 I'm Prem Paul. I have the honor and pleasure of being Vice Chancellor for Research and Economic Development. And I'm so pleased to see all of you here today. Because I think it is really critical to have a great audience for a great presentation. My job this afternoon is to introduce our legendary Chancellor. Harvey Perlman became UNL's 19th Chancellor 14 years ago. He, last week, he previously served as Dean of the University of Nebraska College of Law and is a proud alumnus of UNL. And of course, he drifted a little bit to a few universities and came home. During the past 14 years, he has provided tremendous leadership. And more importantly, he's provided an environment for faculty, students, and staff to excel. Isn't that wonderful? And I think that this is really what we are talking about in Nebraska lectures when we showcase our faculty's scholarly activity, their accomplishments. And that, Harvey has made that happen. Although he announced that he's going to step down after next year, we're excited about the next year and know that it will be one of the record books. I think it's already, his tenure is already in the record books, but next year will be even greater. We're so pleased that he's here today to introduce today's future speaker. So please join me in welcoming our legendary chancellor, Harvey Perlman. Well, thanks, Prem. One of the reasons that I'm happy to help sponsor this event is to showcase our faculty. And one of the reasons I'm happy to come is twice a year I get to hear Prem introduce me. It builds my ego and serves as a counterweight to the other things that happened during the rest of the year. But I want to welcome and thank you for joining us for the spring Nebraska lecture, the first of 2015. Today's lecture is being web streamed live. So I also want to welcome those of you who are joining us on the web. For those of you who use social media, the Twitter hashtag for today's lecture is hashtag NEB Lecture. We'd like also to extend a special welcome to a few of our guests. I'm especially delighted to have a group of students from Ashland Greenwood High School in our audience today. Please join me in giving them a big red welcome and hope that they'll all come back to UNL. The Nebraska Lectures are an interdisciplinary lecture series designed to foster communications among students and faculty in different academic areas and among citizens of Lincoln and Nebraska. These lectures are sponsored by the UNL Research Council in cooperation with the Office of the Chancellor, the Office of Research and Economic Development, and the Osher Lifelong Learning Institute known as ALI. I'd like to welcome any ALI members who have joined us today. The research council is composed of faculty from across many disciplines. Council solicits nominations of faculty for Nebraska lectures on the basis of major recent accomplishments and the lecturer's ability to explain their work. Selection as a Nebraska lecturer is the highest recognition the council can bestow on an individual faculty member. A few words about today's format. Following our lecture, Dr. Robert Powers, Vice Chair of the Research Council, Professor of Chemistry, will moderate a question and answer session before we conclude. And then following that, join us for a reception in the Heritage Room across the hall. Now it's my pleasure to introduce our speaker today, Dr. Dan Klase, Professor and Chair of our Department of Physics and Astronomy. Today's topic, what the heck is a Higgs boson, is remarkably timely. The Large Hadron Collider, which enables an international team of researchers to confirm the Higgs boson in 2012, relaunched last weekend at the CERN Laboratory in Switzerland. Finding evidence of the Higgs boson is one of the greatest scientific accomplishments of this century. The Higgs boson is often called the God Particle because of its potential to explain the existence of matter. Scientists around the world, including those here at UNL, anticipate even more discoveries during this latest round of atom smashing. UNL is fortunate to have a world-class high-energy physics team. Today's speaker is one of the physicists who worked on experiments involving the Large Hadron Collider. He and his UNL colleagues work on the compact muon solenoid particle detector that enables scientists to search for dark matter. In today's lecture, we'll learn about the much-studied Higgs boson. While the Higgs search has been widely publicized, it's little understood by those of us who are not particle physicists. We'll hear about a major collaboration between UNL and the National Science Foundation to make the compact muon solenoid more sensitive. Our university is also home to the Holland Computing Center, which is helping to capture and store the data from this experiment. As you can imagine, the amount of raw data is massive. Dr. Klays will examine how UNL physicists and the Holland Center are helping scientists worldwide use the giant data sets generated by these experiments. Dr. Klays holds a bachelor's degree from the University of Northern Iowa, PhD from Northwestern University. He was a post-doc research associate at SUNY Stony Brook before joining the UNL faculty in 1996. In addition to his expertise as a physicist, he's known for his talent in explaining high-level physics in terms that non-scientists can understand. We're fortunate to have him here for the Nebraska lecture speaker, and we are especially pleased to have his parents and family in the audience today. So please join me in welcoming Dr. Dan Klays. Thank you, Harvey. Thank you, Prem. I'll be saying those words again a little bit later in the talk. Who remembers exactly where they were when the European Center for Nuclear Research made that big announcement about the Higgs boson? Except for the handful of colleagues here. Most of you were asleep. It happened, after all, in Geneva, Switzerland time. But here's what you missed. That's Joe Nkondela, physics professor from the University of California, Santa Barbara, and spokesperson for the CMS experiment, updating everyone on the latest break in the analysis. And there's the response. That's Peter Higgs, the theorist for whom the particle is named, clearly a highly emotional moment for him. Whether you watched this live or just follow the Twitter feeds and blogs in newspaper or