960s, whenWhen the Standard Model was being put together, it was discovered that if you tried to make the particles in the Standard Model massive, then the theory fell apart, it gives you nonsense answers, so in particular there was a particular problem with these W and Z particles. , these particles that transmit the weak nuclear force, it was known that if they existed they had to be extremely massive, but if you gave them mass in the theory, the theory gave you meaningless answers, so there had to be some solution to this and the solution was to essentially invent another field, just like the other fields, that these particles are waves that move, well, Peter Higgs essentially said and actually five other colleagues that he was working with at about the same time imagine that there are in everything The entire universe has an additional cosmic quantum field and as these massive particles, these things that we think are massive move through it, they are actually imbued with mass by this field, so, for example, the electron that has a certain mass, what the Higgs mechanism says, is actually the The electron has less mass, but by interacting with this cosmic energy field it acquires the property of mass, which is why Higgs wrote a paper in early 1964 and he had this idea that was written in very fancy mathematics that looks a little like this and don't worry, I won't try to explain what this means and he sent it to the magazine and it was rejected.

They basically said this has nothing to do with physics, so Peter Higgs has good math, but you don't know anything to do with reality, so Peter Higgs went back to his paper and said, well, I need to connect this to something that can be measured. experimentally and what he added to his paper was basically a line that said if this cosmic energy field that gives mass to all particles exists, then you should be able to create a wave or a disturbance in them that would show up as a new particle and that The thing that ripples in the Higgs field is what we call the Higgs boson, so that's what gives them all mass.

The most important thing of all for the particles that we form is at least this field and the Higgs really is the proof that this field exists and that is why finding it was so important because the Higgs mechanism, this Higgs process by which the particles gain mass, it is absolutely fundamental. For the standard model, it's like the keystone of an arch, if you take it away, the whole theory just falls on itself, so it was absolute. People were almost convinced that this thing must actually be out there and that's why they found it. was so crucial and what everyone was so excited about on that 4th of July, so with the discovery of the Higgs this completes this standard model of particle physics that I've been talking about and this theory is really incredible. achievement actually because we can, it can be used to explain practically all the physics that we can see around us, so you can use this animal in principle to describe everything from you know why a light bulb produces photons to how atoms fuse in its interior. stars, it is the closest thing we have, as I said, to a theory of everything and to give you an idea of ​​the power, the predictive power of this theory and this is, in reality, as I am going to tell you now, it is the best scientific prediction anywhere in the world. science as far as I know, so here's the electron, now the electron, in addition to having an electric charge, it also behaves a little bit like it's a little bar magnet, so it has a north pole and a south pole and it emits a magnetic field and you can use it. the standard model for calculating how strong the electrons in the little bar magnet should be and you can do this with absolutely fantastic precision, so essentially what you do is you use a supercomputer, you put the theory into the computer, you calculate and you get a number which looks like this one one five nine six five two one eight zero seven point three plus one is two point eight times ten to the power of negative thirteen there is a very small number but calculated very precisely with a very small uncertainty this is your theoretical prediction now If you do In a very, very clever experiment, you can measure this quantity, a very small quantity, two, very high precision and this is what you get: one one five nine six five two one eight one seven point eight or so seven point six, so you can see these numbers.

I agree even to the last type of three significant figures and the difference between this number and this number is within the experimental uncertainty in this measurement, so this is a prediction and a measurement with an accuracy of one part in a billion which is really extraordinary. That tells you that this standard model is definitely on to something. I mean, you don't get this kind of result by accident, so it's a really successful theory, but it's not without some problems and these problems are actually what partly motivated the construction of the Large Collider in the first place. of Hadrons, as well as the discovery of the Higgs, which was really kind of the closing chapter of 20th century physics, what everyone was looking for, well, a lot of people were looking for answers to some big unsolved questions. that the standard model cannot address now.

I'll come back to this image, so it's actually an image taken by the Hubble Space Telescope. It's called the Hubble Ultra Deep Field and what it essentially is is where the telescope is pointed at a very dark place. portion of sky where there are almost no stars and if you wait a long time and wait longer for extremely faint light to accumulate on the telescope sensor and finally this is the image you get so what you can see In this image in There are actually some stars there, things with cross-scintillation patterns, but everything else is pretty much a galaxy.

