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Produce Doctor, a professor doctor, Dr. Robert C. Helling from the University of Munich. And please give a big hand for his presentation here on one of the most confusing topics that I ever had to read about when I was doing physics, which is supersymmetry. Thank you very much, Dr. Holly. OK. Thank you for coming to this prime time talk on day two. Yes, I am. My name's rover telling. I'm a physicist at Munich University and this talk is by request of a local brewer. Hacker asked me to talk about supersymmetry. So who knows? These people just got an idea. I'm over 40. Who else is over 40 for particular, this lady? You all know her, but who recognize her? It's Madonna. Yes, it's a I can 80s movie picture. OK, so what is supersymmetry? We are talking about particle physics and supersymmetry or Susie. And chart is a symmetry that predicts that for every known species of particles, there is a new particle and not a single one of them has ever been observed. So why bother? And I will probably spend forty five minutes to explain why bother us? So I want to explain why my colleagues have come up with this idea of supersymmetry because it solves some of the big, outstanding problems in particle physics and theoretical high energy physics and in general. So but I have to explain a couple of things. So a brief introduction of first, the known players that is the standard model of particle physics that consists of matter particles, namely the leptons of they all have spin one half. This is the spin. That's the angular momentum, the intrinsic angle angle, the momentum of the particle. Most well known of this, these particle is the electron here depicted as E. And there are also neutrinos you might have heard of about those because there were some rumors that they could travel faster than light that turned out to be a problematic cable. But these two? So this one is everyday physics and chemistry. This one is very light. They have heavy, the electron is heavier partners, and ther
e are also neutrinos for these part, and it's called This is the meal on. This is the town. And then in addition. So these guys make up the hull of an atom, and the core of the nucleus of an atom is made up out of quarks and neutrons. And those consist out of quarks, namely of these up and down quarks, but that form more types of quarks called chom strange bottom and top. And then there are four forces in the universe. One is gravity that doesn't matter for elementary particles. The others are mediated by particles again. Those have spin one, and the most well-known is the gamma particle, or the photon that's responsible for electromagnetism. But that's also the W and the Z vector boson that mediates the weak interaction that is responsible for beta decay. And there are gluons that actually keep these quarks together in the nucleus then. And then since this year, we know that there is actually another particle of spin zero and that's called the Higgs boson. And this year, the Nobel Prize was given for the discovery of actually for the prediction of this particle. So that is the standard model. These are the particles that we have all by now seen, and they fit well into this model called the standard model. Now come supersymmetry and for each and every one of those, there's a new partner. So now we're talking about the minimally supersymmetric star model that minimally refers to. We're adding as little as possible. So for these, X equals one half particles we add as equals zero particles called this leptons. You get their names by adding an X. So that's the electron, that's the smidgeon. And that's the star as well as the squawks. And then to these force particles that are fermions with SW equals one half called the photo for the photon, the winos and the Xenos for the W and the Z. You see the way adding an igloo we know are actually several one for the gluons plus Higgs, you know. And to make things internally consistent, this doesn't quite work. We have to add anot
her pair of Higgs and Higgs xeno to make things work. So this is the minimally supersymmetric standard model, and I will be talking mostly about this set up of elementary particles. These. Has covered these hypothetical, and then there's an important principle and quantum physics that particles are fields. So there's the this is the electromagnetic field, but it's described by photon particle and the fields are again particles. So I will and the rest of the talk. Use this synonymously. OK, so I claimed there are open problems that are solved by assuming supersymmetry is a symmetry of nature. And I have five of them listed here. The first is actually very close to my heart. Up when I'm actually doing research, that's the mathematics of quantum field theory. But unfortunately, I won't talk about this. I'm the next one. This will take quite a while to explain it's called naturalness. Susie provides a solution to the natural problem, and to explain this, I have to go on a small detour. I have to explain how we theoretical physicist in the 21st century view these force fields, in particular the electromagnetic field. So this is how everybody learns what electromagnet magnetism is. You have a wonderful generator and that makes your hair go up and you have charges and force fields. And this is this electromagnetism 101. But I want I. I ask you to believe me that there is a completely different point of view that actually talking about the same thing than electric and magnetic fields, and that goes like this. So let's assume so. This is space the hammer CCH dumped to a bahnhof plant and blown, and at each point in space, that's a virtual or internal plane attached to each point in space. So far, five by five. My point is dying, but for five by five points, I've drawn these spheres. Not not spheres, actually, that whole planes and they have a rotational symmetry. I can rotate the plane around the origin, so let's do that. So now I hope everybody can see that these guys are r
