Osher Particle Physics Lecture 3 Transcript

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Let’s kind of warm up slowly, let them some peoplele in. Okay, so yeah, so this is the this is kind of the big day and the uh.ure series. This is what we've been building to for a while. 
And so um I should I can't just say, this is super, super advanced stuff. So if some of it is not clear, it's you know fine. And the other thing I'm going to try to do is I'm not going to cut any quarters. 
I'm going to tell you exactly what the mathematics is saying without making analogies means though it's be a little bit complicated, this will probably well, I think thechanics is the most difficult part, but this is also very complicated, so there's lowering the bar, you know what're, but I can't explain any of it. these gift certificates. Okay, so just a reminder of the big picture, so we we had this idea of these scientific explanations seem to be converging. indication that we're perhaps making progress that stops in the 20th century where it looks like we hit a wall, right? And there's two scientific revolutions that get us past that wall. 
And we talked about those space time coming from relativity and the idea of quantum mechanics, from the whole field. And again, these are these are revolutions in the sense that it really changed what physics was about, right? So the whole part of the game was questioning things and coming up with new ideas. 
So maybe maybe the physics that we have isn't right and we need some new new wayated proceed. so it's kind of revolution revolutionary in that way. Once those two pieces were in place, then progress was very, very rapid. So in the 20th century we made tremendous progress, both kind of philosophically, we can now explain why matter is stable, like chemistry works the way it does, and so on. and we can also make, you know, tons of technological progress, right? 
So we get the transistor, we get the modern economy mainly coming from from quant can, is more important there. Okay, so rapid progress technologically and in terms of scientific explanations, until you you need to combine systems in like in particle physics that where space time is important, so the particles are moving close to the speed limit, the ideas of space time are relevant and the particles are small this thick the thickness of the line becomes relevant. So that's the first in particle phys need to put both of these two ideas And what happens is it looks like it doesn't work, in it doesn't general it doesn't work. 
So you try to do and it says, well, you need antim, if you don't have antim people at the time think there was antimatter, then you get caus violated, get causes coming get effects coming before causes. If you try you try to describe a spin seven particle, it's fine in quantum mechanics. If you try to put in it with relativity, it looks like things go faster than a speed of light. 
So again product. If you if you want to have a spin one particle, which is totally allowed in quantum mechanics, that you think there's a firm on, so it behaves like a classically like a matter matter particle. That again is totally fine in quantum mechanics. 
It does not work if you try to put itatively,? So the most things you can do looks like it' the physic no big deal. They were just trained, the people that were actually trying to solve this problem were trained, you know their bosses were the ones responsible for revolutions in the early 20th century. 
So they thought, no problem. I know what to do. more revolution. We need to come up with new ideas, you know, new things, we need to throw away chron mechanicsivity come up with new things. 
So if you look at the history of this time, it's really, really confusing because you have people trying these you know, they're trying to change things, trying to do ideas. None of them works. Okay? 
So we now know the answer is to actually be very conservative, okay? So instead of coming up with new ideas, you instead insist that quant mechanics and relativity are the ideas and let's try to do whatever we can to make to make them compatible, okay? So with the first revolutions, it was about changing changing the laws of physics. 
Now it's about changing how the world can possibly be to fit these ideas. So it's saying, okay, if if you combine complicates of relativity, if it implies, the world has to have an matter, that means the world has to have an. If you can only describe particles that have spin two or less, that means you're only allowed to have particles of spin or less And so basically putting restrictions on the world. think about cont activity, but there are these kind of isolated spots that where if you restrict the possibilities, you can get it to work, okay? 
But just fair, it's very restrictive. Right? And so in that sense, it's conservative. 
It's conservative in the sense that you're not coming up with new ideas, you're forcing the ideas that we had from our forefather. Okay, and that really restricts the way that the world can look. have a question like theory revolution's nothing to do with that nothing to do with string theory. And at the end of the last lecture I'll a little bit about string theory. 
Okay, and so you know, on one hand so actually this is really nice to be conservative because you don't have to come up with new ideas, you can just insist on the ideas that you already have, and most of the things are ruled out. So you right? So if they're compatible, it's making pred the way the world has to be, so it saying there has to be anti. 
It's saying you can only have particles that spin zero, one. It's saying there's this correspondence that the and so on. and behold that the the world looks. when we go look and do particle physics, we see an particles that have different spins, but none of them are the spin too, and they all have these correspondence of sp spin p now it looks great because you put them together, you had to be conservative to predictions. Those predictions were all correct, to be correct now we're hit another, okay? 
And so's where the airport so the case comes in. Okay, and and so again, we talked about this this last time we have what's called a standard model, so this is a version of relivistic quantum mechanics, so with the quantum mechanics in space time, basically. And we think this is the one that describes our actual universe, okay? 