These are extremely distant galaxies, almost to the edge of what we can see with telescopes. Well, for example, in the center of the image you can see that there is a kind of galaxy cluster, these types of spots. Now, hopefully, you should also be able to see that in this image there is a pattern of spots, so there are sort of circular structures arranged around it. this central cluster of galaxies now what this speck is is something called gravitational lensing, so it's essentially where light from distant galaxies travels towards the earth. Now thanks to Einstein we know that gravity not only causes matter to move in orbits or curves, but also to curve. space-time and it will make light travel in curved paths so what's really happening is imagine you have your yes you yes me yes mike yes I'm a galaxy is here and the earth is there and there's something heavy between me, well , also galaxy and the Earth there, when the light leaves the galaxy and passes through this heavy object, its gravity bends it and pulls it towards the Earth again and what you end up getting basically acts like a lens and you end up getting this type of image multiple spotting of the same galaxy all over the sky and therefore this lensing effect can be used to calculate how much matter is in the center of this image because the more gravity, the more mass there is here, the stronger the lensing.

The light will be and the more pronounced this effect will be, so what you can do is if you use this lens, you can calculate how much mass there is actually in the center of this image and then you can compare that to the visible light that you can see, then we can see that there are a lot of galaxies here, obviously there is a lot of mass and what you really find is that there is a very large discrepancy between the amount of things that you can see with your optical telescopes and the amount of things that we know must be there to explain this lensing effect and if you overlay a map of where the matter appears to be in this image from the lens, this is what you get, you get this kind of bluish purple cloud, this is evidence of something called dark matter, which is essentially a kind of invisible substance that we don't know what it is, that apparently makes up a very large fraction of the universe, in fact, it's much more abundant than the atomic matter that the standard model basically describes, I mean. this dark matter actually, so you have evidence of dark matter from lenses, you also have evidence of dark matter from simulations like this that show how the universe formed in the early stages and essentially you find that if you want to show how it formed the structure in the universe You need dark matter, if you don't put dark matter in your simulations then you won't get a universe that looks like the one we live in.

This is from the illustrious simulation group. It was quite lovely, anyway, you can see galaxies exploding. Life and stars revolve around very beautiful things, but dark matter is needed for this to work and be in accordance with what we see in the sky and through these types of techniques through lenses and also by observing the rotations of stars around galaxies. We can calculate with a fairly high degree of confidence how much dark matter is out there even though we can't see it and this is what you get, this is our cosmic pie and essentially what you see quite extraordinary is this slice here that has labeled atoms that we are basically us and everything we can see when we look at the sky, so all the galaxies, stars and planets in the universe and everything that the standard model describes are only 5% of the total content of the universe, 27% of that is , more than five times as much of the universe is made of this invisible dark matter and we don't know what that is and then 68% is something called dark energy and we don't really know what that is, so dark energy is some kind of repulsive force mysterious thing that seems to be causing the universe to expand at an ever-increasing rate, so the lesson of this is essentially that when you hear the word darkness in physics you should be very suspicious because it basically means that we don't know. what we're talking about and this is really extraordinary in the sense that you've built up what appears to be an amazingly successful theory for a century with all these clever experiments and theories and then you realize that what you've been describing is actually only a small fraction of the total content of the universe, so in this extraordinary position of having a theory that works very, very, very well in the narrow domain in which we have applied it but that basically tells us nothing about the ninety-five percent of what it is. out there, so it's definitely a small omission.

I guess you could say that in the standard model there are other problems as well, so we don't know what ninety-five percent in the universe is quite large, another has to do with something called antimatter, so in that table I showed you the beginning With all the particles of matter, the quarks, the electrons and their cousins ​​and the neutrinos, for each of these particles there is a kind of mirror image particle and this has actually been known for a long time. It was discovered a long time ago in the 1990s. 1930, predicted by someone named Paul Dirac and then discovered in experiments very soon after.

Each particle in this table has a mirror image where all the properties are exactly the same but the electric charge is the same. the other way around, for example, the electron that has a negative charge has a positively charged version called a positron or anti electron, depending on what you prefer, and there are your muons, anti muon, there is the up quark and the ante up quark, the down quark , the anti down. quark and so on, and these are also part of the standard model, we know that these things exist, they can be created very reliably in experiments, their properties are studied and we know that they are out there and we also know that they are actually indistinguishable from the Las matter particles, except their charges are the other way around, now this is a little problematic because if you naively apply this kind of understanding of matter and antimatter to the formation of the universe, then this is what happens, so in the Big Bang you have a huge amount of energy and that energy is converted into matter and antimatter and in the standard model every time you make a matter particle you also have to make the corresponding antimatter particle, so if you make an electron you also make it the positron and there is this.