otating around the origin and rotating. Yeah, yeah. You got it. Get an idea, at least the people in the front row. But the important thing is, so now they're all rotating in the same way, they are all rotating in parallel. But you can rotate them independently. So now this starts, then the others come on. And so you see that each one is rotating separately from the other. So this movie that you see here is actually a depiction of an electromagnetic wave traveling here from once this southwest to northeast. So here it goes again. OK. And I claim, and I have to ask you to believe this. I cannot explain this further that electromagnetism is nothing but the description of these rotations. So you have a description of these rotations. I'm talking in an equivalent way about electromagnetism. This is actually a representation of Maxwell's equations. If you happen to know what those are. So in particular, there is some somewhere in these rotation. That's the Coulomb law that describes the force between two charges. But I'm claiming this is contains all the information about the electromagnetism, how all these planes rotate. OK. So and and the point is not only electromagnetism is about of this type. So electromagnetism is a rotation of a plane. Here you see the plane rotating, but also the weak force. Remember Decay, K, W and Z bosons? This is also about rotations, but those this force is not about rotations of a plane. This rod rotations in a three dimensional space. So if you like of a sphere, so this sphere here is rotating about different axes and that's and coating the weak force. So weak force. So technically, it's not the this group that rotation was assumed to. There's also the strong force that is about rotations in a complex, three dimensional space, and I don't have a better picture of this than hyperspace. But the principle the mathematics is the same is just high dimensional. OK, so that is I claim these these are all the forces in the universe. Maybe, except g
ravity are just rotations of some sort of internal spaces that are attached to each point in space. OK. These are the forces. Now comes the Higgs effect. So what so you told you a Higgs particle Nobel Prize 2013? I explain to you what the Higgs effect is very simple. In addition to the plane, there's a little blue ball in the plane, and the Higgs field just tells you where in the plane the ball is. So right now, it's in the origin, right? But I can move in principle. I can move the ball around to any other point in the plane. And the notion where the ball is that is the Higgs field in the same spirit as the rotation of the plane is electromagnetism. And now we add something to this plane, we add a potential energy, so kind of landscape, so let's turn that on. So this now looks a bit like the bottom of a champagne bottle. So I've added some potential LNG, but this is still rotational asymmetric. So now rotational symmetry is still intact. Now you have these champagne bottles with a blue ball in the origin, and this thing is still protection symmetric. The wave goes through Hamburg. Hello. OK, but of course, the ball at the tip of the champagne bottle is not the minimal energy configuration the ball wants to be further down. You can gain energy by bringing the ball down. So let's do that. What now you see the balls at the bottom? So and of course, there's more than one possibility to put the ball at the bottom. There's a whole ring of possible places where the ball can lie and a minimal energy configuration. And each one of them, each choice for possession of the ball on the bottom breaks the rotational symmetry. Wherever I place the ball, the symmetry is broken. So now if I rotate these planes with the ball, as this happens here, I have to drag the ball around and that costs energy and this energy. This turns out to be the mass that is given, so the symmetry is broken. And this is how mass is created. The mass is actually the energy it costs to drag the ball around w
hen the electromagnetic wave goes through this configuration with the broken symmetry, and that is the Higgs effect. This is how the Higgs effect gives mass to elementary particles. And so, OK, so when I said this happens in electromagnetism, this is actually not true, I lie to you in electromagnetism, the symmetry is not broken and the photon is mass remains massless. That's good because otherwise it couldn't travel long distance. You couldn't see me of the photon where massive it would decay before it reaches the photon that comes from me or from the screen would decay and would not be there if it would be massive, but it's massive so you can see the screen. But the Higgs effect takes place for the weak interaction. Remember, that was the one with the rotating ball, but then with the ball, I couldn't draw the the potential, so I chose to use this representation. But it happens for the for the weak interaction. And this Higgs effect makes these Z and W bosons that mediate this force. It gives them a mass of roughly 100 gig electron volts could get electron volts or electron volts. Is the energy unit the particle physics physicists use? That's very convenient, so this is an important number. Remember this one hundred GeV? OK, and this mass corresponds to the distance that the ball has from the center. So. So that's kind of the radius of the of the motion of the ball that I have to drag around. The further it's out there, the more difficult it gets to direct the ball around. OK, so so that was the Higgs effect and gauge interaction, so such interactions are called gauge interactions. German speakers call them, I call. OK. OK, so now for something completely different. That was my first explanation, this is how electromagnetism and his friends work. Now comes a different concept that's called ring normalization. So now I'm for second. I'm back to the old picture. This is supposed to be an electron and this is supposed to be the antiparticle of an electron positron. Th