And we we it has these particles again they fit they fit the patterns that we expect, so we have these particles that we finger fundamental. They're all spin and half particles, so that's one of the allowed options. and they have the quant mechanics and activity says they have to be spin half or they have to be fermions and they see that they are fermions. it also tells us about the forces of nature of how that particles interact, and those there's a particle has to be associated with each force. Those particles have been seen. 
There's spin one, and that skin of one of the allow options, and they have to behave likeically like light as wav, so they have to be boszons and that's consistent as well. Yeah, so spin is something that we don't really understand either. it's like the way to even think of it, so in the equations, it's kind of like it's kind of like the Earth, right? So the Earth has angular momentum around the sun because it's orbiting the sun, and it's also spinning on its axis. 
And so that spin can interact with it acts like a form of anome. Now, uh so it's it's very much like these little articles are spinning, except the point-like particles. So they're not exactly. 
It's not like there's something in space that's spinning. It's just but but that's a convenient way to think about it. The equations work that way, but it's really just like a fundamental label that the particle can have that looks a lot like spin. 
I think it's a mystery wide. It really a deep level wide they spin. it looks under spin. Maybe it's a hint that' for instance. 
Okay. um good. And so we said at the last time that this is this is great, because it's it gives a qualificated prediction uh for what we see, some of this would give was forced on us by the experiment, right? So we weren't expecting these other families or these other generations, copies of the particles that we know in the periodic cable, but the theory can accommodate them. 
And once you discovered that we can now we can test these make predictions and those predictions qualitatively and in many cases very quantitatively agree with the theory. so hand it looks like theory is great making these very precise predictions. On the other hand, the theory is actually only consisted if all the particles areasimless, okay? And this seems to be a disasteraster, okay? 
And this is where they so, you get a wall, right? So it looks like it works, everything's fine. Now the theory is making you know it's predicting probabilities that are infinite, and so a lot of people said, okay, we just need new things, right? 
We need we need to go beyond quantity. Okay, but there's okay, so this is a serious problem. and this is the importance to the head. So today's is about theiggs and really what it was it's something that's grafted on, right? 
So we have this really nice that we like, except makes some predictions that are crazy. predicts infinite probabilities and it's theoretical community theoretical physic did they added to the that you hear in the media about thes like this, so some people say the Higgs goes on or god particle is responsible for all mass in the universe. Okay? So this is something that we impressed. 
So after at the end, we'll come back to the statement and see if it's what it's true. Okay, so so the question is, what's the problem withAS? Okay, so why does it know why is the pro the problematic that these particles have masks? 
This whole goes back to this idea of spin again, that we don't really understand it at a deep level. Okay, so remember, spin is something that's really forced on us by quantum mechanics. plus relativity, you have to talk about it and there's these connectionsctions between photons and fermions and so on. Okay, but let's just focus on the matter particles. 
Okay, so matter particles have the spit half and what regular quantum mechanics set, that means there's only two ways that the particles can spin. So again, think of like, it can either it need to be spinning clockwise or it be spinning counter clockwise.? And it's a little more complicated that you have to pick a directionant says you could pick any direction and then along that direction, it's either spinning the clockwise or counterogwise. 
Okay, so a good direction to pick is the direction that the particle is moving. Okay, so let's say we have a particle moving in space on this ais, then, you know, a long to the right, then it could be spitting according to your right hand, right or say according to the left hand it could be spitting again, it's not really spitting, but it's as if it's spitting like this, which we call it a right hand or spitting the other direction as if it's left-handed.? So two different different particles can'. 
Okay, so that's one thing. field theory, so when you put in relativity, it says that if you have massive particles, then what happens is even if they're in empty space, they can flip back and forth between these two. Okay, so it says that if you have a particle it's moving it get no interaction. It's just propagating in empty space. if it starts out at the right as right hand, it'll flip to be left hand. 
And it'll flip back to being right hand and it'll do this kind of flip flop. And the rate how quickly it flips back and forth is related to its mass. So if it has a big mask, it'll flip back and forth more if it has a small mass, it won't flip back and forth as much. 
Again, this is a result of putting together relatives. heavier it is the flows back forth. Okay, so instead of drawing these circles, I' put red and blue lines. And so this is like spin along the direction of motion, this has spin the other way. 
This should be not time. This is like as it mov. Okay, so so what's the problem? 
So so now the other thing is the part of those can do is they can interact. Okay, so an electron that's just been in a half particle, it has it has a charge and and we say, because it has a charge, you know, there's some non-zero value for its charge, it can have this interaction with the electr magnetic force carrier and the charge is related to that probability for this to happen. Okay. 
So that's that's for the electragnetnetic interaction. There's a similar thing for the weak force, okay? The electrons also have something that's called a weak charge or we say hypercharge. 
