 But for now, I will leave you with John Butterworth from UCL who is going to talk to you about the Large Ardham Collider. Okay, thank you very much. Thank you. It's really nice to be here and thank you for coming in out of the sunshine to hear a bit of physics. I'm going to talk you through what's going on in Geneva at CERN, which is an experiment I work on, fraud based in UCL and there are many UK universities and others around the world who collaborate there. I have to confess, happy as I am to be here in Guilford, I have a certain amount of Chicago envy as you'll hear at the end, there's the biggest particle physics conference in the world every two years is going on now, ICHEP in Chicago, where there are some results have been announced today which I will finish this talk with. So this is very up to the minute, although the beginning of it is hopefully introductory enough that you can see where we get to by the end. This is happening now basically. The star of the show is this, this is the aerial view you would get as you approach Geneva Airport which you can sort of see as a beige smudge kind of in the middle of the picture at the top of that yellow ring. That's Geneva Airport on the horizon is Mont Blanc, you'd kind of be approaching it over the Jura Mansons in France and you can see the Swiss-French border zigzagging along there and that, the yellow circle there is marked, of course you don't get to see the yellow circle of course that the farmers would have objected but they wouldn't let us paint it but it marks the path of the tunnel of the Large Hadron Collider. It's about, it varies in depth at roughly 100 metres on the ground, it's 27 kilometres around which for those of you who are familiar with it is within a kilometre of the same length of the circle line and the right colour so it's easy to remember and going round it significantly faster than the trains are the two highest energy beams of particles we've ever managed to get together and control in a laboratory. They're both beams of protons and they're counter circulating, one in each direction and they're brought into a head-on collision at four points on the ring and you can see the mark there on the picture where it says Atlas, LACB and CMS and at each of those points we have essentially the biggest, fastest, highest bandwidth digital camera you can, we now have to build to record what happens when those protons collide with each other. I'm going to talk today to you about results from the Atlas and the CMS experiments which are diametrically opposite each other on that ring. Atlas is the one I work on, there are other people in the UK actually work on CMS and while the other two experiments are interesting, LACB and Alice, they're quite specialised experiments and there's good physics being done there, there's a lot of physics you can do with these beams but Atlas and CMS are what we call general purpose experiments so to be honest when we collide these beams together we really don't know exactly what's going to happen and that's kind of the point of the experiment. We want to know what happens when these beams collide and you don't therefore know exactly how to optimise your detector, you don't know what the most important things to measure are actually going to be so you throw all the technology you can at it and hope it can do everything pretty well and that's Atlas and CMS. So before I get into the science and technology of that, just to say a bit about the sociology and the politics, this lab CERN is a centre European research nuclear although the official language now is basically English. It was founded about more than 60 years ago in the aftermath of the Second World War to sort of try and rebuild the collaborative open science that had been going on before the Second World War. If you think about it in the early part of the 20th century, quantum mechanics, relativity, all the nuclear physics, all the advances in physics were coming from Britain and France and Italy and Germany and Denmark and various European countries. By the end of the Second World War, that expertise had been divided and dispersed and had gone a lot of it to the United States. Some of it had gone east and Europe really was in a mess and CERN was part of an initiative, it was independent of anything else, it was set up in the middle of Europe and Geneva to basically try and do, rekindle that basic science. There's no explicitly commercial idea behind it and also absolutely no military involvement behind it. It was completely supposed to be for peaceful curiosity-led research. Just about the last thing Winston Churchill did as Prime Minister of the UK was signed the UK joining as a founder member in 1954. And it's been going since, it costs about two euros a year per taxpayer in the European Union and for us of course slightly more pounds than that now. But it's, we've been paying roughly that into it for, it's actually independent of the European Union of course, but it's, we've been paying roughly that into it for the last few decades. It started smaller but it's been flat for the last few decades. But it's been a very steady and long-term investment that's very stable because it's done by international treaty. Whereas for instance in the US the budget is set annually and there's always a big fuss about it. And the fact that there's that stability has allowed it to really succeed