consulate, or you probably shared the frustration of the reporters that were there that kept asking, could somebody please, in a couple of sentences, in plain simple language, tell us what a Higgs boson is? Because it became clear that the honest answer to that query was, sorry, no. Which is why I've titled today's talk what the heck is a Higgs boson? We've all heard the short answer. The Higgs boson explains where mass comes from. Really. Where does mass come from? That's a thing that scientists asked. Because frankly, among the family, friends, neighbors that I'm accountable to, that is like the stupidest question anybody could ask. Where does mass come from? Mass is everywhere. It surrounds us. It inhabits everything that there is, the very air that we breathe, the ground we stand upon. If we weather the solid rock beneath our feet to grains as fine as you please, each and every individual, one of those of course, has mass all the way down to the very atoms that comprise it. The protons, the neutrons, the electrons, each of them have mass, so of course everything made out of them will. Problem solved. Case closed. That wasn't so tough, was it? Clearly, the question that physicists were trying to answer was more subtle than that. If mass is a defining characteristic along with charge and spin and identifying the fundamental building blocks of nature, we could ask the question, why does each one display the mass that it does? You may not know, recognize the particles that are listed here, with one at the top, you should. The electron, two convenient units, will use the electron volts on the far right. Why does an electron have half a million electron volts worth of mass? Or reading down the list, up corks, strange corks, muon pine, proton. Why does the proton have 938 million electron volts worth of mass? Why does each fundamental particle have that characteristic defining unit of mass? But more perplexing, why are there some particles like the photon that have absolutely no mass at all? Just knowing the particles of which the universe is comprised doesn't tell the whole story. To understand how fundamental particles form atoms and the atoms eventually build up an entire universe, we need to understand the way they interact with one another. Particles stake out their territory and communicate their presence to one another by constantly exchanging messages back and forth. Not unlike a remote control device, sends a pulsed signal to a receiver. Inside such a device, there's usually a small antenna, current driven to oscillate ups and down, produces a pulse of light. Could be microwave, could be radio wave, could be infrared. But that pulse of wave then is incident upon the passive electrons in some antenna that start them flowing in the current. That message sent for one electron through space to another works because it's based on the principle it merely exploits a very fundamental microscopic process that happens. The light that I described being transmitted between, we ordinarily think of light from a lamp as bathing us in a soft continuous uniform smooth glow. But actually, like the air we breathe, water around us, we appreciate those are grainy. They're made up of tiny atoms. Well, so is light. Light is made out of tiny pulses of energy we call photons. You may remember that from high school chemistry, where you'll learn that at least the light that comes from gas discharge tubes like a neon lamp or a mercury vapor lamp, those work because excited electrons, atomic electrons, falling to the ground state lose energy as they drop and they shed that energy by ejecting light at a characteristic frequency. That's clear when we look at the spectra of such light. We don't see a continuous rainbow of color but isolated individual lines of color that provide essentially fingerprints by which we can identify what particular element is glowing. These are diagrams that were created by Richard Feynman to describe the fundamental processes that take place in his theory of quantum electrodynamics. On the left, those first two diagrams are simply a summary of what I've just described. There's an electron making a transition and shedding a photon of light, particle of light. Here is light incident upon and being absorbed by an electron which gains energy in the process. Now here are two more diagrams from the theory. You can think of them as having been created by taking the diagrams on the left, grabbing any of the lines that represent the trajectory of a particle and cranking them around to a new position. For example, whoops, grabbing this electron leg, cranking it to the other side so it looks like this. But we've got to respect a little bit of algebra in the process. I can read this as an equation from left to right. It started off with an electron, end up with an electron that has given up energy and shed a photon. Moving a term in algebra from one side of the equation to the other, you've got to subtract it, right? The equivalent argument here is I move trajectory legs from one side of the diagram to the other by adding their opposite. And the opposite of an electron, negative electron, is a positive anti-electron. The diagram on the upper right tells the story of matter and antimatter, electron and anti-electron, meeting and annihilating, and what survives is a burst of light, a photon of energy. And on the lower right, there is a high energy photon that splits into a matter anti-pair, both of these processes on the right are ubiquitous in nature, they actually happen. We in fact can provoke and manipulate them in high energy experiments, and we do that all of the time. So, nature is made up, so notice even this diagram, I can describe how one electron can be aware of the presence of another, can be repelled by another, can be disturbed by another, even if they don't touch directly. One transmits, excuse me, one transmits an electron that the other one picks up. Electrons feel one another through the photons that they exchange. The world that we observe is built out of a class of particles called fermions, and you know a couple of them. There are two types of fermions, there are the light ones, and then we'll talk about the heavier ones in the moment, the light ones are represented by the electron. Leptons, light fermions, are the electron and there are others, there's