Okay, so again, it's just a word to just like charge is some word that is the strength of the interaction with theonpercharge is a word that characteriz the strength of the electron interaction. electr electrom hyper.. That was crazy imagine what is the hypercharge depends on this thing, depends on the direction you spin. Again, this is probably a sign that spin is not there's something deeper at the spin than just the direction of the spinning. 
But what we see is if they're left handed, they have a hypercharge and they feel the weak force they're right handed they don't it's as if they don't feel a weak force. there for electrons. for the election.. the same behaves so differently in the right hand it's have an electron electron in this direction, why do we call them both electrons?, this electron, they're identical identical. There's sym right aer that if you that's faster than that particle, it's look like the spin flips. Right, if you could think of it, it's hard if you were if it spin in this direction, so the spin is going this way, if you're at rest with the electron, it looks like it's right handed. 
But now, if you're moving faster than the electron, the spin stays this way and it looks like the electron is going that way, so it looks like it's left handed. So the deep reason we think left handed and right handed particles are related is because there's a symmetry a different the same right hand. can youel one as aer. The whole will be observer. 
It's like it's winding and unwinding kind of like that it seems like. Yeah, it's. Okay, so what's the problem here? 
The problem is only left-handed particles of hypercharge. So the problem is now, for one observer, the particle is gonna be flipping back and forth because it has an asked. But if you think about the hypercharge, it's then one and then one, so the hypercharge does not look like it's conserved or it's not conserved. 
It's from zero to one. And one of theto, on one hand, quanelter of putting these two things together tells us that massive particles must flip back and forth. in our world these have different hypercharges. so this implies that hypercharge cannot be conserved. So on one hand, it seems to be saying that hypercharge can't be conserved, but on the other hand, remember what it thinks last lecture is that all a charge it must be const. 
This was a basic consequence. So again, it looks like we're an impse, right? Damn it, but hyper is different and right particles, it looks like it's an inconsency. 
It has to be obser and it can't this? it's an interaction, it would be plus one timesha, basically. and here, it would be given by either plus one times a week alpha or zero times a week. exactly.. Okay, and so the way to get around this is using a field that hits field. 
So actually, it's the hits field is important, not the hitos. Okay, so what the hell is it feel? So a field is something that you kind of already know about. 
It's a fancy word for for just saying weap a number or maybe a set of numbers each point in space, okay? So like a temperature field would be at every point in the United States, what is the temperature? Right? 
Or you could have so that that would be one number at each point in space. Okay, if you think about the windfield, that would be like three little numbers or an arrow at each point in space. Okay, so the field is just a fant saying it's a mapping of a number or set of numbers each point in space. 
Okay, that's a field. So so how does this this okay, that's what our said. So how does this help? 
Well, the first thing to point out is most fields cost energy for being on. Okay, so for instance, let's say there's the windfield in this room, okay? If the windfield is zero, there's no wind blowing. 
Okay, if I want to determine the big if I wanted to turn the wind fuel on to have some big value going in this direction, I have to put on you know turn on some fans to blow the wind, that would cost energy. It would cost energy to turn on these fans. So usually if you look at the this is now the field value so that the zero the field being off is the lowest energy point. 
If you want to turn the wind on to the left, that's going cost energy. If you want to turn it onto the other direction, that will cost energy. Same with electric fields. 
If you want a big electric field in the room, you could connect you, put up big piece of metal connected to a battery and and that battery is gonna cost energy to turn on the field on rock. Okay, so this is how this is how all the fields, basically that we know look. Okay, they have the minimum zero and it costs energy to turn them on. 
Okay, so we're gonna use this idea, but I'm gonna warm up with an example of how a field can affect the mass. Again, this is this is kind of a cartoon example, but it's it's one that's exactly analogous to the case of the Hicks Hicksburg Hicksfield. Okay, so let's start with water molecules. 
Okay, so water molecules are neutral, but you might know they actually have this charge of balance, so so the the oxygen and it tends to be on one side and the hydrogen on the other, so they act like little thive poles. Okay? And this is why the water is actually so good at cleaning things just because there's kind of an imbalance of the charge that can break break other bonds up. 
Okay, so you can think of it as as like a little thighole, right, with you know more positive charge on one side, more negative on the other. Okay, and so now let's begin thinking of spin, let's imagine we can only have up electrons and down electrons. Okay, so let's let's say I have some experiment where I can force the electrons to you to be pointed up or pointed down. 
Okay, so we'll say we have up water and down water. Okay, now, of course, space is symmetric, right? It doesn't matter which way you look, so the mass of these is gonna be the same. 
The mass of theput doesn't matter which way that they're they're forcing. They're they're facing. So now let's break this again, because the face is symmetric packs the case. 
So now let's break the symmetry and we could do that by again turning on a big electric field. So you could turn on electric field by connecting a battery to two big plates. This creates a constant electric field between the plates. and and now what happens is these electric these nipoles want to a line with the electric fuel, or actually they want to anty a line. 