and to the extent that now every country that's coloured in here has some formal relationship with, comes there to do science, it is really the one place in the world where you do this really high-energy physics. So, how do we do it? Well, we do it. This is a pictured engineering blowout kind of cartoon of the Atlas Detector. You can see it's got a sort of cylindrical structure and each of these concentric cylinders is telling, is designed to tell us something different about the particles that are produced when you collide these protons together. I'll show you a picture of this in the moment but when you collide them there's all kinds of stuff produced there and you really, the name of the game is to work out what particles were produced, what their energy was and where they were going basically. So I won't go into it in huge detail but the central part, the central cylinder there is a semiconductor detector which is kind of, there's lots of very smart ways of using semiconductors here. This is a fairly stupid way in that you just leave it doped with a voltage over it so it's actually an insulator but it takes a very small amount of energy to free an electron and create an electron-hole pair which means you get a current released and that means you can tell for a very small expenditure of energy you can tell that a particle went by and that gives you the track of the charged particle. Then around that there's a calorimeter which in Atlas is liquid argon but the point is it should be something that's very dense but also allows light and electromagnetic fields to propagate through it so that when particles stop in it you get a shock of an electromagnetic field and that tells you what the energy of the particle was. And then the big wheels on the outside are there to detect muons which are punched through the calorimeter because they're sort of like electrons but heavier. So but that's the kind of, that's the only other thing really to say about that. You can see the beam pipe with one beam of protons coming one way one going the other way. Most of the protons actually miss each other but some of them will collide right in the sense of that cylinder. The others all go around the ring again and have several more goes. And the other thing just in case you haven't spotted it there are a couple of people standing on the beam line there and down below so it's pretty huge. It's basically a cathedral for particle physics and this is one of the kind of iconic images of this that went round when we were building it. This is from 2005 before it was finished. You can see one of the people who was building it in the middle. The kind of pictures he gives us are like this now. So actually UCL was one of the teams that built, that wrote the software for the event display that you're seeing here. I think if we'd have known that it was going to be shown in so many papers and things when we got the first results we'd have probably hired a graphic designer as well as some programmers but never mind. It does kind of work and if you go to Geneva and you've got a couple of hours to kill at the airport CERN isn't really very far away from the airport and there is a, if you're really into this kind of thing you can go and see the Atlas Control Room. There's a visitor centre with a glass wall. You can press your nose against the glass and watch physicists at work and you'll see these events on the screens in the control room because they actually do give us some diagnostic information about what's going on underground where the collisions are happening. What you can see in this one is three representations of the same collision there and if you look at the circular one first in the top, was it your top left of the screen, that's a slice through that cylinder and you've got to imagine one of the beams coming from the back of the tent, the other coming from behind the screen, they collide in the plane of the screen and you see all those lines are all particles produced in that collision. The ones that are greyed out and bending, they're lower energy and they're being bent by a solenoidal field and because they're lower energy it can bend them but the yellow lines are hardly bent at all and that shows you that they're very high momentum and they punch right through the calorimeter which tells you that they're muons in fact and they're registering the muon detectors on the outside. The smaller image there is the other slice, this kind of more rectangular one is the other slice through the cylinder and you can see the same two muons there and if you zoom in on the red dots where the beams collide then what you see is that mess at the bottom of the screen and each ellipse there is a source of particles and it tells you that there wasn't just one pair of protons collided, there were many, about 12 actually in this collision and we get many more these days. The protons don't come one at a time because most of them miss so it would take too long to collect the data if we did that and in fact they don't come in a continuous stream either, they come in bunches about two centimetres long and thinner than a human hair every 25 nanoseconds, every 25 billionths of a second and that actually tells, I'm not particularly good at numbers for a physicist but I know the speed of light is 30 centimetres per nanosecond and if you think how big the detector is that tells you that