the neutrino and the muon, and the other class of fermions are quarks. Up and down quarks in combination actually make protons and neutrons. Leptons and quarks are both, remember, fermions. And the fermions know about one another by emitting and absorbing bosons. The photon that I talked about being exchanged between electrons is an example of a boson. The photon, the particle of light is a boson. This mechanism is repeated frequently in nature. Besides electrons emitting photons, think of the transmitting antenna producing radio waves, electrons making light. Quarks can shed another kind of boson, the gluon. It's the exchange of gluons that bind quarks together in the protons and the neutrons. There's another boson, there's a class of bosons, the weakons, the W and Z bosons, exchanges of which mediate the weak force. And in that mediation, something remarkable happens, the leptons actually change their nature. Muons or electrons can be converted into neutrinos and down quarks into up quarks. In any case, we've got a world built out of fermions. All matter is made out of fermions. But the forces between them are exchanged by bosons like the photon. That would tell the tale, the standard model of physics were not for a very interesting and peculiar fact about the subatomic world. If a spray of solid particles were fired toward a barrier with a small aperture in it, like these machine gun bullets fired at an armored plate with a small opening hole in it and aperture there, we'd collect on the far screen to the right a clump that would represent perhaps something like this image, a tightly distributed set of target marks that is fixed by the size and shape of the hole through which the bullets pass. If I had two adjacent openings to pass through, then I would look for on the far screen a pair of collected bullet marks. But that exercise was recently done by an atomic physicist here, the University of Nebraska, Herman Botlon, who replaced the bullets with a low intensity electron beam. He targeted a window of silicon nitride in which had been milled two slits, each one about 10 atoms wide, 100 atoms apart, and parked behind it was a CCD camera. The pixel images that you see lighting up represent the real time receipt of electrons having passed through those slits, landing in the camera. We should be looking for, I guess, to slit shapes that would suggest the size and shape of the slits the electron passed through in reaching the camera, but we're seeing something quite different. In fact, it's so peculiar, it looks to me like we see electrons being collected in what we would expect to be the projected shadow between the slits. And I also see electrons being collected to the far left and right beyond the boundaries of the slit. I do see a pattern, though. You see that? I see blobs, I just don't see two blobs. I see lots of them. Let's step back from this image and note that we were focused in very tightly on an overall pattern of many spots. This doesn't look like a collection of solid particles passing through a couple of openings. This looks reminiscent of what we expect from wave interference. You know, in the kitchen, microwaves, when they encounter their own reflections off the wall of the chamber, can interfere into spots of high and low intensity. They correspond to the cold spots in the burrito you heated up. You try to correct by having a rotating platform to fix it. Here, sources of ripples on the top of a pond, if you look at it on edge, you also see this sort of pattern being produced. And this is the pattern of visible laser light being passed through two narrow, close together slits. The pattern you see is unmistakable. It looks exactly like what we collected with that CCD camera for the electrons. And remember, these are photons of light, little wave-like pellets of light. Just some more evidence. Top picture is once again, electrons passing through a couple of narrow apertures. At the bottom, electrons being simply reflected off of a single crystal. In both cases, you see a spectacular display of beautiful symmetric patterns. The electrons are acting as if they're waves. This, by the way, was first predicted in 1924 by De Broglie. He won the 1929 Nobel Prize for it after it was demonstrated to be true in 1927 by Davidson and Germer. So Hermann Bartlein didn't discover this, but he found a novel way of using new technology to display it. That was awfully cool. This means at the subatomic level, we've got to treat things like electrons as if they were waves. And the equations we use will describe them as little concentrated wave packets. And that means the collision of particles off one another at that level should be understood in terms of the reflections of waves off of energy barriers. In quantum mechanics, in Schrodinger's equation from quantum mechanics, we treat the electron as if it were a small packet of wave, little standing wave pattern of energy. But wait a minute. That's what a photon is, right? Photon is just a wave packet of energy. And yet, they're different. One has mass, the other doesn't. It forces us, when we use Schrodinger's equation, to introduce into the equation a mass term for the electron that we totally ignore for the photon. That's not a theoretically inspired or driven motivation for adding the term. That's just a fix to the equation done at Hock. Why should two things that are best described as wave patterns of energy, how can one have mass and the other one doesn't? The solution that was suggested was yet another boson. But unlike the bosons that I've described so far, remember, fermions exchange bosons. This would be a boson that everything could play with. Not only will fermions exchange this new boson, but other bosons will be, will as well. This is a boson that can be exchanged by other bosons. Theory first floated and was fleshed out in the late, in the late 60s by a handful, about seven or eight theorists, although Peter Higgs, who you saw at the very beginning of the show, is the one whose name is most closely associated to it. Here's the basis of the theory. Every fundamental particle can emit or absorb Higgs in the same way that charged particles can emit or absorb photons of light. How readily, how easily, how strongly this association is, how readily these things shed and absorb Higgs gives us an impression