I always forget. But now they're different, right? One of them has more energy than the other. 
Okay, so so if if you would just turn this on and let go, you would slip them all to be all lined up. But again, let's say we have some way to keep either up, up or down electrons. Okay, so we're gonna the up ones that want to flip, we're gonna hold it we're gonna say that there's a way that they're held in place, the downloads will be down. 
Okay, so now in this case, they actually have slightly different energies, right? There's higher potential energy for the up ones than for the downloads. And because E equals MC squared, that energy, that's the energy that they're just sitting there, right? 
It's just sitting there, because it's interacting with its electric fuel, it has a higher potential energy, and that potential energy looks like a mass energy. because it's an energy of just sitting there, just sitting in this, it's not an empty space anymore, right? It's just sitting there in this electric field. it's in the wrong spin orientation, it's if it wants to flip the other way, it will have higher potential energy from relativity looks like mass because ev is M squared. Okay, this is a tiny, tiny mass difference, we could put these electric the biggest electric fuels we could make would be a tiny, tiny correction, probably couldn't even measure it. but if you would do an experiment, if you would try to accelerate these water molecules and compute equals MA, you know, if you know the force that you're applying, measure the acceleration, if you could do it precisely enough, you would detect different masses. in the spin of the spin down. 
Okay, so the key that's happening is we have some kind of potential energy of the particle just sitting there that gets interpreted as a mass. Okay, so that's that's the big idea here. The potential energy from just being just being there and equals entity squared that most like a mass. 
Okay, so what we're going to do when we come to the Higgs is we're gonna say, well, look, the particles are actually all massless. They have no mass, but they have this potential energy from a pigs spel, OK, and we'll talk about that in a second and that potential energy we can looks like a mass. Okay, so it's a trick. 
So it's a way to get apparent mass from potential energy where the particles themselves actually don't have maths. Okay, but we're getting ahead of ourselves. Okay, so again, this is an example of how a field can create mass. 
So if you can turn a fuel arm and you have particles that interact with that field, they would have potential energy and that potential energy could be treated as an mass. Okay? And again, this is sometimes you see the hatefield as like some moacular like this molasses and you it's something moving through molasses. 
That's really not a good analogy because the nalysis is put putting a force on that part here, it's just a potential energy. There's no you know, there's no thwwarfs at all either of these particles had look, but it looks like a mass. so that just. Okay, so yeah a question. 
It is theory is it's basically this is wait we get there. Okay, so now, of course, we're all sophisticated now they' electric field, come on, that's a classical thing. This is quantum mechanics, right? 
So what's really happening with electric fields? Well, if you return an electric field on, mechanically what's happening is you just have a C or a bath of photons, which are the force carriers for the electronagnetic interaction, that are constantly being emitted from these plates and reaborbed, and that's what effective or classically it's looking at long distances it looks like the electric field, but it's really there's just a seed of photons that are coming back and forth. Okay, yeah, so that's what I'm saying. 
So from the point of view of the water mole, if we kind of think of like a particle physics, um the water molecule doesn't live in an empty space. It doesn't live in a vacuum. It lives in this world where there's just photons everywhere, right? 
It's like it lives in this bath of photons. Okay, um so in this and this kind of toy experiment, the empty space where the vacuum where there's no other particles but one particle is really filled with all these photons from the electric field. And the fancy way to say this is there's a condensating photons. 
There's just so like that's saturated there's photons everywhere.? And so what it looks like is you down moving along and it moves a little bit in quote,emty space in between these char plates and it runs into a photon.? Because it can interact with the photon and then later because of it another phot another. from the point of view, there philotons everywhere and it's just a matter of it hits another one. 
So it's constantly hitting these protons and again at long distances that looks like an electric field. Okay, right. And so in this example, this photon condensate is created by us, right? 
We connect the battery at turns on the electric fuel and you know, you need energy to create these photons and that comes from this external source in this example. Okay, so now on to the real example, and this is the h field. So the idea is, well, wouldn't it be great if we could have a huge if we could have some other condensate and maybe we could get mass the same way? 
And we could have mass being potential energy. Okay? And this is this is using a trick. 
So the big question is, how do you turn the fuel on, okay? And so say is, okay, here's how we're going to turn the fuel on. Most, most potential energies looked like just a problem. 
It was it was a minimum it was at zero and there were the cost energy to turn the fuel off. What the theorists gave in like 60s and 70s said is that's true for all the fields except this case. For the Hfield the potential energy looks like this. okay? 
Why does it look like that? Don't ask any questions. It looks like this, and there's two things to point out. 
One is it has to be symmetric. That's important for the consistency that here. OK, the other one was symmetric too. 