They called me a kind of maelstrom, all these antiparticle particles are being created and at the same time as they are created, they also collide with each other and annihilate and become light, so this exchange between energy, matter and antimatter is boiling and boiling. and eventually what happens is that the universe expands enough to cool down enough for all the matter/antimatter to annihilate and you turn on what you're left with is a cold, dark, lifeless universe with a few photons whizzing through. of infinity. darkness this is what the standard model says the universe should look like this is what the universe looks like so copyright Lucasfilm so the existence of the staff and us and the galaxies is a little inconvenient if you're a theorist because yes, we can't really understand that, so there must be some kind of process by which a little more matter can be allowed to survive this cosmic annihilation at the beginning of the universe and actually beyou can calculate how big that imbalance must be. it just has to be very, very small if you look at the sky and essentially count the number of photons whizzing through space, there's a rough correspondence between how many photons are out there and how many antiparticles our Nile ate at first because each annihilation more or less creates two photons, there are about a billion photons for every atom in the universe and what that tells us we really are, we are one billionth of a much larger amount of things than there were at the beginning, but we don't know how it survived.

This billionth part, should not be there by rights, everything should have been annihilated and we should not be here, so those are two big problems: the fact that we do not know that 95% of the universe is and also the theory tells us that the universe should not exist, so two big problems, I will address a third and this is one that has probably motivated many theoretical physicists, particularly almost since the war, since Einstein really in the 20s and 30s, so This It is a problem that has to do with gravity. Now it turns out that gravity, although it feels quite strong, sticks us to the ground.

If you fall out of a window, it hurts quite a bit. In reality, it is terribly weak. It's a fantastically weak force and this cartoon illustrates it. period, so we have the Earth, which is nice but pretty big by any standard view and it has a gravitational pull and it's pulling on this clip. I can use a very weak refrigerator magnet that's only this big to lift that paper clip so that the magnet overcomes the gravitational pull of this huge ball of rock, you know, many, many. many times more you know bigger in terms of mass, which essentially tells us that the electromagnetic force is much stronger than gravity.

If you had a magnet the size of the Earth, it would be fantastically powerful. You can compare these two, so if we say that electromagnetism has a force of 1, then the force of gravity is 10 to the power of negative 36 or so. I won't read that and this is a real conundrum. Why is there such a great hierarchy between gravity and other forces? strong, weak and electromagnetism are much stronger than gravity and we don't understand why that is so there are a lot of problems potentially, they are not very big problems and that is largely what the LHC was built for.

Try to figure it out, luckily, although there are a few possible theories that could explain some of these and one of the most popular is an idea called supersymmetry. Now supersymmetry, the essential idea is to invoke a new type of symmetry in nature and it is a rather strange symmetry. symmetry, so it's not really like this mirror image of antimatter, but it's somewhat comparable. I guess in supersymmetry there is a symmetry between matter particles, so they are things like quarks, electrons, neutrinos and force particles, which are the gluons, photons and weak particles and the Higgs as well. and in supersymmetry every matter particle has an associated force particle and every force particle has an associated matter particle, so you end up with an extra table of particles that looks like this, they all have really stupid names, so basically , if you want to know what particle name is in supersymmetry, you add an S in front so that the electron becomes this electron, the muon becomes this mule.

I think the worst of all is possibly the strange quark, anyway there should be some kind of commission to name things. I don't know how this happens. They are called sparticles. It sounds very silly. The way I've described it is very clever as supersymmetry, although I don't, but supersymmetry actually is. I mean it's kind of the interest in supersymmetry that started in the '80s and it's been the most popular extension of the Standard Model for a long time and that's because it's incredibly good at solving some of these problems that I described to you in terms of dark in particular, so one of the reasons supersymmetry is very popular among particle physicists is that often the lighter particles are stable and often they are also electrically neutral and that is exactly what is wanted for matter dark, so I said dark matter is invisible and that's because it doesn't reflect, absorb or emit light, and things that don't emit, absorb or reflect lights are electrically neutral, so you have an electrically neutral particle that doesn't It interacts with photons and could well form dark matter in the universe, so that's a There's a kind of obsession in physics that is trying to unify things to simplify complicated phenomena into a single underlying type of phenomenon and that's true with forces. in particular and unifying the different forces in physics has been sort of There are also searches going on since Maxwell unified electricity and magnetism in his equations in the 19th century, so this is a pretty confusing graph, unfortunately not always I produced this way, but it's backwards, but basically what you have here is this axis. is the strength of the three different forces in the standard model, except they get stronger as you go down instead of up, but that worries me too much now, if you do experiments and measure the strength of these forces, what you find, interestingly enough, is that the strength of the forces changes as you get more and more in energy, which basically means that if you have a collider and you hit particles together, the harder you hit them together, the forces, the Lee forces become essentially alter and what As you see in the standard model, if you do experiments with higher and higher energies and these are much higher energies than we can actually produce in an experiment, but this is done with theoretical calculations, you will find that on a scale very, very high energy, there is a point where these three lines (the electromagnetic force, the weak force and the strong force) come together a little, but not completely.