of how massive they are. That gives the appearance of mass in a way I'll explain in a moment. But here you see across the top, two fermions having an exchange with a Higgs boson. The upper left hand an electron shedding a Higgs and the upper right a top anti top annihilating into a Higgs. But notice across the bottom I have these Feynman diagrams that show Z and W bosons, the weakens, exchanging Higgs particles. It's because the Z and the W can couple in this way to Higgs bosons that they have mass while the photon and the gluon do not. This Higgs particle being capable of being emitted and absorbed by bosons opens the door for the possibility for a Higgs to be able to generate other Higgs. Which is why the theory anticipated that the Higgs boson itself should have mass. It's the constant interruption of particles that would otherwise move freely through space interacting with the Higgs bosons that fill all of space. If all particles are emitting and absorbing Higgs all the time, all space is filled with them. And a particle that interacts heavily and frequently and readily and easily with Higgs will have a hard time passing through the space that has this sea of Higgs that surrounds it. Let's compare this barracuda streamlined enough that it knives through the water with very little drag compared to the lumbering oaf behind who sluggishly plods through the water. At the bottom, think an electron, something that appears light to us and behind it a W or a Z. Or if you prefer, think of a downhill skier gliding easily across the hard packed snow and others trying to navigate the same terrain perhaps in snowshoes or worse yet heavy boots while at the same time, some things can just glide effortlessly by above the fray. Photon, those Feynman diagrams that I argued meant all these fermions and bosons could exchange Higgs, could be monkey it around with and redesigned to argue that there should be a decay channel available to the Higgs boson which means if the Higgs boson were ever teased into existence by some high energy collision in a high energy experiment, there are many ways that it might decay which means the Higgs gotta be unstable. And in fact, simple probability and statistics would argue if there are many ways that it might decay, its lifetime must be very short. It was anticipated that the average lifetime of Higgs particle would be something like 0.21016 seconds. And at that rate of decay, we have no chance of ever observing a Higgs particle directly. We will only be able to infer its presence by the appearance of the particles into which it can decay. Now if the Higgs has many ways of decaying that has many channels that might decay, appreciate though that any particle that's gonna decay into a couple of daughter products must itself have been heavier than the particles that it ends up with, right? And it's any excess mass to begin with to end that gives it the energy for those particles to fly apart. This Higgs interacting most readily with those particles that we perceive as the most massive suggests that the Higgs would preferentially decay into the heaviest available particles to it. Those would be the W and Z bosons. And on this plot where I've plotted Higgs mass, it's just to remind you that before it was discovered we had no clue of what the Higgs mass actually was. If it were massive enough, say 180 or 200 GeV, then it could easily decay into a pair of Ws or a pair of Zs. This is a plot of from one and fractions thereof, the preponderance of the decays that would be expected. On the far right, if we were heavy enough, we decay almost exclusively to a pair of Ws or a pair of Zs and everything else is microscopically contributing to the decay. On the other hand, if the Higgs actually were too light to decay into a pair of Ws, then it would have to go down the laundry list of things it couples to and decay, in this case, predominantly if it were about 100 GeV to a BB bar quark anti-quark pair or Tows or Gammas or something else. And in between it's sort of split. These are the relative strengths of the intensity of or frequency of each of these decays predicted before we knew its mass but suggesting to us we had to look everywhere for it. It could decay into almost anything. And the problem is most of the stuff that it might decay into, Ws, Muons, Tows, B quarks, Charm, those are common in the debris created by the collisions in a high-energy experiment. And complicated by the fact that most of these collisions have so many particles spraying out. If there was a Higgs buried in there, that decayed into a pair of particles, how are you supposed to even tell? Well, this is how we tried. The CMS detector is one of the largest instruments man has ever built. It's 14,000 tons, five stories tall, 75 feet long. It's buried 100 meters underground. It has a 100 million separate individual sensitive detector elements that are arrayed in panels next to each other, assembled in walls, stacked in layers to surround a collision point. That collision point underground is where are directed from opposite directions to pencil-led thin beams of protons traveling at close to the speed of light, which collide right at the center by design of the detector. Kapow! The detector itself is designed to be sensitive to the different characteristics of the particles it's meant to detect. Different fundamental particles, by virtue of the charge and mass, they react differently as they pass through material. Some petering out or ranging out sooner and others persisting deeper into the layers of the detector. The innermost part of the detector is the pixel tracker. And I'll talk a lot more about that in a moment. But the innermost layers are all like that CCD camera that was capturing the electrons. A bunch of little silicon pixels, about 100 by 150 micron square. Not much more than the width of a couple hairs from your head. Every time charged particles pass through one of those pixels, we know it. And we can identify charged particles by the signature energy that they leave deposited in each of the pixels they pass through. There's also a suggestion here by dashed lines of a couple of particles that are going through the tracker but leaving no signal. That's because those are supposed to represent uncharged or neutral particles. Photons and electrons peter out quickly when they