This one has to be symmetric bad things happen if it's not symmetric make it symmetric symmetric point is no good because it's not a minimum, right? The world wants to live in the minimum of the energy. So what you have is that minimum in the energy could be here or it could be here. 
And it kind of doesn't matter which one it is but it's not the symmetric point to the theory. Okay, so what we say is this is an example of symmetry breaking or spontaneously symmetry breaking, where the underlying theory is symmetric has a symmetry, but the solution, the ground state is not symmetric point. And so if the ground state is here, that's not symmetric about you., this is a trick They' putting it in by hand, and of course, they know the problems that they're trying to solve too. 
Okay, so they do this, but by the way, we see it right and they're assuming this, right? So remember, there's nobody's seen Hicksfield at all, okay? And they say, yeah, there is this field that you've never seen, and it has this potential that doesn't look like any of the other potential that we've seen. 
Okay, they got this idea from other physicists that are studying really exotic things, like superconductors or superconductivity, superfluids. These kind of crazy exotic materials. They actually have something like this, and there's a good reason why it has this shape and it's not natural, right? 
It's because they're fine doing things very close together. They're doing some very complicated experiments. You can you can you can engineer this kind of shape. 
And when you do, that's what you get super connectivity. Okay? So this is this was an idea that was stolen from them and they're just assuming that this is true for this field that we've never seen. 
It should sound it sounds like BS, right? Okay, so that's what I' saying here. But the nice thing is the good thing about it is if if let's say that let's say that they're true, if that if this is correct, then you would you could turn the field on for no reason or just because it has a shape. 
The shape of this potential leads to the field of having, you know, either this value or that value. And again, it doesn't matter what so much wish, just that the value is non-zero. Okay? 
So if if there was this field that we hadn't seen and it had this crazy potential, the vacuum or empty space would naturally not be empty. It would have a condency coming from this field being turned on. Okay, um and again, this form is an input to the theory. 
It's an axiom. Okay, we just say it has this property. Okay, again, the upshot is, or you know, classically, you would turn this fuel on in particle because if you would say it forms a condensate of particles and we call these particles the particles. 
Okay, just as in our previous example, what would happen is if you had some interaction to this field in empty space, you would be constantly hitting theseV particles and they're kind of freed in if they hit they're just basically everywhere. Okay, so how does this help? Okay? 
How how does this help solve our problem? Okay, so the critical point is you also assume that these f particles have hypercharge. You say that they have no electric charge, but you didn't impostulate you assume that they have hypercharged one. 
Okay, so now what happens is we have our particle electron that's that's is going through empty space, except it's not empty now. It has its condens and it looks like it's well is flipping back and forth, and the electron is losing charge, losing hypercharge or changing hypercharges clips. But what happens now is you say aha, these flips happen because that's where you hit the compensate. 
The electron is coming along It's left handed. It hits this condensate, just like the proton case and that'sment, that's what's causing these flips. Okay? 
And because it has hypercharge one, now you can serve hypercharge. It has hypercharge two. It's coming along. 
It interacts with a particle that has hypercharged one. So zero plus one is one before, and now you get hypercharged one. Now it's going along as hypercharge one. 
It hits one of these other, you know, now it admits one of these particles and it flips the hypercharge zero. Okay? So that that's the idea. 
That's the way it looks like it was going through empty space slipping, but because space isn't empty, you have these condates. You have these particles everywhere. If the B particles have hypercharged one, then it can the electron can change hypercharge, but bar all hypercharges can ser because it's interacting. the particle has a hypercharge one. now theory is now hyperchargeved because the electron isn't really just flipping on its own it's interacting with this cond the Yeah, exactly. 
There's some amount of energy and that's exactly the right energy that gives the particle of the mass. Right. So that yeah, so electron thisle, a much heavier particle would would flip back and forth much more often. 
And what we would say is its interaction with the hypercharge is much stronger. Or with this becompensate as much as much stronger. Okay, what do I say here? 
Yeah, so I already said down. Okay, so that's how it works from that apart. Remember, there they only have spin there's only two options so they can flip back and forth by interacting with the dehanting. 
Okay, but there's other particles have mass, including spin one particles. These are the W and Z particles. Okay, so for these, both, again, experimentally, we know that both the left and right hand particles have hypercharged zero. for these these particles. 
Okay, but they're but they're massive, okay? So because they're massive, again they need to foot back and forth. But now it's not so easy because here I have a hypercharged zero particle, right? 
It's now the Coson. It can interact with with a hypercharged one particle, but it can it can't just flip to to the left-hand version because the left-hand version has hypercharged zero. So there has to be some new particle that has the same mass as the zos on, but has hypercharge one. let's call this particle. 
And so now we're assuming we're assuming that there's this other. We're assuming these other particles have the exact same mass has hypercharge. And now what can happen is this omega particle and interacts with condensate to turn back to the other the other. 