these particles even if they're travelling at the speed of light do not have time to exit the detector before the next lot are coming and then the next lot and then the next lot and that's even before they start reading out, we start reading out the detector and getting the signals down the cables also at the speed of light to the, we have basically an office block full of computing next to this downstairs then there's a tier zero computing centre at CERN which is another two or three office blocks full of computers and then it's farmed out around the world on a computing grid where there's a tier one centre in every major collaborating country the one for the UK's and the Harwell and Digcutt near in Oxfordshire and then it gets sent to tier two centres which are basically universities and finally ends up on our laptops and we do physics with it so when it's running that's going 24 seven all the time and there are people on shift all the time doing that and all the data is shared with everyone on the collaboration there are, the first paper we wrote based on this was four pages long physical review letters unless you included the authors in which case it was more like 20 pages long because there are 3,000 authors on each of these papers sociologically that's a bit tricky because not you worry about people getting the credit for the work they do on the other hand if we argued about who went on which paper it's such a close knit collaboration that we would never publish anything because we spend all our time arguing about the author list so we essentially give up and put everyone on it okay so why do we want to go to high energies it's actually obviously going to high energies is expensive the ring the reason the ring has to be so big is quite easy to summarize because it's basically Newton's laws the problem with these beams is actually not getting them up to high energy the problem is making them go around in a circle the century people force you need to apply to make these beams turn a corner is huge it's higher than anything we've ever needed to do so this tunnel is actually stuffed with the most powerful superconducting magnets we know how to build once you've done that the thing that limits your energy is how sharp is the corner you want to bend the thing round which mitigates a huge ring that's the big big purely for the same reason that curves on a motorway corners on a motorway are gentle so you don't skid off will be bad if these beams skidded off so that's why it's big because we want to go to high energy but why do we want to go to high energy and I've got a massively sophisticated video to show you to illustrate that what we're essentially doing with this machine is we're looking more closely at oh dear let's see if this is going to work bear with me a second it usually does okay damn it okay maybe it's not going to work I'll try once more if it doesn't then we'll move on it's not essential I can even work out how to move on that excuse me I'm not sure this video is really worth the effort in the end but that's not good okay stop it the point of the video video is on your ripple tank with water in it and it would be nice if I can show it you but I can't by the looks of it hopefully I can get back to the rest of the slide help it's not it's not displaying I don't know why is it thank you okay so forget the video what a video was going to show you was it was essentially illustrating the fact that you can't see things unless you have a wavelength that's smaller than the thing you're trying to see so what it was was I'm going to do the video with my hands I think that what it was was a ripple tank where you've got waves traversing it and you see if you put a blob in the ripple tank you will see that the blob leaves a shadow and the waves can be you can detect with the screen behind the blob you could tell the blob was there you could measure the size of it probably and the shape but if you drop a second blob in which is smaller which is smaller than the distance between the peaks and the troughs on the waves then it becomes invisible the waves kind of reform around it and you can't see it on the screen and that's that gives you an idea of what's going on in in these experiments what you see what you would see on the video then is that they increase the energy they ripple it faster and they shorten the wavelength increase the frequency and at some point the blob the smaller blob becomes visible again because you've increased the resolution by increasing the energy so the point of that little demo was to say that we need to go to high energy because high energy means high frequency and that means short wavelengths now so for instance radar has got wavelengths of meters is great for seeing ships and planes but if our eyes were sensitive to radar we wouldn't be able to see each other we are sensitive to hundreds of nanometers so we can see fairly fine detail if you want to see smaller than that use x-rays or electron microscopes or something and you can think of the large Hadron collider these particle colliders is essentially the end of that chain basically with it it's the most powerful microscope in the world in the end and that's by virtue of going to highest energies which means the shortest frequent the highest frequencies which means the shortest wavelengths so what do you see when you when you do that this is what