is is just like the electron just with positive charge instead of negative charge. This has nothing to do with the super fast. This is all standard model physics and the wiggly lines have drawn. Here is the cooling field. That's the electromagnetic field that drags the this violet ball towards the Red Bull. And everybody learned in school that this force that the force of attraction between the balls is proportional to the charge of the electron and it scales inversely with the square of the distance. That's cool, MS Law. Everybody should have learned this in high school at some point, hopefully. OK, cool. I'm sorry this everybody knows. OK, so now this this picture, this was classical physics. This is the first to learn in school, but the world is a quantum world and it's more complicated. The upshot of of of quantum mechanics is that the charge of the electron actually depends on the distance at which you look at it. And this comes about as follows. So quantum mechanics says the vacuum is not empty. Oh, not a lot of bottle for some. OK. You fell asleep. No problem. You were OK. Everything OK, OK. Back to quantum physics. Quantum physics says the vacuum is full of virtual pairs of particle particles and the antibiotics. They pop out of nothing and annihilate again. So I've drawn a couple of those here. You see the original electron, the original positron. But there are a couple of other electron positron pairs that have popped out of the vacuum for a split second. But these particles are also charged. Posit the the red one is positive and the the the purple one is negative. The other way round red, negative, purple positive. And they also see the electromagnetic field of this electron. So the purple one likes to go towards the Red Bowl, and the Red Bull likes to go away from it. So, so, so they align a little bit in this field. You see that the purple one's always closer to the red ball in the virtual positron electron pair, then the electron. So that causes someth
ing like a polarization of the vacuum and that yields shielding effect. So now this positron that was supposed to see the electric field of this electron not only sees the electric field of this electron that I've drawn here, but it sees also the electric field of all these other virtual particles and because they are aligned in the original field. Turns out, the field at this particle size is actually a little bit weaker because it's shielded by these other pairs, and this shielding effect is stronger. The stronger the the first field is because the stronger the so stronger because you are closer. So when you're closer than the alignment is even stronger and the shielding effect is even stronger, and you can subsume this by saying actually, so I total all these that charge and the shielding into a new charge called the re normalized charge. And that is then the charge that depends on the distance. Ah, so now the electric field e is proportional well at distance AH is proportional to the charge corresponding to the particular distance. Here are is this or some here to here. Divide it by all squared. That's the upshot of your normalization. That's a quantum version of the rule of law. So now how does Q of our look like so so that that's called running couplings because the well, the charge is special. Well, I mean, it's one example of coupling and it's running because it depends on the distance. And a similar effect applies not only to the charge of particles, but also for other properties of the particles, for example of the mass, also the mass of a particle like five and 11 K.V. for an electron. That's not the full truth that depends on the distance, the distance at which I measure the mass and for almost all properties. This dependance of. Are logarithmic. So there is a coefficient called beta, the so-called beta function times the logarithm of our logarithm, as you know, the function that grows very slowly with R and this coefficient theta depends on particular t
ypes of of the particles that are participating in this shielding. So you have to you can calculate this actually and depends on all the types of particles that can pop up from the vacuum. And also another property of a particle is the shape. Remember, the champagne bottle are the shape of the potential, and that happens to depend not logarithmic Li like the charge or the mass, but it depends quadratic li on the distance. So it goes more like some coefficient times are squared and our squared is a function that is much more sensitive to our than the logarithm you change. Our little bit logarithm stays mostly the same. We change our little bit, but the square of that change is actually quite a bit so. And because the mass of the W inset bosons, remember they came from the ball that it was not in the center, but somewhere in this potential. So the result is that the mass of these particles is very sensitive to the distance at which I measure them. And and for particle physics units, one is actually quite a small mass. And if it were in fact quite dramatically sensitive to the distance, it's very unnatural to be so small. Based on order of magnitude estimate, you would actually expected to be 17 orders of magnitude bigger. So the natural size would be more the Planck. Such plans to have 10 to the 19 GB, rather than the 10 to the two G.V. that it actually is as a question. When you say the mass. The point is it cannot be quadratic because it would be a good one, just one distance, and if you change this in a little bit, it would be completely different. And that's not what we observe. So this smallness of of this mass is not natural. We would expect it to be much, much bigger based on this type of argument. So we have to explain why nature can maintain the small mass of one hundred easy and simple. And that's the naturalness problem. Explain how the mass can be. Hundreds of small and supersymmetry provides a solution to this problem. How does it work? Well, it works bec
ause the coefficient there was this alpha coefficient. It was this number in front that says, how was the coefficient of this r squared in supersymmetric theories? The original standard model particles and their super partners contribute exactly the same amount, but with opposite signs to this alpha. So if as if I'm not only electrons and positrons popping out of the vacuum, but as well so electrons and positrons are that effect cancels and there's a zero in front of this r squared. So this quadratic running of the mass of the W and Z bosons goes away for exactly supersymmetric theories because in supersymmetry, the effect of the different types cancel. So that would be an explanation of the naturalness and well of the smallness of the size and the naturalness would be saved if this if nature would have, in addition to electrons and positrons, their superpowers. Well, that that would be too nice to be true because supersymmetry predicts that besides the spin on the other properties of the partner particles, so the selections for the electrons are actually the same. So in particular, I would predict that the electron also has the same mass as the Electron 511 K.V.. But of course, I told you nobody has seen this supersymmetric partner particle in particular. We would have known if there were a boson, so that could be a part in the particle at five hundred twelve. Sorry, I'm on the same question. 11. Now it's Typhon. 11 This, too, is wrong. So if there would be another particle with the same mass as the electron, I mean, we produce electrons all the all the time, and we have never produced any of these foreign particles. So so that that cannot be true. I mean, supersymmetry that predicts the partner particles have the same mass must be wrong. And the way out is there's also a Higgs effect. So the symmetry breaking effect from the ball rolling away from the center that breaks supersymmetry. So supersymmetry is also a broken symmetry like this rotational symmetry in natu