enter into material. And that's why the innermost layer after the tracker is called the electromagnetic calorimeter. And depositions of energy will be collected for photons or electrons that strike it and sort of slow down and get break to a stop. We can distinguish photons from electrons because photons have no charge and leave no telltale track behind what electrons do. Most charged, most particles will be stopped at the next layer of the detector, the hedron calorimeter. So protons, neutrons, pions, caons, those will all come to a stop leaving their energy in that section. The hole inside here is surrounded by, these are the walls of a giant four Tesla magnet that allows the charged particles to curve and us to distinguish positive charge from negative charge. And by the radius of curvature, measure the momentum that each particle carries. What survives that? Well, muons are heavy particles that interact very weakly with material and they pass readily through our detector and survive to be picked up by tracking elements out here. So this would be a muon. And finally, neutrinos which are neutral, not charged at all, and interact so feebly that they usually just escape our detector without any signal left behind at all. We infer its existence by a telltale imbalance in the total energy measured by all the particles that we do see. If that's how we identify the fundamental particles that we know, how do we find the existence of a new particle? Especially a particle that doesn't exist long enough to survive to be detected and we only see its byproducts of its decay. Well, for the physics that we understand very well, like any phenomena you know well, you should be able to make predictions and anticipate what you'll find. Imagine a bucket full of 1,000 coins thrown into the air, each with one half probability of showing up ahead. If we count the number of heads when they finally all fall, we would expect on any single toss to get about 500 or something close to it. No guarantee but something close. This is a simulation of 1,000 trials of throwing 1,000 coins up at once. And you'll notice the central value near the peak is about at 500. And it's very rare that you're gonna see six or 700 heads or two or 300. Most of them clump around 500. If you ran this experiment and you saw something like that, you'd probably be highly suspicious that at least a handful of those coins were weighted. Or if the central value was off or the spread in the data looked all wrong, you'd be suspicious about the characteristics of every coin in the batch. This is how we look for new physics. We predict what we expect to see in the detector and look for deviations from it. This is CMS data of a collection of events and the measured missing transverse energy in the event. Remember it's the imbalance or missing energy that's evidence of neutrinos having escaped our detector. We know about a lot of processes that create neutrinos and we should be able to predict how often we see so many and what their distribution through the detector might be. And what all of these colors in the histograms are are the anticipated predicted contribution from known processes that generate neutrinos and the dots are the observed data. The fact that the data matches the predictions so beautifully is a testament to how well we understand the underlying physics that takes place and how well we understand the performance of our detector. For which it's significant if there's any error on the estimated position of these data points, they're suggested by the lines, the error bars. So where the statistics are low, there's significant error but not much up there. And in estimating the contributions from each of there there's any estimated error and those estimates, those are represented by the hatched regions there but I think you can see that certainly well within the error bars that the predictions beautifully align with the data. Here's another distribution, something called the invariant mass that I'll explain in a moment. It's a value calculate from all the stuff you see in the event. But once again I see the things that I think will contribute a certain amount across the spectrum to this calculation and then I see my data. In neither the previous case or this case do I see any suspicious deviations from what we expect. But should we, there's an almost surefire way if you collect enough statistics to know that you found a new particle. And that's because remember when I said particle can decay into daughters as long as it's originally more massive than the things it decays into. And the excess mass between this and the final states go into the energy that drive them apart. I can reverse that analysis and say if I've identified a couple of particles that I believe came from a decay by looking at their, identifying them and knowing their mass, measuring their energy, looking at things like the angle that separates them, I can work backwards and predict or reverse calculate what the mass of the parent that produced to them should be. I can collect data and look for pairs of objects in the data and make that calculation. If I indiscriminately take pairs of particles out of event after event after event after event and I try to calculate this so-called invariant mass of its parent, it's unlikely that by random choice I've found the pairs that did come from a parent and all likelihood they were unrelated, stray particles that weren't associated with the common parent and I just forced them into the equation. I got an answer, but the answer would be nonsense. I'd get answers all over the map. That's what you see in this plot. However, if buried in the data, or at least a handful of particles that actually were the decays of some particular parent, each and every time I'd perform the calculation for those pairings, I would reliably always get the same answer. That means if I collect enough statistics, even though I've picked a lot of random pairs that gave us this background, I'll unmistakably be able to tell that I had a certain number of particles that decayed from a parent with a precise mass. This is data, again from the CMS experiment, of a large collection of events that had at least two muons in them and we performed this calculation for every pairing of them. There's an enormous amount of background nonsense, but