you see this sort of Lego Minecraft version of the standard model this is as far as we know these things what everything else is made of and these things themselves are fundamental that is not made of anything else all that means really is no experiment we've been able to build no matter how closely we look at them we've never been able to break them we've never seen anything inside them we've never seen any internal structure so for all for in our theory and for all practical purposes they're infinitely small fundamental particles the red stuff at the top of the quarks you see the open the down quark which are what make up protons and neutrons in different combinations the electron is below them and it has a neutrino with it neutrinos don't interact very much but they're produced in beta beta radiation beta decay they're also produced very copiously in the sun there's a lot of them in this room but they don't make much noise that column actually I've just described with protons and neutrons I've just described everything you need to make an atomic nucleus and you add the electron then you've got a whole of atomic physics and chemistry and the rest so it's a bit of a puzzle actually that is copied again three times you've got the charm and strange quark and the muon which I mentioned earlier you saw those yellow lines on the collision diagram and then the top quark and the bottom quark and the towel at on and they have neutrinos with them as well and then the purple stuff on the other side is how these guys interact with each other so the photon is what you're seeing me with now it's the carrier of lights it's also the carrier of the electromagnetic force it is the electromagnetic field if you like then the glue on the G there is what sticks to quarks inside protons and neutrons and sticks them inside the atomic nucleus and then the W and the Z carried a weak nuclear force which is a bit of a tricky one to describe because it's so short range it never really gets outside the nucleus so it's a bit esoteric on the other hand it's the only one that the neutrinos experience and it's also is absolutely essential in processes that keep the sun going so that's why it's produced neutrinos are produced in the sun so it's kind of important even if it's not that obvious in everyday life so I'm going to show you the data so there's a problem that comes with this though and that's this gray blobby thing in the background which is it's quite hard to see how something that's infinitely small can actually have mass can actually have substance at all and for instance the Z and the W on there are about 90 times heavier than the proton which make it's very hard to imagine when they're supposed to be infinitely small and that was that was a problem that was realized even before we knew about quarks it was realized that in actually in the matter not it's not just a kind of intuitive problem that is hard to give such small things mass it's actually a problem built into the mathematics of the theory that behind all this and even in the early 60s before we discovered quarks people were worried that this was going to be a long-term problem a fundamental problem with the theory and there were Francois Engler and Robert Brout in Belgium and Peter Higgs in Edinburgh were worrying about this and came up with a solution which was to fill the whole universe with a new energy field because that's the kind of thing theories can do and and say that the mass is not something the particles have intrinsically really it's that something they get by interacting with this with this field and by a sort of mathematical slate of hand that made this whole the whole having mass thing work made the mathematics of the theory consistent actually Brout and Engler got there first by a few weeks independently of Peter Higgs so you might wonder why there's a big H on there and why it's cut why we talk about the Higgs Boson and that's because he was a bit lucky actually he wrote a term a bit more explicit in his paper which is do with the experimental evidence I don't know about you I'm an experimentalist and I don't know about you but fill in the whole universe with a new energy field is a bit of a leap just to make the maths come out right so I'd like a bit more evidence for it now a field like the electromagnetic field or whatever is what physicists use to describe it something that just fills space and has a value everywhere so there's an atmospheric field in this tent which has a temperature and a pressure every point in the in the in the volume of the tent and in the same way that the Higgs field if it's there will have a value at everywhere in space and detecting whether that feels actually there or not it can be tricky I mean for the for the air in the tent it's easy enough if there was no air in the tent not only would you not be paying much attention to me but the you wouldn't actually be able to hear me because the one of the reasons we know the field is there is that sound waves are traveling through it there's a pressure wave traveling from my mouth to your ear or from the speakers to your ears which is is it evidence that the field is there now it turns out that's the only way we know how to prove whether the Higgs field is there or not is to basically hit it really hard and make a ripple in it make a wave in it and that ripple it's actually a quantum ripple it's a