If supersymmetry is introduced, these lines meet exactly at a particular place called unification and this suggests that with supersymmetry these three forces are unified into a single superimposed force which should possibly be called a force and that is another reason for us to like it supersymmetry, unifies these three seemingly disparate forces into one, in fact we have already unified these two, that is partly what the Higgs is involved in, but it doesn't matter, rather it is just a strong force, the other reason why the one we like supersymmetry is that we now double the number of fundamental particles to discover, so people like me remain employed for a long time, that's good, so we like supersymmetry, another possible This theory tries to explain the weakness of the gravity.

There are several different versions of this. Basically, these theories posit an extra dimension of space or sometimes more than one extra dimension of space as a way to explain the weakness of gravity now. apparently this is a picture of what the extra dimensions look like. I mean, okay, I'm not so sure, but yeah, apparently it is anyway. Basically what's the idea: there are some extra directions you can move in, then up and down, left and right and forward and back and the reason we don't observe them is because the particles we are made of are a kind of three dimensional space-time and only certain things can travel through these high dimensions or is it because these extra dimensions are very small and therefore impossible to observe and the way to explain the weakness of gravity generally is that gravity leaks into these extra dimensions so that gravity can move through all the dimensions of space and therefore dilute itself, while electromagnetism is restricted to living within these three dimensions that we are with familiar and if you want to know the results of having extradimensional theories like this, this is what an extradimensional theory looks like according to the Daily Express, so it creates a black hole at CERN and swallows the whole world, so we haven't seen it yet , actually this is what they really look like, so if you do basically extradimensional theories, you can often create little black holes, so this is where they collide. your particles with enough energy actually collapse a small region of spacetime for a small moment into a black hole and the reason we're not really worried about these black holes eating the earth like in that rather silly animation is, according to Hawking.

In theory, these black holes should evaporate almost immediately, so as soon as they are created, just and this is a simulation of one of these black holes disintegrating, so the black hole was here and it turned into a whole bunch of other black holes. particles and they give a very signature characteristic feeling in your detector if you manage to do one of these things and it's not the whole world falling into a hole, then finding the Higgs was a goal, but finding all these things was a big part of the reason for which the LHC was built and Now I will take you on a brief tour of this truly extraordinary Sheen.

This is a map of Europe. Let's get closer to Switzerland. This is Lake Geneva. Geneva is right down here and rising up, so we'll get a little closer. It's an aerial shot from a plane of the Geneva area, so again you can see Lake Geneva. The city of Geneva is a kind of gray blur. This long thing here is the airport runway that turns there and they are marked in yellow on the field. the route of the Large Hadron Collider, so this is the largest scientific instrument ever built by the human race, by some measures, it is the largest machine they have ever built it is 27 kilometers in circumference, it crosses the Swiss-French border twice, actually this yellow line is not there, in real life, it is about 100 meters underground, the main reason why it is underground is actually not because it is dangerous and somehow it emits a lot of radiation from the that you have to protect yourself, but because it would be very expensive to buy 27 kilometers of land to build it so that it is just below the surface and the way it works is really quite simple and quite brutal.

Here at CERN there is a hydrogen gas bottle of this size that is connected to a 30 meter long particle accelerator and hydrogen is taken. out of its container it is hit with an electric field the Hydra atoms are destroyed the electrons are torn from the hydrogen atoms and you are left with protons that are just the nuclei of the hydrogen atoms and those are sent by an accelerator and are sent through a series of accelerators at CERN, so imagine kind of buzzing around several different loops, eventually entering this ring called the proton super synchrotron, which in the '80s was the largest particle accelerator in the world, but now it's just a feeder for the much larger Large Hadron Collider, so it has a beam of protons that goes one this way, one this way, and then four points around the ring.