re. But we have to do this in a way to preserve this naturalness that the supersymmetry brings. So how does that work? So, so there's some way to break Susy, like with the ball and then the super partners of of all the known particles can have larger mass than the known particles, and then the quadratic running is back because the canceling is not exact anymore, but only up to about the mass of the super partner. So up from that mass on there again, particles and super PACs, and then the cancelation kicks in again. Is that clear? So for masses below the mass of super fast, the super planets are invisible and there is quadratic running, but for higher energies or for higher masses where the super partners are, the cancelation effectively works again. So we would expect that the running happens. There is quadratic running, but only up to the mass. Of the super partners, and that means since the mass that we observe of the billions that bulldozers have 100 GV, if this explanation of natural naturalist works, then this would suggest that super partners also have masses in this range of 100 G.V.. OK, that was the point with the naturalness that was actually the strongest point for supersymmetry. There's another point called unification of cage interaction, so I explained what gauge interactions are gauge interactions are these things with rotations? And I told you are three in nature. There is the electromagnetic force, which is one, there's the weak force and there's the strong force. And we measured their values while this the we measured how strong actually what we measure is the electric charge, and that's a measure of how strong the electromagnetic field is. And so so this is actually a measure of the distance here. So we are here at long distances away. We measured the values of the three of the three charges here, here and here, and I told you we can compute the coefficient of this logarithmic running this beta. And so we can extrapolate from our distance scale to
 other distance scales are here. So I told you this log of Q, well, this is effectively a measure of the distance. Get a logarithm of the distance. So this gives you a straight line and you see that they're almost meet in the point. Well, not quite right. The intersection of the three lines is pretty close, but it's not in one point. So pretty close already. Quite surprising if you have three generals, straight lines, they their interactions are all over the place. But here they almost meet at the same point. But with supersymmetry, the coefficient is a little bit different because the supersymmetric partners contribute with supersymmetry. These lines happen to meet all the same points at some distance scale or some energy scale 60 10 to the 16. In this graph, all the charges happen to be the same, although at our distance 'cause they're very different. So how can this be? So the idea is that actually these are not three different forces, but that this is a single force that comes about from a rotation and an even higher dimensional space than the hyperspace I was showing with Han and Chewbacca. Because this braking mechanism, so now I have tried to draw the brake and say, here is the blue ball, but now in the sphere. And if the blue, if the blue ball sits here, then a rotation of the ball around the axis that goes through this point is still a symmetry of this configuration. So the original ball had rotations about three axes as a symmetry. But after I placed the ball here, there's still one axis where the symmetry remains and the rotation about the two other axes are broken. So by placing the ball here, I do not completely remove the symmetry, but I make it smaller. Symmetry only rotation about one axis rather than three axis is the rotation of this. So the idea is if I go back. So also here is the Higgs effect. So this is the mass of this additional Higgs particle. And then there are three independent remaining symmetries that after this point, become one big rot
ation group while this rotation group is actually rotation in a 10 dimensional space. Again, I cannot draw this, but that is the idea. So, so this is how this comes about that. The three lines meet in one point. They all come from the same symmetry, highest symmetry. But this is not the only indication of this higher symmetry. Actually, there are more. So this diagram is called a weight diagram. I'm going to explain this says all the particles that we know fit nicely into groups of particles that transform, according to this being our symmetry. So many people believe that this symmetry is actually a symmetry of nature. I mean, at high energies where the breaking of the symmetry is undone. And there are also the fact that the neutrinos have masses and that there are masses are roughly in the right range is also an indication that this thing is going on. And I showed you this unification. The meeting of the three lines and one point happens only with the supersymmetry without supersymmetry does not happen. It's ruled out by a current observation. So if you if you want this, you need supersymmetry. The next open problem that is solved by Susie comes from a completely different angle of physics so far, I've talked about particle physics. Now let's talk about astrophysics. This is a galaxy and we've I mean this picture from Hubble Space Telescope. And so as you know, the galaxy is actually a disk, and we're viewing this disk from almost from the sign here. This this one. So the this and this disk is rotating around an axis that is almost vertically in this picture. And now what you can do by using the Doppler effect, you can measure the rotation velocity of this disk because you know, when you when the ambulance comes towards you, the sound is higher in pitch than when it goes away from you. Everybody knows the fact called Doppler effect that also happens for light and from observing the frequency. Or if you like the color of the light of the stars here, you can determin