Okay, so it works out of the box for the matter particles for the for the it doesn't but it will if you add yet another thing, these omit these omega particle for the Z boson, then it works on. Okay, and it's the same thing for the W, except now you need two new particles because this W, there's two Ws, there's a positive W. There's a positively electric charge W and a negatively electric charge W. 
So if you want this thing to work out, you need little manas that are plus that have positive electric charge, negative electric charge, and the same mass as this W particle. Okay? So these are these are referred to as the longitudinal polarization of the W and the Z, and these have actually been discovered. 
Okay, so we've discovered these, so this is maybe a hint at this idea of working, but it still seems um it still seems super adoc, right we' making Okay, but the thing I wanna say that's amazing is most things that you do screws everything up, right? If you try if you if you try to say, okay, maybe I'll call up another idea that that can get mass the particles, maybe it can work, usually it just doesn't even work. But if that works, usually you screw up other predictions, you screw predictions of what happens when I collide these particles, you, what's the detailed calculation of this probability that has also been measured usually screw up those answers What's amazing about and another big hint that maybe it's not completely is that you can put this in and basically the only effect that has is allowing particles have a mass. 
You don't screw up any of the other precise predictions, it's not obvious that it's impossible to do that and the fact that it works maybe is another hand that it's correct. Okay but you see here it's Hicks field that's doing all the work. We haven't even said Higgs Boon, so so what's what's the deal with the Higgsoson? 
There's a couple ways to look at this. um Yeah, so there's the kind of there's a fancy way that I'll talk about in a second, but another way is if you have a Higgs field, that field can have sound waves in it and that those sound waves are what we would call the Higgs bos, okay? And so justicatively the Higgs bos are is interesting because it's a tracer for this idea. If it' idea is correct, you also have to have a new particle that's a Higgs bon, so it makes a prediction about there being a Higg boson. 
So I think that's the real reason why why the Hicks is relevant, because it tell you that this idea is correct. There's more technical reason why you have a Hoson which I talk about now. Okay, and so now we had to have these new particles, right? 
These omega particles. You can ask what happens if I okay, so we're not doing this experiment, but we're just asking, what happens if I do an experiment where I I have two of these and I collide them at very high energies, you can do the calculation and it says that this amplitude goes like the energy at which you collide them over the mass of the particles. Okay, and remember that if you square this thing you get a probability and this is dangerous because you can go to energies that are higher than, you know, there are 50 times higher than that of the W, and that looks like you're going to get probabilities bigger than one. 
Okay? And that's true. So if you if you, you know, you go to very high energies, and you square it, this becomes bigger than one. 
So this is, again, the theory is inconsistent it's sick in in the sense that it's telling you the wrong the wrong answer. Okay? There's some details if you put in if you do the precise calculation, you see that indeed this is what happens. 
You get probilities bigger than one at at some some energy. Okay, and so this is where the Higgs bon really comes in. Okay, so it turns out the if you had this field, there's gonna be sound waves or excitations of the hit that's the bon and what you say is well this has the this interaction. 
So this will interact just like the an interaction between these omega particles and thes. And again, this is a particle that's like a you can think of it like a sound wave in this V. Okay, if you if you include that, then there's two ways that this can happen. 
They can just directly interact or they can exchange one of these pigs boszons, and if you do it, it turns out this one is also divergent. It gives probilities that they are bigger than one, but there's a negative sign. just go away the mouth works out. There's a minus sign. 
So if you add them together, you get some finite result that's always below one., so again, another clue that maybe this is right. This thing is it actually gets infinite probability if you go to infinite energy. This one alone also gets infinite probability, but there's a because there's a relative minus side. again, details on how, you know, what couplings are assumed and you know how how big the interaction strings are. 
It just works out that there there was infinite infinite terms exactly cancel when you sum the altitudes., right it seems again, it seems like this isn't going to work, right? You do the most naive, stupid thing, it doesn't work. Then you have to remember, oh, yeah, there's this other sound wave now. 
I had that in and um and now you have a sensible theory again. Okay. Right. 
Okay, I'm sure there's a lot of questions about this.? It does, yes. It does. 
We'll come back at the end. We don't understand why. doesn't understand why it has massive.. So basically what have particles but you can do, you know calculations or say, I'm going to collide these things, you know, this particle collided, what's the answer? 
And it gives very good answers without the. you have to assume the particles have mask and yeah, you can ask other questions that give crazy answers, but you just don't ask those questions and you get the right answer. so on one hand we are in that situation, but theorists look at this and they're really worried about these other questions that give the wrong answer and they're trying to say, how can we fix that problem? And so they're just using pure math to do this? So they're just putting it in, they're just saying the not what's what thought was this other that has this crazy shape. 