there's also unmistakable seven spikes. They correspond exactly to seven already well-known and established particles that do in fact decay to muons. Notice the largest one of here is a Z boson. It's just under 100 GeV. Large statistics runs, large statistic runs like collected here by the D0 experiment at Fermilab can make those spikes so well-defined that we can fit the data, find the central value, and know by a precise measurement the mass of that particle. At the CMS experiment, the first hint that we might have seen a Higgs came in data that looked like this. Selections were made on the data to try to drive down the otherwise overwhelming background so the amount of surviving data is small. So there's not many total events on this plot and as a consequence there's a lot of statistical scatter. But in blue and green are the predicted contributions to this invariant mass. Oh, it says four leptons. This was under an assumption that maybe the Higgs would decay to a pair of Zs and then each Z would decay to a pair of leptons, couple of electrons or a couple of muons. So these were paired together to calculate a mass and then these were paired together to calculate a mass. I see points above the predicted background, contributions of other processes. But judging by the air bars, I'm not sure that they're significant and you probably wouldn't try to convince anyone that you've discovered anything here. You shouldn't try. However, there's something tantalizing here in the data. There are four consecutive points that are above background. And if this is statistical random fluctuation then the likelihood of four in a row all fluctuating high is rather small. But again, you wouldn't wanna claim you discovered anything although interestingly enough in many analysis being performed at the time at CMS they were seeing the same sort of tiny little hint at about the same mass between 120 and 130 GeV. Our strongest signal, strongest evidence for the Higgs came in the gamma gamma or two photon channel, the decay of a Higgs to two photons. And this is a reconstruction of one of the events from the CMS experiment. Here is the data that first caused the excitement. Do you see it? Do you see the spike rising above the background? Probably not. The amount of background is enormous. And the number of Higgs admittedly in this picture is so small that statistical fluctuations almost make it impossible to see. Except, where did we think we might have seen something in that slide before? It was about at 125 and if I look above 125, ah, there is one data point, it's own error bars marked, the spread of error in the estimated background behind it and there's a sizable gap between the two. Okay, you'd be justified in insisting that we get more data before we say anything about this. When we double the data, we also did a couple of other things. We restricted ourselves to those portions of the detector most sensitive to photons and those range of photon energies that we can measure most precisely. Then we get this background, which was fit very smoothly with error estimates, the former hatched marks by these colored bands. And here we see three distinct points that are above the background and outside the error bars marked on each one. This was the summary that Joe and Candela was addressing at the beginning that caused the pandemonium that brought the house down. Since that time, with more data, the signal has grown only stronger. Here's the raw data up here, if you subtract out the background so it's across to flat zero here, you'll see, look at the scale, zero, 100, 200. There are several hundred Higgs in that peak. And fortunately, our competitive experiment, Atlas, sees the same peak at the same place for the same signal, pairs of gammas, pairs of photons. You know that first plot I showed with the ratty statistics that didn't look very promising? Here's how it looks now, released by the Atlas experiment. There's pretty clear evidence at 125 GeV of Higgs decaying to two Zs and the Zs decaying to leptons. This, by the way, is just the mass of the Z peak. Remember, that was just under 100 GeV and it's used to calibrate the rest of the measurements. This experiment is huge. There are 3,800 physicists, technicians, engineers working on CMS. I'm proud to be one of five faculty at the University of Nebraska that work on that experiment. Together with Greg Snow, Aaron Dominguez, Ilya Kravchenko and Kenneth Bloom, 3,800 physicists were a team of five that might seem daunting were not for the fact that the faculty here at the University of Nebraska have assumed major responsibilities on that experiment that have raised their own stature in that of the University of Nebraska. I'll talk about two particular things that are being done. First, I point out that we're joined by, we've got three postdocs that are working with us, five graduate students and about a dozen undergraduates working assorted projects associated with our work. This was a collection of us that just happened to be around the day a photographer was. I wanna talk about people that I'd been working closely with. My first graduate student was Carl Lundsted who at the time became probably the world's leading expert in jet pointing. Jets are collimated tight sprays of particles that are provoked by certain quark reactions inside the collision. These sprays are jets. He would extrapolate the tracks backwards and find their common origin and use that to diagnose perhaps problems with measuring the overall energy of the total particles in the jet. Carl still contributes to our effort but now as an administrator for one of the computer clusters that service the CERN experiment here at the University of Nebraska. I'll say more about that effort in a moment. Jason Keller was an expert in identifying jets whose origin were specifically be quarks. Jason's a recent graduate. He's now working for the National Opinion Research Corporation at the University of Chicago. And Suvidy Boyce is my postdoc stationed at Fermilab outside of Chicago. And his expertise is in the reconstruction of jets specifically looking for substructure in the particles that form the jet. That's something that can help us distinguish between single jets and two closely overlapping jets. Although he can also apply this information to tell us something about the