e the velocity at which these stars are coming towards us or moving away. So if this galaxy rotates, say this way, then the stars here are coming towards us and the stars here are moving away from us and this can be measured. Right. So are people observe this for many, many galaxies. And the other thing you can do is you can just look at the picture and kind of count how many stars are in this galaxy? Well, not you, but people can. People have no idea how many, how many stars in this galaxy, and they also have no idea how big the stars are because astronomers again from the color of the star can determine the mass of the star. So you can see you can actually determine the mass distribution in this galaxy from looking at how bright it is. And so astronomy, that's something that astronomers can do. And since the rotation is balanced so that the centrifugal force from the rotation is balancing the gravitational pull of all the other stars towards the center of the galaxy by computing how much mass there is, you know how strong the gravitational pull on, say, this star here, and that determines how fast it has to go around the center of the galaxy. So. So when I say that this disk is rotating, it doesn't mean that it's uniformly rotating so that the speed of rotation can depend on the radius. Like in the in the Solar System, the speed at which the planets fly around the Sun depends on the distance of the planets from from the star. So, uh, so stars orbit the center of the galaxy, and let's let's draw a diagram. I draw this rotation velocity v against the radius, the distance from the center of the galaxy. And I told you from estimating the mass in the galaxy, you can predict the velocity of the star, the velocity of the stars as a function of the radius. So that gives you a curve that roughly looks like this. And you can measure it using the Doppler effect and what you measure. Looks like this. So obviously, there's something wrong with your prediction. So it turns out,
 I mean, this is the true thing, and this was predicted on the mass that you see. So how can this be wrong? How can you be so wrong? Well, the only solution is that you're not seeing all the mass. Actually, you need more than five times of the mass of the stars that you see in the galaxy to get this rotation curve. So this curve of velocities that is almost flat rather than decaying like this. So the conclusion is there must be more mass in this galaxy than the mass of the of the atoms in the stars. And further, from looking at the details of this curve, you can determine what this mass properties of where the smallest comes about. So you have to people conclude that this mass has to be in the form of heavy, stable particles so that are only subject to gravity and the weak force, but not electrically charged, all strongly interacting because so high, so heavy. It means that they are moving slowly. They are moving at relativistic speeds that move much slower than the speed of light in this galaxy. Furthermore, they must go through the stars and everything that happens in the galaxy without interacting with them without scattering with them, because otherwise they would also be kind of aligned with the stars and they are not aligned with the stars. And so that determines these the properties of this particle. So there has to be there has to be. And of course, it has to be stable because these galaxies have been around for a long, long time and they wouldn't be there anymore if these particles that make up this additional mass would have decayed in the meantime. So. So there has to be have is a heavy particle that is stable and not interacting, not not having any significant interaction with the matter of the stars. And such are such particles called the WIMP weakly interacting massive particle. And I should say no WIMPs are among the known species of particles. So in the standard model, there is no particle that that would work as a wimp first. Some of them are not he
avy enough, like the neutrinos would be wonderful WIMPs, except that they are much too light and the heavier particles wouldn't be kind of non-interactive with the stars. So there has to be an additional particle that makes up this dark matter in the galaxy. And it turns out supersymmetry provides exactly such a particle because of the following reason. So far, I haven't told you about this, but supersymmetric particles have a property called all parity. Parity is something that can be either +1 or minus one, and it's +1 for all the known particles and minus one for all the particle, the super partners that would have still be to be found and and that is conserved. So the product of this party? In a particle interaction has to be conserved, and that means you can only create new particles in pairs because the square. So each one would contribute a factor of minus one. So that's plus one. So here. So this is a process that you have to read from left to right, there are two quarks interacting giving a W boson and that decays now into these guys a supersymmetric partners and decays into two each. One having minus one is our party. And then these decay further. So this one decays by emitting a new neutrino. That's an ordinary particle. So and decay, there has to be an odd number of new particles in the product so that here there's one. There's a slept on and that again sends out an electron and there's also a remaining supersymmetric partner particle. So, so when they're created that created in pairs and when they decay. If there is a supersymmetric partner particle in a decade before the decay, that has to be one after the decay. So the total number of super partners in the process always has to be an even number. And that means if I have a super partner and it decays it all the products, there's always another super partner. And if I have the lightest super partner called the LSP the lightest supersymmetric particle, it cannot decay any further because there is no mas