Basically guessing, okay? And they did a bunch of these things and most of them didn't work, and this one seemed like it's working. you to go to the article collider and find the data. But if you're a feworeical physicists somewhere the world and you think about this stuff, maybe you make up your own teriture every day and and go, hey, what how does that get shared across the world of physical. the guy that this is named Higgs and he wrote about it and again, at the time there's a lot of people doing this. 
Most of them don't work. So you write papers that work and they fail in interesting ways, this theory so interesting almost, but it failed this way. And then because up with this idea't It wasn't just write a paper and you talk about conferences and he had to wait in order to see if it was actually right., there is yeah, I mean,000 in the most of them work on this problem, there was, I' experiment. 
That's. Okay, so now one question is we see how some masks can look like it's it can let's of the masks can come from the potential energy. If you turn the Hick on, if you're interacting with that or interacting with that common state, you have some potential energy, even being in the vacuum, which is not an empty space is filled with this common sink that potential energy looks likeounce energy by equals entity square. 
So one question is, does all the mass in the in our world come from the hazefield? OK? You often hear that it does, the answer to that is no, it does not. 
So here's an example. Let's say you have the kind of fictional example. Let's say you have a ball that had kind of met infinitely thin, reflective walls. 
Okay, so you have like a mirror and inside the ball, you have you have photons bouncing back and forth. So again, we're going to say that we can make this beer kind of arbitrarily thin, so it has almost no mats. And the photons don't interact with the Hicksel at all and they have no mats. okay? 
So you have this ball sitting there. If you do experience experiments on this ball, it will look like it has a mass. Okay? 
It will have it could look like it has a very big mask because internal to the ball, the photons are bouncing around with hot make it have very high energy. the bowl, even though the bowl is just sitting there, the photons inside are bouncing around very high energy, and again, that energy will look like a mass from les MC squared. So it's it's kind of like temperature, right? If you have something that's just sitting there a definite temperature, really what's happening is that there's particles that are moving around inside that object really quickly. so if you had you had a big, you know, if you had this you had this ball with maskless reflective walls and you had high energy photons inside, the mass of that ball would look like the sum of the energies of all the photons inside. 
So if you tried to like take the ball, it would be harder to kick a ball if it had high energy photons in it. than low energy. is an example of mass that has nothing to internal kinetic energy look like the mass of the macroscopic object., and that's exactly what a proton is. So a proton is exactly this, except it's not protons that are around. It's gluons, it's gluons and corks. 
These things are bouncing around, and there's actually no wall, so this wall there's an effective wall here that's just coming from the range of the strong interaction, but there's no there's no there's no reflective wall at all. It's just a strong interaction as keeping it together. So so a proton sitting there in empty space is really corks and guons that are bouncing around interacting with each other, and they have big kinetic energies. 
These particles, while the gluon has no mass, these corks have a very small mass, much smaller than mass the proton, so almost all the mass that the proton comes from internal kinetic energies to the proton. Okay, and that has nothing to do with the Hakespel. That has to do with the strong interaction. 
So if if we lived in a world that had no strong interaction, these these courts would be nastus. The Gulinar is nastless, the proton would still have basically the same nast it has because of the internal connect energies. Okay, so you' read in the in public public literature that the H gives masked all the particles in in the world, that's not not true. 
It gives mass to the electron, but not basically not the nucleus. And remember the nucleus as most of the masss of the of the happens. Okay, so most of the mass in the universe, actually the visible mass will come back this later. 
Most of the visible mass in the universe is in form of a protons or neutrons's is responsible for all the what do we have this theory that can now, it's often said that it can explain how particles can have a mass. I think the right way of saying is it can accommodate maths. And we still don't really know why the Hickfield is on, we're just assuming it's on, but it can accommodate the fact that there is masses. 
And the Hon is needed to to make to keep the theory consistent and but more importantly it's a tracer for these ideals. right? Experimental physicists really like the expos because we don't like this idea of just putting in random fields that you're just making up, okay? So if you put in these random fields, there's a price you have to pay and that price is the Higgs blows on better exist. 
It makes a prediction if exists And so that gives experimental physicist targets. So if we want to kill this idea, we go out and see if there's no Hicks goes on, that idea is dead.? So the Higgs bows on is so important, as a tracer for this crazy ad hoc postori kind of putting things into the theory. 
Okay, and so the question now is, let's assume that the theory is right. What does it predict about the hows on? what can we say about it? 
It turns out we can say a lot about the Hoson just from the fact that you're putting in this putting in this potential that gives the particles mass. Okay? First of all, because the hicks is really just excitations of the condensate, it has to interact with the matter has to interact with matter particles that have nas and force terrier particles have anas just like the condensate does. 
So all its interactions are it have to be identical to the condensate interaction. so that means it have to be interactions that look like this, right where the Higgs particle that can interact with two particles. sound. So it's So if I have um so if I have a if if I have a I think of a spring a string, that that's kind of a a field where you have the string height in every position. You can excite the string by by like plucking it. 
