ATLAS and the LHC

about this very topic. Back in two thousand twelve, tech Stuff did an episode about the Large Hadron Collider and a lot has happened in those five years since that podcast, so I thought it would be good to revisit the topic. Plus, some of my coworkers had a chance to chat with some scientists from the LHC at mog Festen. I'm incredibly envious of that and I'm going to include some excerpts from those interviews in this episode, and they're pretty awesome.

So what is the Large Hadron Collider? What is this LHC thing? Well, what's a particle accelerator, which means it uses forces to accelerate subatomic particles two speeds approaching the speed of light. The LHC design allows for two streams to accelerate in opposite directions, each looping around the massive facility millions of times per second until the two beams

of particles converge at one of four collision points. They're the particles collide with such force that they annihilate each other, and we look at the reaction to learn more about the fundamental nature of the universe. That's the short version. Now let's dive into a longer one. Now, first, what the heck is a hadron? Well, technically, it's a particle that has made up of quirks, antiquarks, and gluons. Oh,

our definition has raised the need for more definitions. Alright, So a quirk is the sound made by a dirk. I'm just kidding. I stole that joke from a book called Science Made Stupid, which as a kid I thought was the pinnacle of humor. A quirk is actually a family of elementary particles that come in different pairs, So you could have an up quirk and a down cork. These paired quarks have a similar mass but different charges.

Quirks are bound by the strong nuclear force, which is the strongest of the four fundamental forces in the universe, and the other three are the weak nuclear force, the electro magnetic force, and gravity. While the strong nuclear force is the strongest of the four fundamental forces, it also operates across the smallest distances, so it's a very strong force, but only at distances that are on the subatomic scale. An antiquark is the antiparticle component of a cork. Everything

turns into another. Call for a definition, So an antiparticle is one that is identical to a subatomic particle in mass, but opposite to it in electric and magnetic properties. When these two otherwise idea nicle subatomic particles encounter one another, a particle and its antiparticle, they annihilate each other. If you've heard about matter and antimatter, it's that concept. When our universe formed, for some reason, there was a teen c tiny bit more matter than there was anti matter.

If the two had been equal, they would have annihilated each other and we wouldn't have you know, movie theaters and caso and stars and stuff. So an antiquark is the antiparticle two quarks. But what are gluons. Well, these are neutral, massless particles that are forced carrying particles. Sometimes they are called messenger particles of the strong nuclear force, and there are eight different types of gluons, so you're gluons. Quarks and antiquarks are bound together to create certain subatomic

particles like protons and neutrons. There are lots of them in every sub atomic particle, like a countless number of them, and number is constantly changing. Within a proton, for example, there's a shorthand and somewhat misleading statement that protons are made up of two up quarks and one down quirk. But that sounds like there's just three quarks and a proton. Nothing can be further from the truth. There are zillions

of quarks inside a proton. The shorthand actually means there are two more up quarks, then there are up anti quarks and one more down quirk than down anti quarks. So it's sort of a microcosm of a well, I guess the macro cosm of the cosmos itself. Remember when I said there were you know, if there were equal amounts matter and anti matter, everything would be annihilated. Well, there you go. Theoretical physicist Matt Strassler has a great article about this that makes it easier to understand and

in that article. He explains that a proton consists of these uncountable elementary particles with gluon's moving around at near the speed of light, sometimes appearing or disappearing. And he says, your hydrogen atom, which consists of a relatively stationary proton as the nucleus and a single electron zipping around it speeds far below the speed of light, is a peaceful example of balance compared to what's going on inside of a proton. And then he uses this analogy which I

love so much I have to quote it directly. He says, in short, atoms are too protons as a pod to do in a delicate ballet is to a dance floor crowded with drunk twenty something's bouncing and flailing to a dj That that image really works for me. Particle accelerators like the LHC smash open subatomic particles like protons to study these elementary particles and their behaviors, as well as to suss out the fundamental secrets of the universe. So I started off this whole rabbit hole by asking the

question what is a hadron? Well, hadrons include not only protons, but also neutron, pion plus articles, kon plus articles, and other stuff that's more exotic than your basic atomic science class typically covers. The commonality between all of these particles is that they are made up of some combination of quarks, antiquarks, and gluons, and the nature of that combination determines what sort of particles they are and thus their physical properties.