These protons collide inside Antek's three-dimensional digital cameras that take photographs. essentially from these collisions and try to see if we have created new particles, so if you go underground, this is what you see, a very, very long blue tube that curves in the distance that people use, there are about eight wells of access that take you down. In the tunnel, people use bicycles to get around because the distances are very long, so this blue tube is essentially the largest thermos in the world. Inside there is a bath of liquid helium at -271 degrees Celsius, so it is just above the tube, a little less. more than two degrees, absolute zero, the lowest possible temperature and the reason it is very cold is because the way these particles are directed around the ring uses incredibly powerful magnets and these magnets are superconducting, which means that They have no electrical resistance and that means they can create extremely strong magnetic fields, but they only work at very, very low temperatures, so the whole machine is cooled by liquid helium pumped intravenously through this whole ring, so do that the magnets work.

The engineering challenges in building this are also absolutely extraordinary. One fact that I found surprising when I learned it is that you probably learned, maybe you remember it from school, if you take a piece of metal and you cool it, it gets a little smaller, it contracts slightly, so you're getting cooling. a 27 kilometer long piece of metal basically at 271 degrees and what happens when you do that is the whole machine shrinks by 30 meters in length, so this thing that has to be aligned at a micron level has to able to contract. for 30 meters without breaking and without misalignment without going wrong and the fact that it works is really amazing.

These are the other parts of the machines. You have a very, very long blue tube and then in four places around the ring this tunnel opens out intothese. huge underground caverns the size of a cathedral and inside these caverns are extraordinary looking machines like this, this is the compact muon solenoid, which is a strange use of the word compact, so this thing is 15 meters tall, so There's a guy with a climbing helmet. there it's 20 25 meters long it weighs 12,000 tons it contains enough iron to make two Eiffel Towers essentially what this thing is is an incredibly sophisticated gigantic 3D digital camera so what happens is the particles that the protons enter through this beam tube and in one for the In another direction, this thing is barrel shaped, so imagine it goes off the edge of the image, they collide in the center, you get a lot of things moving everywhere and this detector records those collisions in real time, actually 40 million times a second, this is the This is another one of these There are four of these things This is the biggest of them all This is Atlas, which is a pretty cool sounding name, it's a Bit of a tortured acronym, so I won't try to tell you what it is. actually means, but essentially Atlas is even bigger than CMS, this thing is 25 meters high and 40 meters long, it's absolutely huge if you ever get the chance to go to CERN and go underground to see these things, I would which I think is quite difficult unfortunately nowadays. because there's a lot of activity there, I mean, when I saw them a few years ago, they really are the most amazing things you've ever seen, amazing, so Atlas essentially does a very similar job to the CMS.

They are two different experiments, but they work in print, they work with similar principles but they have completely independent equipment and technologies and they are really there to verify the results of each other, so this is a representative image of what happens when two particles collide. It's actually a real picture, so this is what they do. I have the date, I think it says June 25, 2011 at 6:30 in the morning. This has two protons that meet. What happens. The reason we're doing these collision experiments is what we're actually doing. We often hear particle accelerators or colliders described as atom colliders and that suggests that what we are doing is smashing atoms to see what's inside them, but that's not really what we're interested in.

People have known what is inside atoms for quite some time. What particle colliders actually are. They are ways of producing matter that normally does not exist. the universe, so you carry a large amount of energy in each proton, they are given enormous speeds, they go at 99.999999, 1% of the speed of light, when they collide at this point, they carry 7000 times the energy of its mass at rest as kinetic. energy, that means you can make something that is essentially 14,000 times heavier than a proton. In the collision, they come together, the energy, their kinetic energy becomes matter and that's what you're seeing, so you're seeing hundreds of particles being created and These are not things that come from inside the proton, well, in some cases are, but a lot of them are things that are essentially made from this kinetic energy.

This happens, this process of collisions happens forty million times a second within the four. experiments and run for most of the year, usually from April until just before Christmas, so 24 hours a day, with occasional technical stops so you can get an idea of ​​how many of these collisions occur, they are absolutely huge and the data The challenges of dealing with this rate of collisions are also really extraordinary, so I'll try to briefly explain to you what that bump was on that graph that I showed you at the beginning, so how do you find a Higgs boson?