origin of the interaction that created that jet as well. Gosh, it was 10 years ago that my colleagues Ken Bloom and Aaron Dominguez partnered with Computer Science and Engineering Professor David Swanson, now the director of the Holland Computing Center and secured a $2 million grant from the National Science Foundation to establish a large computer cluster here on campus. One that grew and eventually became an integral part of a worldwide system of distributed computing. This was all made possible by generous investments by the University of Nebraska Office of Research and Development, thank you Prem, thank you Harvey, in upgrading the connectivity of our university through the internet, made all of this stuff possible. Formally the athletic offices in South Stadium are repurposed as a shore computing center providing state of the art environmentally controlled rooms to house several computer clusters, one of which is dubbed red, it has 303,000 individual CPUs racked up for use. And that $2 million grant that was brought in, that was just the tip of the iceberg. Ken Bloom for about 10 years now has been the USCMS tier two project manager overseeing all seven US sites that have centers like the University of Nebraska has, but the University of Nebraska has the project manager for all seven of them. That's Wisconsin Purdue, Caltech, San Diego, Florida, Nebraska, MIT, Wisconsin. For the last five years, Ken has also served as the deputy level one manager of software and computing for the whole USCMS operations program. And just this January, congratulations Ken, he was promoted to manager of that same program and he oversees $18 million annual budget. A lot of that money funneled through the University of Nebraska. If you open up the CMS detector, gosh, it's beautiful, and you appear inside either half, you'll see where nestled in the center the tracking system sits itself an array of tiny little circuit boards that have on them something like the CCD cameras that were capturing those electrons in that movie clip I showed before. These are the pixel detectors. They're read out by circuit boards like this, designed, built, and tested here at the University of Nebraska. That's work that's done in a clean room where the fashion statement daily is this. Besides myself and Greg and Aaron, you see the trained technicians from our electronics shop, Bob and Brian, undergraduate Seth, graduate student Jose, all under the direction and supervision of our lab manager, Frank Meyer. These circuit boards are assembled through a robotic pick in place gantry being operated here by Seth and Jose, connected by delicate wire bonding, which is performed by an instrument we have here in the lab, the University of Nebraska, operated and demonstrated here by Frank. And my colleague, Aaron Dominguez, when he served as tracker deputy project manager, he spent a large fraction of his time for two or three years stationed at CERN overseeing the work of about 75 institutions that were contributing workers who at various times totaled up to 500 people in the installation and commissioning of the first tracking detector that saw service through the initial runs and is still being used in the CMS detector. Aaron also has a recent promotion to deputy project manager for USCMS phase one upgrades and as such is overseeing the R&D effort to eventually replace a lot of the guts of CMS in a couple of years. And just recently, he honchoed a big successful push to bring an $11.5 million grant to get that work done to the University of Nebraska. You've probably heard the news. Scant days ago, beam was injected again after a two-year hiatus of maintenance period at the lab. We've got beam circulating in the instrument again. It'll be a couple of weeks until it's tuned and ramped up to the optimal energy, which we hope will be twice what we ran it before. I want you to realize that the experiment here is not just a Higgs machine. This is a multi-purpose detector. The intention is to explore a large suite of questions, one of which we think we've got a handle on now. The origin of particle mass, the discovery of the predicted Higgs tells us we're on the right path for that. But there are a lot of other unanswered questions in physics. You probably asked when you saw that early slide, what in the heck are all those particles for? 96% of the universe is not those particles. What's dark matter? We're hoping to get a hint in the next run. Are there dimensions beyond those that our senses explore every day? And if the universe had its origin in the Big Bang, what happened to all of the antimatter? Since matter and antimatter should have been made in equal amounts. There are still some outstanding questions with this Higgs boson, is it? Honestly, the particle that Peter Higgs predicted. Remember, if it is, it has many ways that it should decay. Now that we've ascertained its mass at 125 GeV, look where we intercept these relative strengths of decay channels. Only two of which so far do we have direct evidence that the Higgs decays that way. If the real Higgs, we should be able to find it decaying to BB bar. We should be able to find it decaying to Tau's, to Charm, to pairs of Z's. Oh no, it's the Z we found, not the W's. And unless and if we do, it may be something different. I'm gonna stop there so that those that have questions can answer them and thank you for your time. So Daniel, thank you very much for a really exciting story and fascinating outcome. And I'm sure there are a number of questions. So if you do, please come up to the microphone in the center and pose your question. While we're waiting for someone to walk up, I do have a question that started with you. Okay. So during introduction, you mentioned that one of the bosons, the weak bonds was related to the weak force. So since the Higgs boson is related to mass, you think that's gonna lead any insight in terms of gravitational force since it's... So when I argued that the world of matter is made out of fermions, and that fermions feel one another through an exchange of bosons, we believe that also is the way gravity works. So gravity must be mediated by some boson. That's the graviton. The problem with trying to study gravitons in high energy collisions is we work at the subatomic level. And although we tend to think of gravity as being a pretty