s, no energy it can decay into, and it cannot decay into only stanozolol modeling particles because that would violate this parity. So that makes the light super partner stable and therefore such a LSP lightest supersymmetric particle has accepted the properties that we need to explain the dark matter and the rotation of galaxies. So that's another probe of supersymmetry. And finally, again, something close to my heart. I'm not going to say anything about this. That's we are not stuck with particles. There's also super strings. And if you ever want to make a realistic model out of super strings, that gives you a standard model particles their own. The only way we know to do this is also to actually create the super symmetric version of the standard model, but I'm not going to say anything more about this. So super strings also want supersymmetry. OK, so these five problems out of which I try to explain, three are all reason to believe that supersymmetry is actually a good idea to have. So let's look for it. And then what we look for. So that is and there's unfortunately a problem and particularly the breaking of the super symmetry. Remember, we needed to break it because we need the super partners to be heavy. It comes that's not in the 120 parameters to 120 numeric parameters. You should compare this to the 19 parameters that we have in the standard. So again, there's not the standard model, but there is a 19 dimensional space of standard models. You can you have to to choose 90 numbers. Here I've listed the ones of the standard model, so you have to choose the mass of the electron, the mass of the other particles you have to. There are some mixing angles, blah blah. In total, there are 19 numbers that you have to measure. These 90 numbers determine the standard model. Unfortunately for supersymmetry, you need to measure how many parameters to determine exactly which incarnation of the super symmetric of the minimum supersymmetric started when you have. So if you m
easure something, for example, of LHC after his speed spits it, well, first you would have to measure these how many parameters or you make an assumption about the the values of these parameters, and then you check whether that's realized or not. So you can turn this argument around and say that is with how many parameters there's plenty of room to avoid detection. So if you don't see anything, you say, Oh, maybe the pyramids have different values and you can go on, and every measurement that you make is relative to some choices for some or at least some of these parameters. So, so looking for supersymmetry is actually a hard thing because you have to determine a lot of numbers. And our best way to look for it for supersymmetry is at the Large Hadron Collider at CERN in Geneva. So, yeah, I gave you the picture that I hope you've seen many times before in the popular press. This is the collider ring somewhere here. This is the computing center or the control center on on the CERN ground, but they're at several points in the ring there. Detectors were actually experiments of and in particular, there are two of them here CMS and here Atlas are big detectors where the two beams that are running that are running around in the pipe here are we're colliding. So yesterday there was a talk about LHC that I hope explained this in much more detail than I can. So this for the for today, this all you have to know two detectors called Atlas and CMS that are different, but in principle, measuring the same thing. And there's another problem with the Large Hadron Collider, and that's harder on hydrogen. This is a type of particle and protons are examples of hadrons and protons, but none of these other things in the nucleus of an atom. These are the things that are accelerated at LHC because they're easy to accelerate to say it, in short. The problem is, remember, in my list of particles, there were no protons because they are not elementary. They consist of quarks, they consist of t
hree quarks. And actually because of this ring normalization effect and particles popping out of the vacuum. And these energies that we're looking at, they're actually of more or less 2000 particles. So a proton is a cloud of two thousand particles, including the ones that are popping out from the vacuum that you are accelerating and then you collide them. And when you collide two protons at LHC, you're not colliding to protons, but actually you pick from from the from each proton and pick one of these two thousand particles and you collide these two, these two particles and all the twice one thousand nine hundred ninety nine roughly particles just fly through as bystanders. And that makes this process. So that's a depiction of such collision. Very hard to analyze because there's a lot of garbage flying around. Also, these collisions happen while the the the beams have have a collision energy of 8V. But the 8V is distributed among these twice 20 particles, so the collision happens only with a small fraction of these 8V. And we don't know which fraction because we don't know the details of the particles. So we have to look at lots of these processes. Get rid of the DBRS and do statistical analysis on this, and that's actually quite hard. So it's not something you turn on. You see immediately see something. So that's a picture of of this atlas detector. You see a person that gives you an idea how big this thing is. This is a well, I mean, this is from the construction of of the detector. This is the detector with the inner part of the detector. Remove you. You look along the beam pipe here. This stuff is actually this empty space is actually filled with detector. This is only the outer part of the detector. And here you see the beam part like this, and this is part of the detector, the mean detector. So to get an idea of how big this is, so this is a multi-story building. If you be there several stories underground and this is what this detector measures are. Actually