Well, two protons collide. and if you're really lucky, they'll create a Higgs particle. Now the Higgs particle only lives for a small fraction of a second. I think it's about 10 seconds minus 24, so it's too short to be detected, the Higgs is not. It never reaches the detector, it is simply created and instantly disintegrates. Now one of the ways it can decay is into two particles of light, so you get two high energy photons, two gamma rays flying out from the collision point that arose. this Higgs decay and this is what this event shows this is from Atlas again from 2011 so you can see these two big bars here there are two photons so what an analyst does a physicist will say well I'm looking for the Higgs so check everything these billions and billions of collisions and find me all the collisions in which two high energy photons were produced because they could have come from a Higgs boson and then you take the energy of those two photons, add them together and calculate what the mass of the object they came from, which was created right in the center of this collision, so you're reconstructing what the Higgs decayed into from the bits that you end up flying through your detector, it's a bit like blowing up a car and try to determine what kind of car it was from the bits of shrapnel that essentially flew by and what you then do is take all these pairs of photons, calculate the energy, the total energy, and plot it on a graph and that's it. , so just on the vertical axis you have the number of pairs of photons and on the horizontal axis you have the total mass of the object they would have come from now most of the time when you look at two photons, they didn't come from one Higgs, they came from another thing, so there are many ways to produce photons, if you hit protons really hard, you get light, that's what happens, so most of the time it's essentially just background noise and the reason.

The hit is important is a certain mass that is one hundred and twenty-five times more or less the mass of the proton. You can see this little excess and that's because every time you do a Higgs, the Higgs is always the same. A Higgs always has the same one. same mass, so the Higgs photons always add up to the same mass, so you get a little excess in that particular value, so this increase is the sign that this is really there and what really convinced everyone that day in July 2012, both Atlas and CMS experiments saw a bulge in the same place and that's what everyone stopped when everyone really got excited inside clapping, so that's cool, the LHC turned on for the first time with untapped success in 2009.

It ran for about two and a half years until the Higgs came along and the Higgs announcement came in July 2012 and everyone was very, very happy that day, but since then there has been kind of a series of bad news. 2011, in fact, even before the Higgs was found, said that certain results were really causing some problems for some of the other theories we were looking at, particularly supersymmetry, so when the LHC was first turned on there were some ideas that there were so many supersymmetric particles. so many particles that they couldn't handle them and now we won't be able to read the data fast enough.

Actually, what's happened is that there hasn't been any sign of these things, so there's one that tells us 11, that is. another one from the 2015 LHC still has bruises, supersymmetry is hard to kill, popular physical theory is running out of hiding places, so you get the idea, and this is, honestly, the story of the last 400, four and a half years, Five years since the Higgs was discovered, we've done it, there's been a lot of very important physics done there, I got it wrong, so, for example, one of the things that Alice and CMS have been doing is studying the Higgs and really trying to figure it out. identify it is This thing really is the Standard Model Higgs boson that Peter Higgs said should be there or it's some other kind of potentially more exotic thing, so maybe it's a supersymmetric Higgs boson, for example, but all those measurements They seem to say that it actually looked very similar. the Standard Model Higgs boson and all these other theories of the extra dimension of supersymmetry so far there's been no sign of them and I think people have honestly been getting a little anxious about this.

There was a big moment of excitement in 2016. It's the summer of 2016, a new lump appeared. I told you that physicists like lumps, so this is a very similar diagram to the one I just showed you. Again it's adding pairs of photons from the inside, in this case within the Atlas experiment and what they saw. Again there was something that maybe looked a little bit like a lump and this time it had a much larger mass, so the mass of the Higgs was about 125 protons or so. This thing had about 750 protons, so it was much heavier and this created a lot of excitement at the time.

It was possibly a little premature, so you have to be very careful with an experimenter and, in general, physicists. They are very cautious when they see something like this because there is a certain possibility that this type of hit could simply be a fluctuation, sometimes it is just by chance that a few more pairs of photons can be produced with that mass and that is a bit like pulling a die and you can occasionally roll ten sixes in a row, even if that's very unlikely if you do enough experiments, you'll get that kind of result from time to time, so maybe this was just a statistical fluctuation, but people got really excited.

This showed. This is a graph showing the enthusiasm of physicists. This result was announced around. on December 15, 2015 and this is the number of articles placed in the archive over the

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10 days, so you can see that on Christmas Eve alone there were almost 100 theoretical articles trying to explain what this little wobble on a graph was, like this There was a lot of excitement and I know that maybe it wasn't justified as it turned out that unfortunately it wasn't justified, so when Atlas produced the result again with more data, what they found was that this little movement had disappeared and essentially It was what it seems like.