strong force, that's only because we encounter the gravity being created by the earth beneath our feet, which is an astronomically huge body. When you're down at the level of individual fundamental particles like in a high energy interaction, the force of gravity is too small to measure at all. So it's hard to do gravity experiments. One thing about the Higgs that I can point out, though, is that the source of gravity, we think of ordinarily as coming from mass, massive objects have gravity. Actually, gravity comes from the total energy of an object, which is its rest mass plus other forms, but light is deflected by gravity, which means you don't have to have mass to feel gravity. You just have to have energy. So gravity source is not necessarily mass, gravity source is total energy of a body. And so the Higgs mechanism is a little bit separate from gravity yet. We have not found a successful way to incorporate gravitational theories with the so-called standard model that I described. When you mentioned decay, I get the sense that there's time involved with that, with the variation with speeds and time warps, for lack of a better term. Would that influence where you're looking for the Higgs particles? So for... Are you getting to velocities? What is the velocity of these reactions shooting through the sensors? Is that speed of light? They are very, very close to the speed of light. So is there any situation where time would influence that? The fact that these particles are traveling close to the speed of light does mean there's some time warping, as you put it. You mentioned also about that perhaps we're in this pool of these Higgs, in my call, is particles correct term? Sure. Okay. And we also sometimes describe this sea of Higgs as a Higgs field. Okay, in this Higgs field, and the decay speed is so, I mean, quick. I mean, I'm trying to imagine this in my mind. Is it just something that's just there and gone, but there's new ones continually just being there and gone? So part of the story that I didn't describe, when I suggested that the light coming from a lamp is made up of these little pellets, the photons. There's another part of this quantum field theory that say around every electric charge, like an electron, like a proton, is a sea of photons. That they're continuously being given up and absorbed by their source. And only one another, say this is an electron. Another electron wanders close enough to encounter one of the sea of photons this thing is generating. Do they feel the repulsion of one another? So are there real photons there? Or are they, in a high school textbook, you probably saw this described as an electric field around the electron. There's an electric field that pushes away other electrons. But in the same way that I kind of suggested our image of what subatomic particles look like, are they particles or are they waves? Quantum mechanics blurs the distinction between those two. Quantum mechanics also blurs the distinction between fields, like the gravitational field around the earth or the electric field around a charge, between that field and the sea of particles that surround. Recognize the Faraday and then James Clerk Maxwell and all that weird stuff. All that weird stuff. But also, I lost my cat during an experiment, and but I can't help but to think about in this situation how this huge machine affects what you're looking for. I mean, and with that I'll finish, thank you. So he's posing the question, there's an argument, philosophical argument, that the result you see from a experiment, quantum mechanical experiment, can be affected by the way you design your experiment. But in particle physics, these collisions are very real and the tracks that we see left behind are unmistakable. And the kind of mind games that are explored in Schrodinger's cat that you alluded to, they are usually on time scales or physical space scales where something happens and before an observation can be made, it's undeterminate what really happened. But in the real world, as soon as anything that comes out of that event interacts with any other particle around it, that makes the decision for you. It isn't that you wait at this detector at large distances with 100 million elements and you wait until you get the data and analyze it, that you force an event to happen in the past. As soon as these particles interact with one another, they absolutely define the process that took place. And excellent presentation, very tough topic and trying to make it easier for us. I had the benefit of being at CERN. Aaron was there on sabbatical and providing leadership. So seeing firsthand and I've been fortunate to work with the high energy physics team ever since I've been here, I've been very impressed. And I think it's a really a wonderful case study that just a very small team and yet having a global impact and not just contributing to science but actually also providing leadership. So my question is that in an environment that collaborations are very difficult to start and achieve and maintain and yet be productive and yet high energy physics team has done. So looking back, what are the some of the lessons that your team has learned both positive and negative that might encourage us to replicate this experiment and multiply it into multiple areas? So we have the advantage in high energy that that's the culture. These experiments are large enough that they can't be performed without lots of institutions investing lots of manpower and resources. And probably other areas of science don't necessarily even think in terms of that level of collaboration. It's the scale of the experiment that fix it. So when you set your sights big, then you need that sort of help and cooperation. And you're all for big ideas all the time. So I think this thing is gonna naturally happen for a lot of our efforts as we push the envelope to do new stuff and exciting stuff. And thank you Prem again for the third time. So if there's no other questions, please join me in thanking Daniel again. But then what a wonderful presentation and but we have a tradition there that the face that everyone has been seeing on campus and everywhere for the last few months. Now we want to give you a framed copy of that poster. So now you can get sick of it, looking at it every day. Thank you very much. Thank you.