The Large Hadron Collider's mission is to smash these sorts of particles apart, violently and at great speeds. All right, so let's look at some history of how the LHC came to be, and then we'll look at how it do what it do. In n four, the European Committee for Future Accelerators met with CERN to discuss a new particle accelerator facility. And CERTAIN is an amazing organization. You may recall that Tim berners Lee, who is credited as being the father of the Worldwide Web, he created that

first web page for CERN. He was working for CERN. So CERTAIN has had a very important role in technology for years, and it's gone well outside of just the realm of particle physics. And I can't believe I used the sentence just the realm of particle physics. So this new facility they started to talk about was an idea for a new collider. The event's name itself was the Large Hadron Collider in the l EP Tunnel. That was what they called it, the Large Hadron Collider in the

l EP Tunnel. L EP is an acronym for the Large Electron Positron Collider. I'm sure you know. An electron is the negatively charged subatomic particle that typically orbits an atomic nucleus. It's also the basis for electricity, but you've heard me talk about that enough recently, I'm sure. A positron is a subatomic particle that has the same mass as an electron, but has a positive charge, not a

negative one. The magnitude of that charge is numerically the same as an electrons negative charge, except we're talking positive instead of negative with positrons. It is therefore the antiparticle to an electron. Unlike protons, which are a type of hadron, electrons and positrons are fundamental particles that cannot be split into any smaller particles. They interact through the weak nuclear force, not the strong nuclear force. This puts them in a

category of subatomic particles called leptons. This also includes stuff like muons, electron neutrinos, and various antiparticles. The Large Electron Positron Collider became the largest electron positron accelerator ever built. Planning for the twenty seven kilometer circumference tunnel began back in nineteen eighty three and construction ended in nineteen Digging the tunnel took three years, using three tunnel boring machines. You know, we talked about those in that Elon Musk

episode about the hyperloop and the boring company. Those tunnel digging devices are pretty slow. A snail is faster. The l EP itself was commissioned in July nine, with the first beams circulating on Bastille Day of that year. That's July fourteenth, in case you aren't up on your French history. The first collisions allowed scientists to produce and observe z bosons. So now we have another question. One the sam hill

is a boson? Well, at first I thought a boson was the sailor who was in charge of equipment and crew aboard a ship. But as it turns out, that's a bow sun, which is actually spelled like boat swain, and that has nothing to do with particle physics, unless you're talking about very tiny boats, Noah. Boson is another type of sub atomic particle that has a spin that has a quantum number of either zero or an integral number. Does that clear it up all right? Well, this might

be more helpful. According to Einstein's work, all particles in existence fall into two broad categories. They are either fermions or they are boson. This is all based off of math. By the way, Einstein's math only really works if this supposition holds true, and so far it seems to be so. Bosons include particles that can all do the same thing at the same time. For example, a photon is a

type of boson. You can make photons line up in a specific direction in a specific phase, and you can create a laser beam with a precise wavelength of color. All the photons within that laser beam are behaving in the exact same way. Fermions cannot do the same thing in the same place. Electrons are a type of fermion. They cannot orbit an atom in exactly the same way. You can't have two electrons orbiting the atom exactly the same way. Fermions include charged leptons such as the electrons

and positrons I just talked about. Bosons include the force carrying particles as well as the Higgs particle. More about the Higgs boson in a little bit. Okay, so the Z bosons and the W bosons are responsible for the weak nuclear force. Later, the l e P was souped up so that they could produce pairs of W bosons. For eleven years, scientists use the l e P to learn more about these mysterious particles, producing them in the millions. On November two, two thousand, the l EP shut down

for the last time, to be dismantled. In its place would be the Large Hadron Collider. While the l EP project was still in action, other groups were forming to create the teams and facilities that would be attached to the l h C. One of those was Atlas A t l A S. Atlas is a detector that captures information from proton proton collisions. It would become one of four collision detectors along the path of the LHC. It and the CMS detector are the biggest of the experiments

running on the Large Hadron Collider. There's also alice A, l I C E and l h C B detectors that look at more specific phenomena. They sit in big caverns along the LHC ring underground, but in this timeline we're talking about, they were still just ideas. At that point, the LHC itself had not yet been approved and the l e P was still in operation. The CERN Council

would approve the LHC project in December nine. In October, the project leaders published the LHC Conceptual Design Report, which included the idea of these four detectors and their arrangement around the perimeter of the LHC ring. CMS and ATLAS would both get official approval in January. The following month, ALICE would get the nod That happened on Valentine's Day, Happy Valentine's Day. Alice. LHC B would be approved on September.

There are other experiments connected to the LHC with scientific instruments that are near the big detectors and that look at specific phenomena, but the four detectors are what most people are familiar with if they know anything about the LHC. That is two years after the LP shut down, so this would be two thousand two. The ATLAS cavern was completed. Atlas is the largest in volume of all the detectors

I mentioned earlier. We had a team of producers meet with scientists who work with the large hadron colliders, specifically with the Atlas project. One of those scientists is Stephen Goldfarb. Here's how he explained Atlas's role in the LHC SO. Atlas is is one of four large detectors that sits at the collision points on large hadron collider. Large hadron collider brings protons around and accelerates them and has them collide at four different places. You surround those places with detectors.