quantum excitation basically makes it a particle that ripple is the Higgs boson and Peter Higgs wrote that a little bit more explicitly in his paper that became the experimental linchpin of the whole thing which is this whole theory of mass is right then in the end if we hit the universe hard enough we should make a ripple in it which is the Higgs boson and that's one of the things the LHC was designed to do so I'm going to show you the data that shows that that was right I'm going to this is the most technical bit of the talk I'm going to show a couple of Feynman diagrams don't panic if you'd not if you don't like them come back in a minute but these are the cartoons that show us that we use to represent the calculations of a collision so we're talking about colliding particles together we predict probabilities that a given thing will happen and then we compare it to the data we just count how many times it happens and if it's right the theory wins and if it's wrong we win this for every term in this every line and dot in this cartoon there's a term in an equation that goes with it but what you can see that basically is an electron and a positron coming in annihilating making a photon which is a wiggly line in the middle and then decaying back again to an electron and a positron and there are three bits of physics that come into play here that actually are in a parent contradiction with each other first one is the only equation in the talk I think first one is energy is equal to mass times the speed of light squared fine it's true the other is energy is conserved so there's a lot of energy goes in from the collider and there's a lot of energy goes out again because you measure it in your detector so there must be a lot of energy in the middle in the photon and then the problem comes from the fact that the photon has got zero mass and c squared is a big number but if m is zero then the energy in the middle should be zero which would mean that energy is not conserved which means physics has a hissy fit so how do we get around this we get around this by the fact that this is quantum mechanics which is slippery and in fact all we do is measure what goes in and what comes out so the stuff in the middle is in a sense not real you need it because if you don't put it in there you'd get the wrong answer in the equation but you never actually measure it it's a kind of possibility in quantum mechanics and in fact you have to sum over all the possibilities in the middle of that diagram to get the right answer and because it's not a real particle then the photon is allowed to have the wrong mass so it doesn't have zero mass now there's a remnant it's I know this sounds a bit odd is that there's a remnant of reality in this because the further away from it is further away it is from its correct mass the less likely the thing is to happen but it's still there it can have the wrong mass it won't be a zero probability if it has a wrong mass so this looks like a bit of a silly experiment to do if the energy is high the photon has to be a long way from its mass so it's actually very unlikely to do this but there's another particle in there called the Z boson which you saw earlier which does have a mass of 90 times the mass of the proton roughly so if you tune your energy upright you can make those three things hit the sweet spot you can say the Z has the right mass equals mc squared and energies conserved and they all work at once and then the probability will be very high so this plot shows that all those things I just told you you see at the far end the probability so what you've got in the vertical axis is the probability of it happening in some strange physics units and what you've got along the horizontal axis is the mass of the wiggly line in the middle and you see the probability is very high on the far side the photon would have roughly the right mass there nearly zero as you go up and up in mass it drops very very quickly that's a logarithmic scale and then there's this huge peak where the Z boson is where suddenly the Z has the right mass and you see this kind of resonance appear that the probability peaks where all those three things come together and the particle works and that's a very generic feature of doing physics at colliders if you see a peak in a probability that probably means that in all the mess of possible Feynman diagrams you might have described in the collision there's a new particle popping up and that's what's causing the peak so that's how we look for the Higgs boson as well not in precisely this experiment but in one rather similar we look at what the Higgs can decay to it decays very very quickly if you produce one so all you you can't kind of get them in a jar and keep them for later you have to see what it decays to measure what it decayed to and work out what its mass might have been so one of the things one of the possibilities that it can decay to is a pair of photons and those are those yellow blobs you see in the green ring there there's a couple of yellow blobs not looking terribly impressive but if you look at a little histogram on the side of it you see that they've got a huge amount of energy compared to the rest of the event and the green bit at the bottom there that's just zooming in on the yellow blobs you can collect you say two photons it might have been a Higgs it might not we've no idea but what we can