, this is a simulation. What you see here, the beam pipe goes here in the middle. So some one beam of protons comes from here. The other beam of product comes from here and here they're supposed to collide. And when they collide, they go through several shells of detectors and the innermost shell. This consists of of a detector type where you can track the particles and the next shell. There, you can only see the energy that is deposited in the detector and that's indicated by these yellow bars. And then some particles named the muons make only those make it out of this initial of the detector and reach the outer part, and there again tracks where it can detect them. This is how one such collision looks like, and there are millions and millions of those every second. So this is what you're seeing are now. What would super symmetry look like? And the answer is the smoking gun for supersymmetry is that you don't see it in which sense, well, I explain to you that the LSP, the lightest supersymmetric particle, doesn't interact with matter, so it's invisible to the detector. It just flies out of the detector and you don't see it. You only see the rest of the particles, but you see that the remaining particles seem to violate momentum conservation and momentum conservation. This view is hard to determine because see, there is no detector along the beam pipes, so most of the stuff just flies in. Still, in the compartment is not detected, but if you view the detector head on, so now this is again looking along the beam pipe, you see that here is stuff going here. Is stuff going on here, stuff going. But everything is a little bit more to the right than to the left. There's nothing to the left. And both of them are to the right. So since the beam has no momentum transfers to the beam. This means in this collision, there must have been something that went this way with lots of energy to balance the tendency of all the rats to go to the right. So this means here some particle 
has been created that we don't see, and this is what supersymmetry would look look like. You would see an imbalance of energy. So this is what this is. The. We are looking for and there are some other more subtle effects that also indicate supersymmetry, and our expectation for LHC was I remember a couple of years ago before the LHC was turned on, I heard talks that said all within actually five minutes. If not, then in a week we discover supersymmetry. That was the expectation of particle physicist for the LHC. But when it was actually turned on and I actually was going, even the Fuhrer had to land. And we have not seen any direct evidence for supersymmetry at LHC, although we expected to see it there. So in a more technical way, these are this is actually a picture from from publication, from this one, from the steam detector. This is what they publish about supersymmetry. These are bounds that you're supposed to read like this. This is an enormous scale and energy scale, and these are all types of different supersymmetric partner particles that and also different processes in which they would would have been created. And you're supposed to read this as if super points exist. They have to be heavier than bluh in order that we wouldn't have seen them so far. So all these are so-called mass bound. So you see that the super partners would be have to be heavier while depending on the type and the process, then these numbers and I explain in the beginning that we would have expected them at 100 GB, which is here. So there's obviously a problem. So now what? As you know, there are known unknowns and unknown unknowns, as this famous philosopher explained. So what can we do? So I mean the easy, the easy way to wiggle out to say this, to say, Oh, there's still room in the parameter space. We can tune some of the under-20 parameters in such a way that that are compatible with the bounds that we obtained from the experiments. The other possibility is to say, Well, maybe this
 was only the simplest version. I accept this is the minimal supersymmetric version. We can also come up with extra stuff, even more particles, and in these more contrived models, again, there's even more wiggle room to say, Well, this could explain why we haven't seen it so far. But of course, these more complicated models are more baroque and even harder to well motivated. Or simply the high-energy v scale supersymmetry that would have explained Naturalis is not in its nature, a solution to naturalness. And but then so do we have to forget Suzy? Well, maybe not. But if Susy is not realized in nature and these solutions to look for some other regions parameter space, this would mean would have to come up with new solutions to these five problems that Suzy is actually solving for us. And I have to say not any good alternative candidate here is known. There are some for naturalness, but there there are even weaker physiological basis than supersymmetry. So my take-home message is, are I trying to explain that supersymmetry offers solutions to some of the most pressing open questions in particle physics? But unfortunately, it's not as easy as we had hoped. We haven't seen it, although we expected. But there's hope for the next round of LHC. Currently, LHC is not running. It's while people put in more stuff to make it run at even higher energies and higher collision rates. So we hope that within version two of LHC, more collisions at higher energy that those reveals supersymmetry and if not, then we have to come up with other ideas. So thanks for lot. So we have we have about 10, 10 minutes here for questions if you have any questions, if you can use the two microphones in the in the two aisles and I'll go form two neat, neat lines. And we'll start with this gentleman here and then work one two one two. So you said that the WIMP candidates would have to interact weekly as well, but at most weekly at most weekly? Yes. If oh, so it's possible that they would not partake 