Atlas is the largest in volume of these detectors. It's about a half of a football field in length to give you an idea of the size, and packed full of sophisticated equipment. It's one of the most complex devide is I think ever constructed. About a hundred more than a hundred million different channels of information come out of this thing. Its rule is if if you like an analogy. Is perhaps the strongest lens on a microscope that's ever

been built. It's to look into nature and to try to understand what we're made out of what are the fundamental components of of of matter and then to understand the rules around that. And we're making some big steps forward, but we still have some major questions to try to answer. Now we've got a lot more to say about the LHC, but before we dive into the rest of it, let's take a quick break to thank our sponsor. We're back now. These detectors have to capture information coming from a sub

atomic scale. Those collisions often will create situations that will blip out of existence in just just a moment a fraction of a second, so the measurements have to be not only precise, but also happen faster than I can even imagine. That also means that every observation generates an enormous amount of data. So the challenges with the LHC aren't just with the physics of getting streams of sub atomic particles accelerated to near the speed of light and

then making them smash together. It's also a lot of sorting and analyzing data to find meaningful information hidden in those collisions. So it's a monumental amount of work. Back to the timeline, the CMS team finished the cavern for their detector in two thousand five. Two years later, the last of the LHC's super conducting magnets were locked into place. Those would be dipole magnets, and this particular one was

dipole magnet number one thousand, two hundred thirty two. After each magnet made the journey down that through the shaft to the level of the tunnel one feet below the surface, they were loaded into a special vehicle that would take them to their destination at a blistering three kilometers per hour. You had to go super slow so that you don't end up damaging these delicate and enormous pieces of machinery. These magnets are are huge. The LHC wasn't ready to

begin warming up until two thousand eight. At ten a m September two thousand eight, the LHC fired a beam of protons around the ring for the first time. Unfortunately, on September nine, two thousand eight, a fault in the electrical bus connection between a dipole and a quadruple caused some mechanical damage and released some liquid helium from the system. This set work on the LHC back by about a year.

On April thirty, two thousand nine, the final replacement magnet, the fifty third replacement magnet, was lowered down to complete the repair work from the September two thousand eight accident. November two thousand nine saw particle beams again traveling down the LHC path. The LHC conducted collision experiments through November and into December two thousand nine. It then shut down for the winter, which the LHC does every year in

order to conserve some energy. And during those first collision experiments, scientists were working with collisions on the scale of two point three six t e V. T e V stands for terra electron volts. An electron volt is a unit of energy equal to one point six time ten to the power of negative nineteen jewels. It's equal to the charge of a single electron moving across an electric potential difference of one vault, which you know that sounds like a lot, and on a sub atomic scale it is.

But to give you an idea of what kind of energy we're talking about, a mosquito flapping its wings is the kinetic energy equivalent of about one terra electron voult, so two point three six tera electron volts on the macro scale is incredibly tiny. November two thousand nine also saw one of the stories that got a lot of circulation in the early days of the LHC, which was

the system shut down due to a bread eating bird. Now, the way the story was reported was that the power supply to the LHC got frazzled, and when engineers went to check where these connections might have shorted out to see what the problem was, they found a bird eating bread over a power circuit. Crumbs supposedly caused the problem. According to CERN, however, this wasn't necessarily the problem. It might have contributed to the issue, but they don't really know.

The truth of the matter was that the power site, uh, there were some feathers, there was some bread, and that was about all they could really say for sure. Power was restored and the LHC experienced only a minor delay. In February, the LHC began to circulate beams in preparation for more collision experiments in the spring, culminating in two three point five terra electron volt proton beams circulating by March.

This eventually allowed ATLAS to capture information from seven terra electron volt center of mass energy collisions for the first time. Skip ahead to December, when researchers at the LHC had begun to tune into data that could potentially prove the existence of the at that time purely hypothetical Higgs Boson particle. The Higgs boson is a particle that explains why mass exists, as in, why does matter have mass? To dive into more detail about this would require someone far better versed

in quantum mechanics than i am. In two thousand twelve, on July four, scientists that the CMS and ATLAS detectors confirmed the discovery of a particle consistent with the Higgs Boson hypothesis. Atlas scientist Kate Shaw talks about that experience so well. The classic story with Atlas is of course the discovery of the Higgs boson. So this is really one of our miles staying discoveries we've made. And this is a long story of over fifty years of fifty