do because we can do some relativistic kinematics and we've measured their energies is we can say hypothetically if it had been a Higgs what would its mass have been and we can put we can plot that mass in just the same way as on the previous plot and here you go this is two years of my life you can see the date ticking away in the top corner there this is the horizontal axis is the hypothetical mass of a Higgs if it was there the mass of the pair of photons if you like number of times it happened on the vertical axis lots of statistical noise but as you get more and more data that dies down and then in the middle you have a little bomb that doesn't go away that's the Higgs boson now it's not super impressive I realized but it's kind of telling us a lot about the way nature works I remember on 3rd of June 2012 which is the day before we announced the discovery I was in CERN watching the data put together by our spokesperson Fabiola Ginati and it was really exciting to watch and then I had to go to London because I was head of the UK bit of the experiment and we had all the politicians in Westminster to talk to and my opposite number on CMS was also there Jim Verdi from Imperial and just before that whole thing kicked off he showed me his top secret data and I showed him mine and this is what they had and this is the same bump in the same place and I honestly thought that I believed our data but I must say I got a certain wrench in the gut when I saw that the other guys had confirmed it I think it's quite surprising because we thought we'd done all the checks we could and I really thought I believed that Atlas had found the Higgs but it wasn't until I saw CMS had it too that I really actually at some level believed the result where nature was telling there's something very profound about the way the universe works there remember what that is that bump is the sign that there's a new particle entering in these Feynman diagrams which is the excitation in the Higgs field which is the evidence that this energy field that fills the universe is really there which tells us that we actually understand where the massive fundamental particles comes from so it's quite a big deal for a little bump so where are we now well I sort of lied when I said that this is what everything in the universe is made of one obvious thing that's not there is gravity isn't included this is beyond the standard model it gets worse because even if you include okay we have a theory for gravity it's called general relativity if you include that in and the standard model then you allow those two theories to co-exist which they don't do very comfortably anyway but if you do then you start looking around in the universe and you find out that even with those two we don't understand how galaxies move we don't understand the distribution of matter in the universe we say there's something else out there called that matter but we don't know what it is it doesn't seem to be made of any of the fundamental particles we know of there are various other things we don't know why the universe is predominantly matter not antimatter because when in a collider we typically make equal amounts of both of them so there are a bunch of open questions we have an odd situation the standard model of particle physics is sort of complete and internally consistent but it's obviously not a theory of everything so we're looking for clues that will give us a bigger and better theory and so we go onward I'm just going to skip over these but we're looking to we're looking for bumps all the time and excluding them until yesterday or this morning even I would have been showing you this and saying oh I wonder if this is a bump there so you see there's a bump 750 GeV similar kind of plots are the ones I've been showing you before it's not statistically completely significant but it's Atlas and CMS and maybe indicative of something going on unfortunately it's gone away as of today oh I thought I had oh yeah sorry I've lost the slide oh dear I had some data that was shown actually today in Chicago but unfortunately it's an update on this which shows that particular bump has gone away which is a bit sad there's another one which hasn't gone away yet as far as we know which is this one 2000 times the mass of the protons statistically marginal you saw the animation you saw there are all kinds of noise and bumps and things and a lot most of them go away so we've got all kinds of stuff like this going on trying to not get too excited about shimmers in the statistics but on the other hand trying to take them seriously if they if they happen and if they do happen they'll be on the standard model there might be a clue to some of the missing pieces that we don't understand in there the the good news is that the Large Hadron Collider is working extremely well what you see here the blue line is the data we got at lower energy in that we discovered the Higgs width the pink line that's going up above it now is what we're doing right now this year at very high energy if that carries on then a lot of this statistical noise will die away and if there are any bumps there we'll probably find them so it's it's good this is going on right now this is where the data I was I was going to show you but seems to have lost there has just been shown today this morning in Chicago so just about an hour ago in fact unfortunately what