No one who was lost ever made a mistake, it wasn't that the experiment was wrong, it's just that sometimes, you know, by luck or bad luck, sometimes you get a little fluctuation in your graph and that makes you briefly think that You've discovered something new, but you haven't actually, but I said something interesting was happening and it's actually a series of results that emerged from the experiment I work on and I can't claim to have been instrumental in these. I've done measurements myself, but it's been very exciting to be kind of an observer in all of this, so my experiment is called the Large Hadron Collider LHCb Beauty Experiment and beauty, well, beauty represents a particular type of particle, the be quark, which is actually generally known as the bottom quark, but we would rather be known as beauty physicists in lower physicists, so it's the Alexa V Beauty experiment, it's not as pretty as Allison CMS, it looks a little bit like a multicolored toast rack or something, but it's a very, very clever experiment, what LHCb does. is actually quite different from the other two big ones, Allison CMS, so generally speaking, what Alice and CMS do is what we call direct searches for new physics, that is, they want to attach protons, so here's a proton , another proton they give them.

A lot of energy crashes into each other and then you create a new, much heavier particle and you look at it like the Higgs, for example, and this kind of direct process, the mass of what you can create is limited by the amount of energy. you can put into collision, so if you remember, you know Einstein's equation e equals MC squared, which tells us that energy and matter are essentially interchangeable, so if you have energy e here in energy EE here, so the amount of mass you can make is We divide it by the speed of light squared so it tells you how heavy the object is that you can possibly create and that's one way of doing physics and that's how the Higgs was discovered and This is how much of the Dark Matter searches in all Supersymmetry searches work too.

What the LHCb does is a little different. It makes measurements that are generally indirect now as some kind of silly analogy. Everyone heard the joke: how do you know an elephant has been in your refrigerator? Footprints in the butter. Yes, exactly. If you like Atlas and CMS hunting elephants, going into the jungle with a shotgun and trying to find an elephant, don't do that and what HCB is actually doing is trying to find tracks left by elephants, so in a way they are there. They're kind of complementary in a sense, actually it could be quite a bit if there aren't many elephants in the jungle running through one, it could be pretty weird but if it leaves footprints all over the place you might be able to infer.

There's an elephant out there, although you might not know exactly what kind of elephant it is just by looking at its tracks, so that's the kind of analogy of what we're doing in terms of the actual physics, the B, like I said, means B. quark or bottom quark or beautii quark, so what we tend to study are the ways in which the peak path candecay, for example, this green spot represents a B quark and let's say it can decay into some other set of particles, about three more particles. which will decay now in the standard model, any decay process in which a particle becomes a group of particles usually occurs through the weak force, so this is the force that mediates these types of decay processes, so essentially this particle passes through the weak force into these three particles and just like you can use the standard model to very accurately predict the property of the electron, I showed you that a very long number at the beginning you can also use it to calculate how often the quark should be converted in the code. these particular sets of particles and you can count, rate the number frequently - a pretty high level of precision now, if there is some other force field, let's say there's a fifth force, let's just do it there, it could be supersymmetry, it could be something else If that force exists, it can very subtly influence the way these particles disintegrate; effectively provides another path from the initial state to the final state, so the standard model might be the strongest way to get from the quark to your set of particles it's decaying into, but its new physics can also provide a path and that will essentially slightly improve the disintegration rates of what type of game we play.

We measure these types of decay rates. How often does a B quark? become a set of particles and we compare that number with what the standard model tells us it should be and if that number doesn't agree, that may be an indirect clue that there is other matter of other particles, some other field of matter. force is coming in and helping that. it breaks down, so it says kind of precision physics instead of going out and hitting things together and looking for some big particle that you're creating, you're studying much more abundantly, these are still created in collisions, I mean, we're still hitting things. one of each other, but what happens with the B quark is that billions and billions of them are produced, so you can make very, very precise measurements and you can potentially detect these very subtle effects caused by new forces that lie beyond the uniform edge.

Beyond the energy that the collider can achieve, that is the advantage of indirect measurements, it is complementary to what Alice and CMS do now. What's been really interesting in recent years is evidence for something that sounds a bit arcane called lepton universality. This is essentially a property of the standard model, which is leptons, which are the electron, the muon, and the Tau, these three negatively charged particles, so each one is heavier than the other. Electrons, when we discovered 100 years ago, have a heavier version, the muon. an even heavier version called a towel and in the standard model these three particles are treated identically, that means that all forces interact with these three particles in more or less exactly the same way and that means that if you compare two processes involving electrons and muons, they should have exactly the same speed more or less than what we have had. looking at LHCb is this process, so you have to be your beauty quark and it decays through the weak force into a strange quark and two electrons, so that's the decay, it's from one particle to three and the two Electrons are the crucial and strange things to pay attention to.