years old. So it began with us trying to describe the universe. There was a big problem where we didn't understand why some particles had mass and other ones didn't. And so some theorists at the time, including Peter Hicks Um made a prediction of a way that these particles can have mass, and they said, if it's true, then there should be this thing called a h exsposon. Now at the time they said, don't even try to look for this because it's too difficult, it's too rare, you'll

never find it. Do not invest in, you know, accelerators to do this. But fifty years later, we have the technology and know how to make these fantastic particle accelerators, and we've been able to find the Higgs boson. We found it in two thousand and twelve. And that's a fantastic thing that these things were just were predicted fifty years ago, and only now are we actually able to find and prove these theorists correct. In February, the LHC ended its first run of experiments and shut down to

undergo adjustments for more powerful experiments in the future. The estimated downtime was that approximately two years. On June three, two thousand fifteen, the LHC came back online, conducting collisions at an energy level of thirteen terror electron volts, much greater than any particle accelerator ever before. Now I've talked about what's going on generally speaking with the LHC, but how does it work specifically. For one thing, all those

magnets have to be really efficient. To maximize efficiency, the LHC uses liquid helium to cool components to just a hair above absolute zero kelvin. Zero kelvin represents zero molecular movement. The molecular movement is essentially heat, so we're talking very very very cold here, colder than space. Even had that temperature, you can get super conductivity, in which a conductor is perfectly efficient and loses no energy as heat. There's no

resistance in a superconductor. This is why power allages are a really big problem for the LHC. The power goes out and the system begins to warm up as liquid helium stop stops circulating through the system. If it heats up enough, it loses its super conductivity, and you have to wait until you've cooled it back down to that

hair above absolute zero before you can begin again. They actually use liquid nitrogen to cool it down a certain amount, but liquid nitrogen isn't cold enough, so that's why they have to go to liquid helium. After it's been cooled down. To a certain threshold. So here's how getting those collisions to happen works. First, you start with some hydrogen atoms. The standard hydrogen atom consists of a single proton and a single electron that's orbiting that proton nucleus. Then you

strip the electron away from the hydrogen atom. That leaves you with protons, those positively charged sub atomic particles. The protons enter the line act two L I N A C two. This is a machine that organizes protons into beams and fires them into an accelerator called the PS booster. The PS booster uses radio frequency cavities to accelerate the protons, so it's an electric field that pushes the protons to

increasingly higher speeds. Because you've got a charged particle, you can use the opposite charge to pull the particle toward it, or a similar charge to push the particle away. So you just use that to increase the speed of that particle as it travels around this particular part of the accelerator. Magnets are there to make sure the protons stay on the right path. The magnetic fields kind of act as bumper rails for the protons. When these beams hit the

correct energy level as determined by the experiment. They pass from the PS booster into another accelerator called the super Proton syncotron, which I was pretty sure was a Decepticon robot in one of those Michael Bay movies. The beams continue to accelerate and the protons separate into bunches. So think of groups of protons traveling a circular path, picking up speed constantly with other packs of protons right in front and right behind them, and each bunch is pretty big.

I'm talking one point one times ten to the eleventh power of protons with two thousand, eight hundred eight bunches per beam. Once this beam hits the next threshold and energy levels, the SPS then injects it into the actual l h C. The beams divide into two. One beam travels around the kilometer circumference clockwise and the other one goes witter shans, which, as you all know, is my

favorite synonym for counter clockwise. Now I'll talk more about how this works and what comes out of it in just a second, but first let's take another quick break to thank our sponsor. Alright, So those two beams, which have already been accelerated through a couple of different prior

accelerators before going into the LHC. They enter the LHC, they're going in opposite directions, and after about twenty more minutes of excel A rating, at which point the two beams are going just a fraction below the speed of light, powerful magnets aim the bunches to converge at collision points. Now, protons are very very tiny. They are sub atomic particles, and it is super challenging to make sure you get

two to collide with each other. That's why you have bunches with so many protons per bunch to help make sure the collisions actually happen. As an analogy, imagine that you are inside a an indoor stadium and you have a super bouncy ball, and you are at one end

of a football field. You have a buddy with a super bouncy ball who is standing at the other end of the football field, and both you and your buddy are blindfolded, and you're both told to throw your super bouncy balls where you think the other person is with the aim of having those two balls collide in mid air. Will those bouncy balls collide? Probably not, And even this analogy doesn't give you a sense of scale of what

we're talking about. When we're chatting about protons, this would be this would be incredibly tightly controlled in the proton world if we were to take it at scale. So it's really hard to make sure you get these sub atomic particles to collide with one another. The precision of the system, coupled with the number of protons helps make sure that there are enough collisions to make the experiment worthwhile, and we're talking on the level of six hundred million