it showed was one of those bumps vanished already but there's other stuff going on there it's a very exciting time actually to be doing physics so I was going to finish there just one thing I will say since I saw the end of the previous talk which is all about miniaturization of computing or one of the things it was about was miniaturization and computing with the the pi zero at the end of it we don't seem to be doing that this is a picture of the Large Hadron Collider there's the little ring on there and this hundred kilometer dotted line is what we might build next there's a view of it from the Jura Mountains here but actually that's not a full story it's not just about being digging bigger tunnels and what you see in here is actually an accelerator on a chip that's a human finger it's on and this this chip can get higher accelerating gradients than anything we have in the Large Hadron Collider it's got nanoscale serrations in there which if you fire a laser transversely to it will give you really high electromagnetic accelerating gradients so if you strung a lot of these together you could probably get the energies of the LHC in about 30 meters rather than 30 kilometers there's always a catch the catch is you need very big lasers to fire transversely to it but it's just to give you a flavor of the fact that it's not just about building bigger and bigger tunnels it's also about being smarter with the technology and that's something that goes on a lot as well at CERN and at UCL and with that I think I'll finish and I've got time for some questions if you like if if you have questions please raise your hand and I will bring the mic to you just a quick one you talk about using protons wasn't there talk at one stage about using other nuclei as well lead etc to take take the energy up for the set higher energy for the same speed yeah so I trouble hearing because of this but that you're saying using other other nuclei and other particles yeah we do so it's called the Large Hadron Collider not the Large Proton Collider because we do actually put lead atoms in there lead nuclei in there sometimes they get to higher energy because they've got a higher charge so you can accelerate them more on the other hand they the energy per nucleon if you like is not as high so in fact they do slightly lower energy physics bizarrely the whole game is about density of energy really not the total energy so the density of energy in a lead lead collision is actually lower than a proton proton collision so they won't find the higgs for you but what they do do is you create this stuff called quark glue on plasma which actually is more of a liquid it seems but which is a kind of another stage of the early universe it's a kind of exotic form of matter where quarks and gluons are essentially free rather than bound inside hadrons and new hadrons and bound inside hadrons protons and neutrons or whatever so there's good physics you can do with that but paradoxically although the beams are higher energy in that configuration the resolution if you like that you're accessing is actually lower the energy is lower so and there are also colliders with electrons which get to quite high energies but not as high as protons and there are discussions about muon colliders which will potentially be very nice but have technical challenges shall we say any more questions seems to be one at the back though is there someone raise your hand okay just a question about weekly interacting particles like neutrinos for instance right so I understand that you know that they are streaming through our bodies all the time right so they you can't shield for them right so they must also be interacting with the beam at some point does that is that something you can or you do observe or as it we have to observe we don't observe neutrinos in the LHC we indirectly know they're there because we surround the beam with a detector so you can from the fact that something's missing you can deduce that probably you had a neutrino so there's an imbalance in the momentum in the final state of the collision so in that sense we do measure at least missing energy which is then probably neutrinos and we can test that it might actually be dark matter so we're always alert to the fact that we might have created a bit of dark matter and it fakes a neutrino because that also doesn't interact with the detector there are dedicated neutrino experiments I mean the trick with detecting neutrinos is to have a lot of detector and a lot of neutrinos and then eventually you'll see one or two of them so there's an experiment actually in Chicago firing a neutrino being from Fermilab through Minnesota into kilotons of iron scintillator and they get a few neutrinos a day when they're firing billions and billions and billions of them and there are also experiments that did detect the neutrinos from the sun there was a big puzzle for a while there didn't seem to be enough neutrinos from the sun and they built detectors to check that and in the end they found out that's true there were not enough electron neutrinos from the sun but there were changing type on the way here which was an important clue as to the maker of the standard model and the fact that neutrinos have mass in fact so neutrinos are extremely interesting but we don't do a great deal with them at the LHC because we don't make enough of them you need a lot of them