in the week interaction because I was thinking that you have some events in the universe, which are very extreme manifestations of the weak interactions like supernovae where you get an enormous number of neutrinos and enormous densities of neutrinos. And if if we should not expect some sort of effect between WIMPs and neutrinos from a supernova, which would be observable well, whether they have to partake in some interaction, otherwise we couldn't. We could never create those particles. So that's the first thing. And then you are mixing things up. So indeed, a supernova is a very big energy concept. But the when I said these are high energies, even this 10 to the 19 TV Planck scale this as a mass from every day scale that's mg microgram now. So I mean, me doing this is a much higher energy process than any any plunks go process. The problem is when I do this, I'm not a single particle, but by that consists of two 10 to the twenty three particles and they share this energy and again, a supernova. I mean, that's a whole star exploding. So yes, it has much, much higher energy, but distributed among all the particles that make up the star. So yes and no, thanks. Well, it's actually the question. This gentleman over here. OK. And my question is, if there are such particles which do not interact electromagnetically with other parts but have mass? Shouldn't they concentrate in the center of a galaxy and change again? The rotation a little bit. No, no. Because of momentum conservation. They just fly. I mean, they don't. They only feel the mass. They just fly around on on big orbits. Nothing kind of. There's no friction that makes them fall into. So let me go back to my picture of the galaxy. No. Back, back, back, back, back, back, back, back, back, back, back, back, back, back, back, back. Here's my picture of a galaxy. The the fact that the galaxy is a disk comes actually from the friction. So it starts out. I mean, early in cosmic evolution, there was just stuff flying a
round. So it was more or less about three dimensional thing. But then it has rotation, so it has angular momentum. And because the stars, they actually feel each other. I mean, the stars, I mean, they interact gravitationally and they're heavy enough to have significant gravitational force. This complicated gravitational pull of all the millions of stars among them that acts like friction and that this friction makes this three dimensional bulb kind of decay and fall back. And the fact that there's angular momentum that has to be conserved that cannot be radiated off makes it actually go into a disk because the disk is the configuration with the given angle, the momentum of the kind of lowest, lowest energy. So if they don't retract they, they don't do this. They don't have the friction. They would just fly around and orbits like they're used to, you say. Gravity is not enough to build those concentrations. No, these because these are again, single particles. I mean, they're they're tiny, tiny particles. These are star stars have significant gravity. But these particles? And shouldn't those supersymmetric particles have affect to the HAWKINS' radiation if they constantly? So if you have it in the in the I mean, hawking radiation we look at, it sounds like this particular question needs to be taken. OK, so let's go. We'll take one answer is no, no hawking radiation. This is you. Remind me of my old physics teacher at university. No, you're wrong. We'll take questions here from the VÉCU here. It's up to you. It's my it's not my phone on. I don't know about. You just want to come forward to this. No. No, it works. Works, OK? I always thought the advantage of the LHC is that we accelerate protons. And now you say, well, proton is free quarks and a speck of dust on the actual collision takes place between only a small part of them. So why didn't you establish the electrons in the first place and accumulate all the energy to this one, lepton? Well, that was my first poin
t that was encoded in my answer. It's that easy to accelerate. Well, you can see you. Well, the problem is you want to accelerate them in the ring. And the fact that so people did that with the electrons in the past, the predecessor left, did this with electrons. But the electrons, when you put them on a circular orbit, they radiate off electromagnetic waves, they lose energy. Also, when you pull them on the ring and they lose more energy than you pump in by the acceleration. So if you want to accelerate electrons at these high energies that cannot do this in a ring, have to do this in a straight accelerator called Linear Accelerate. And actually, the next thing that physicists would like to build is such a linear accelerator that would be like 30 km pipes, straight pipes colliding. Actually, there was a proposal to build one here at DC, so that would have reach from pin it back. I am torn to the DC area in Bonn and then another 15 kilometers in the other direction. Not small. This gentleman here? Yeah. In the diagram that is just like next slide. So you? Yeah. Next one. Yeah, this one, you just show like an interaction with like supersymmetry particle and you see that there is like a neutrino like ejected on the top. Yeah, but couldn't we like see those neutrinos who like, detect them somehow? No, we don't see them as well. OK, so they haven't been seen or like. Well, I mean, not in a particle and not in such a particle detector. They are detectors for neutrinos, but they are completely, completely different. Yeah. No, I don't. But we could like have like some somewhere in the Earth, and we would like to see them coming from like those points in the galaxy or somewhere. So like seeing an excess of neutrino? Yeah. But. Remember, you're creating just one. Yeah. Compared to like the song, it's enough to detect you. Yeah, yeah. OK, so we're just about out of time here. Do we have any questions from the internet? No. OK. Maybe this lady in the back. Yeah, OK. We'll take
 one more here for this lady, and then I'll call it quits. OK, I have no clue, and I tried to get a basic understanding of this dark matter concept. So as I understood it, it had there should be mass. But this there is nothing that emits anything that we could measure. Is that right? Well, that we see, I mean, we just see light. So we only see stuff that emits light, namely stars. OK, what is light? Oh, that's a complicated light. So light. I mean, when you look at it, I mean, go outside. No clouds stars. You see the light from the stars. So that's what we see. I mean, that's our information about the galaxy, the light from the stars that reaches us. And this comes from stars and we know what stars are made out of. OK, so it's only light. Yeah, OK. OK, thanks. OK. Was that do you feel appropriately enlightened, come to me afterwards, and maybe I can give you a longer version of the Sense, OK? Well, this if there are any further questions, Dr. Helling will take up cheerfully. Take your questions in the lounge so I can place it. No, that's too loud. That's a lot. I just thought that all this probably also neatly explains why I failed. Q Can I try to find out? About 20 some odd years ago, it was embarrassing. Thank you very much. They can't focus, please.