collisions per second. Upon colliding protons behave in very interesting ways, sometimes in ways that are hard to get your mind around. Kate Shaw explains, I think there's many concepts and particle physics that I find very difficult to explain. Um. I think one of the things that I think is always vital to communicate and always is difficult is the fact that when we are doing partial collisions in the Large Headland Collider, we're not just colliding protons together and they

crash and you see what's inside of them. It's you know, if you imagine throwing together to bowling bulls high energy, you can imagine they break apart and you can see what's inside of them. But with the large hat on collider, we're colliding things together and the particles annihilate one another. So these particles that are made of mass annihilate one another, turn into energy, and then turn into different type of mass um and then we study that. So it's like

cliding apples together and getting bananas out. So this is always a complicated thing to an expect to explain, and a really kind of intrinsic part of what we do. There are some things the LHC might uncover but hasn't yet, such as evidence of extra dimensions or some observable proof of dark matter. In the process of searching for these things, scientists may create some stuff that makes some people unjustifiably nervous,

like a micro black hole. And while the LHC could create a micro black hole as a result of a high powered collision, it's not the same sort of cosmic boogeyman that serves as a major device in various science fiction films. Stephen Goldfarb explains, now that got a lot

of people very excited they're going to produce a black hole. Well, a micael black hole is something which has the energy of a mosquito, and it will always have the energy of a mosquito, and so it's something which will be produced and it will disappear instantly, and we can measure that.

So one way that helps to get this concept home to everyone that what we're doing is at very low energy, yet it's something that's It's interesting is that Mother Nature, uh from charge particles produced by the Sun colliding with her upper atmosphere, has already done the l h C all of the collisions that we'll do in the l a C about ten thousand times before, and things are

pretty much okay here on Earth. In July two thou seventeen, researchers at the LHC announced that experiments had uncovered a new part call and it consists of two charm quirks and one up cork. Keeping in mind the same rules we mentioned before that in fact, there are zillions of quirks there, but we're talking about the number of quarks that exceed the number of their respective antiparticles. What makes this particular new particle interesting is that it has two

so called heavy quarks, those being the charm corks. Other particles of the barry On family have at most one heavy quirk, and there's talk of this new particle giving us a deeper understanding into the nature of the strong nuclear force. The new particle's name is sigh c C plus plus, but I think we should just call it Larry. Before I sign off, I want to talk about some fun, goofy stuff about the LHC, or really about people thinking

about the LHC. The black hole story made some people flip out, hypothesizing that the collisions that the LHC could potentially destroy the world and create a black hole that would in our solar system into a waste land. There's even a cute little gift that shows the area outside of the large Hadron collider suddenly collapsing in on itself.

But as Stephen Goldfar mentioned, that's not realistic. Collisions on the order of what happened at the LHC happened all the time in nature, so there's no reason to fear them here on Earth. If they really were that catastrophic, we never would have made it this far. Earth would have been destroyed long before any advanced life could have evolved. So that's a relief. But then there's the other story. This is the one I love because it's so goofy.

This was a hypothesis which may or may not have simply just been a joke that the LHC itself was manipulating time so that it could not be turned on to cause massive amounts of harm. You know, we had that early problem with the LHC in which liquid helium was spreading throughout the system and they had to shut it all down, And then there was the bread being dropped by a bird. The hypothesis said that all of

this was evidence of temporal tampering. Has some sort of entity from the future, perhaps an agent formed by the LHC itself was sent back in time to prevent the LHC from ever firing. So I'd like to think that a future saboteur would be a little more practical than this whole bird bred story. The LHC has been operating for years now, so clearly, if the temporal hooligans were involved at all, they've knocked it off by now, which is good. There's science to be done and making a

note here huge success. As for why some LHC folks were at mog Fest, will not only is mog Fest concerned about technology and science. In addition, to music, but you can actually find quite a few bands that have formed at the LHC. There are a lot of musicians who are also scientists or engineers or data analysts, and

they have often played together in various groups. So I reckon, then you check out the LHC music scene, because you might not just learn something, you might also get the boogie down that wraps it up for this update on the large Hadron Collider. I would love to hear from you guys about any topics you would like me to

cover in future episodes of tech Stuff. You can always get in touch with me by sending me an email the addresses text Stuff at how stuff works dot com, or you can drop me a line on Facebook or

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random stuff. So if you want to be part of the conversation, go to twitch dot tv e slash tech Stuff, check out the schedule. You'll see when I'm streaming live and I will talk to you guys again. Really simple. For more on this and thousands of other topics, because it how stuff works. Dot com