to actually do anything with them Any moral questions? So if neutrinos don't interact with anything how do you make them into a beam? I know it's not uncertain it sounds interesting Yeah they go in a straight line that's for sure you don't bend them for the magnet what we do is you start with protons in fact so you smash protons into a target of some material some atomic material and one of the hadrons that's really copiously produced in those in when you do that when you smash a high-energy proton beam in is a pion which is a quark and an anti-quark pair and they are some of them are charged so you take the charged ones of those you put them in a beam you collimate them you point them where you want them to go and then at some point they decay into a neutrino and an electron or a muon and you rely on the fact that the energy you've pointed them in the right direction before they do that the mass of the pion is quite low so the neutrino will carry on in roughly the direction the pion was going in and then you see you have this kind of beam of neutrinos fanning out but definitely once you've got a neutrino it's going to go the way it's going it's not going to be changed in direction you can't control it there was maybe one last question so any hypothesis on what the two tev peak could be if it's real and what's the name of that accelerator on the chip ah the accelerator on the chip I know it's not been built as a working accelerator yet I think there are there are prototypes for low-energy beams for medical applications but it's not there's no working particle physics thing so I don't know I'm afraid the name of it it was built by stanford linear accelerator lab so you can probably find out from there what the there's a technology group there that did it but I don't know whether they've named it or anything yet the the other question what was the other question sorry I can't sorry the two tev peak oh yeah sorry I've got memory like a goldfish the two tv peak it looks like it what it is the way we see it there if it's real is it's in a pair of w or z bosons so it's some really heavy thing that decays to a pair of w and z boson or z bosons there's no off-the-shelf theory for that it's not obviously something like super symmetry or whatever but there are there are models there are models even with extra spacetime dimensions where it's some kind of higher higher geometric excitation of one of the particles we know really out there stuff but it doesn't actually if it's real then it will it will kind of throw try the cat among the pigeons amongst the theorists because it's not one of the things they're waiting to tick off it's it's a bit unusual so with the with the diphoton bump even though it's now gone away in the brief period it existed we had about 500 theory papers trying to explain it if the if the two tv bump doesn't go away then there'll be a similar number trying to explain that as well if not more that's kind of the joy of being an experiment is you write one paper and then it gets cited 500 times by people trying to explain it there you go hi so just from an engineering question atlas is a very big machine and you've got quite a lot of energy going in there in the interaction what kind of maintenance do you have to go to or what damage does it get what what kind of what's what kind of damage does the detector get and what kind of main damage yeah what kind of maintenance do you have to put under yeah it's we have to take particularly for the the bits at low angle to the beam and close to the center you have to say radiation damage into account and there was a lot of R&D done before before we built it to try and make sure that the the front end electronics would be robust against that there's this kind of what they call a Lazarus effect where you sort of anneal it anneal it with in a test beam and event and it goes to a performance dip where you get the the defects build up in the silicon and and it disrupts it and you get a very bad signal to noise ratio but then at some point it seems to anneal out and recover some of its initial performance so everything that was put in there went through that process basically to at least the silicon did to to blast it like that even so there's a lifetime and if we want to carry on taking data beyond about five years time with it we'll probably have to replace most of that silicon in the middle of it and we've already had to replace some of the electronics it's quite near very near the beam pipe kind of quite a distance from the collision but but at very low angles so there's a lot of very high flux of particles there and it really does cause damage so it's a it's a serious issue although CERN is explicitly non-military it got a little iffy at some point because a lot of those requirements for fast electronics is radiation how they're actually common with the nuclear industry some of it is civil and some of it's pretty uncivil so we had to watch what we were doing there in terms of negotiation but there's the interesting stuff there we still have time but four questions but if if there's no more maybe we start maybe you should stop here but i'm gonna go over to the info tent and if anyone wants to carry on talking they're welcome and also this is a book i wrote about the Higgs Discovery and i've got some of them for sale if you're interested as well so okay all right thank you very much