Now, a test of this idea, a test of the universality of the lepton, the fact that the standard model treats all these different versions of the electron the same, tells us that if we look at the corresponding decay where the B quark becomes a strange cork and two muons which are the heavier versions of the electron, so the speed of this should be exactly the same and when people started thinking about this measurement there was no very good reason to think it was going to produce anything interesting it was kind of like it's good to test, the universality of leptons is kind of the principle of a standard model, so it's good to test these things just to make sure and what they found was that this is what the standard model says if Yes If you take the number of muon decays and divide by the number of electron decays, they should be equal, so what the standard model says is that the number more or less should be 1 - a fairly high level of accuracy at the LHC 2014. paper and this is what they measured so that's the uniform balance between the electrons of the eons they measured 0.75 plus or minus 0.1 so it seemed like there were fewer muon decays than of electron decays.

Now this is still not something to get terribly excited about, so if you look at the uncertainty, it is 0.1, this number is only 0.25 away from one, which means that you only need to talk about these fluctuations that can trick you into thinking that you found something new, it wouldn't take a very big fluctuation just to send. lower your number a bit and make it look like you've seen something new and interesting, so there was definitely interest in this. It's what we call a kind of 2 Sigma effect, which means it's two errors away from what you expect it to be. and a lot of papers were produced in 2014 as a result of this, then just this year the experiment produced an equivalent measurement, so it's with a slightly different set of particles but basically the same, comparing muons and electrons and this is what they measured. so they measure 0.68 or so point zero 8, so this is a little further away than you suspect and it's also very close to what was measured in 2014.

However, these are two independent measurements, so not They are using the same data. Using different data sets, the fact that they line up this way is quite intriguing and has caused some really serious interest, which is why these measurements are, at the moment, the largest deviations from the standard model in any experiment we have knowledge. And it's not just these, there are a few other measurements, as well as similar processes, that show slight discrepancies with the standard model, nothing independent yet to really be sure it's something new, but they all seem to line up consistently. and people are still criticizing you, rightly so, being very cautious because it could be that when these measurements are updated in a year or two they will again just be a statistical fluke or maybe we made a mistake, maybe we missed some systemic effect. in the experiment.

Hopefully that's not the case, but it's always possible, so it could be that these things disappear, but the other possibility is that it's not a statistical fluctuation, we haven't messed up, this is actually the sign of something really fundamental. new and the interesting thing is that it's something that no one really expected, it's not supersymmetry or big extra dimensions, it's something else and that in a way would be even more exciting because finding something that you really didn't expect is very often when the biggest breakthroughs happen. So what could this be? Well there aren't many, like I said, I showed you that graph with a hundred papers for that spike above, now there's something like 450 papers citing these two LHC results as a number of I'll also mention other results just one and that's because in part a that is a theory that some of my colleagues in the Cavendish lab have been talking about again very cautiously, so what is your line, it is extremely unlikely that this is a real effect because the standard model works very well If we're going to say that it's broken in some way that requires really extraordinary evidence, but if this is real, then it could tell us something really fundamental and it's a question that, in some ways, has been slightly ignored and we go back to this well, this image. again, this image of the standard model that we had at the beginning, so I said there are these three generations, the Quayle, going up in cooperative mode and going down the quark and the electron and then this charm and the strange quark and the muon, the quark upper and lower and the tower and I said, we don't know why there are three generations, we don't know why these items exist, well, one of the possible explanations for this discrepancy could explain this structure, so what could we be about to find some extension of the standard model that will be a bit like the discovery of the electron in the 19th century.

Explain this peculiar periodic table of particles that we currently have. On a deeper level, it essentially involves summoning additional force. a new very strong, high energy force, and that would also imply other very interesting things, in addition to possibly being a clue to explain this problem, it would also tell us that the Higgs is not an elementary particle at all, it is not fundamental, in fact made of other things, other exotic particles that interact strongly, so we would really fundamentally change our understanding of the standard model and it would be very exciting if this turns out to be real.

Now the people in my experiment are working very hard, they are all trying to get into this. area as you can imagine, including me, so I'm starting to make measurements like they're trying to make measurements like this. There will be updates to these articles very soon, so probably within the next year, certainly, within the next year or so, The answer to this question should come in very short time, so either we will confirm this effect or it will disappear and everyone we'll get really depressed but hopefully it'll be the first or not the second but it's a very exciting time to be in particle physics so definitely keep your eyes peeled over the next year or two because we should get an answer either way .

Thank you so much.