Classically, you can get any any amplitude ways, right? you can make it bigger by hitting it harder or smaller. Upon mechanically, there's the smallest the smallest wiggle in the string and that we call a particle. 
That's and that's the hitsos. So it's basically the smallest vibration of the Hicksfield you can have. And if you have bigger vibrations, there's just more Hosones. 
Yeah, that's a good question. Okay, so it has this new particle that has to interact with with matter particles, so there has to be this interaction of a h particle and two matter particles. And this, so not only does this interaction have to exist, the strength of this interaction has to be directly proportional to the measured mass of these particles. 
If it isn't, it's not going to work, though it'll look like it has the wrong mass. same thing here. the Higgs particle could interact with two bosons and again, this interaction strength we know has to be proportional to the mass of these particles. diagrams, actually, this would be anti. Okay, so it's it's not a just a call, oh yeah, there should be this other particle. No, there should be particle that has welllined interactions and we'action as well. remember, you putantity, you can't have any you want the spin. 
So we know that this particle has to have one of these spins. but let's look at these these these interactions. So here I have I have a the particle, right, the Higgs particle, which at the moment, let's say we don't know anything about it, and here we have two fermons. Right. 
Well, the only one of the only interactions involving fermions were fermont fermion boson. So what that tells us is if we have this interaction, this has to be a boson. Okay? 
Right, this was a consequence of putting together relativity in quant mechanics. You can't have any interactions you any interactions that you want. Most of those interactions are not consistent. inconsistent theories. 
Only if you have fermions interacting in this way. Okay, so that rules out and because we know boszons have to be the inter spins that rules out, spin and half and spin three hours. Okay, Spin two is ruled out as kind of a special case. 
So actually, if you go through the details, Spin two is allowed, but it's just barely allowed. Okay, you can have a spinw particle, but if you have one, you're only allowed to have one spinw particle, and this particle has to look like gravity. Okay? 
It has to couple exactly like gravity to interacts, which is the energies of the particles. Again, this is a this is a big hit because we have um we think we have a graviton in the theory and that would be a spin too particle. We think there's only one one of those. 
So but the Higgsoson cannot be the spin spin particle. Okay, so that only two options at this point could have other two. But if you have a spin one particle, that's kind of the reason we got in this mess to begin with, right? 
Now you're have a spin one particle that has a mass so the Hicks has a mass. it's going to be flipping back and forth, and it's going to be looked like it's losing charge. And you could fix that by getting by adding yet another condensate, you know, like an Alison condensate, okay And I would assume that it has the same crappy potential, right? And there's an Alison, you don't turtles all the way down, let's the sp complicated. it't just be a bunch of them, but let's assume that that's not the case, okay? 
That leaves only a spin zero car. Okay, which kind of the other thing that's kind of interesting is we had never seen a spin particle spin zero particle before. So if you remember the list of all the particles, we had spin, half particles, we had spin one particles. 
We haven't seen the spin two one, but we think there's good reasons for that. We think that's the graviton and the gravity is just so the interaction of gravity so we we can't see it interaction with particles, but we have good reasons to believe that's there. Let's leave us let's meet us on like three half for a second. 
These particles are constrained o so by the way, you're only allowed to have eight, three half particles for when you do the calculation. We haven't seen any of those yet. These particles are you can have as many as you want. okay? 
We have about 10 of the spin one particles. We have 45 spin half articles, if you you know count anti particles and so on. And we saw zero of these before. 
So it's kind of unusual why you would have, you know, again, maybe this is some deep the it's like the periodic, right? You're observing these numbers, maybe this is some telling us something deep, but we had never seen a spin zero particle before, and the theory is kind of predicting that it should be a spent part. Okay, so the only thing that we didn't know that we don't know or we didn't, which we'll talk about later, is the mass of the Higgs particle. 
So that's kind of a free parameter. okay? So the theorest can change the mass, but everything else is fixed. It has to be spin zero. 
Basically, it has to be it goes on, it has to interact with the mass. so on. So again, it's it's you can make this ad hoc assumption, but when you do, it makes very concrete, precisearp predictions about the exposal. Okay, so that's why I feel attractive because you know, if you assume that those those assumptions have consequences. 
Okay, so let's go back back to this statement, so okay, you see this in the press a lot. The Higgs both are dog particle is responsible for all the all the mass and universe. So let's see if we can correct it a little bit. 
First is, has something to do with God, right? This was actually from marketing, there was a pretty famous physicist called named Leon Letterman, who was writing a writing book kind of describing his boson and kind of the science behind trying to find it. This was in the 80s he was doing this. 
He wrote a book about it and he wanted to call it the goddamn particle because it was so goddamn hard to find in the 80s is published and said, no, no, no, no, you can't do that. And they said, hey, Okay, there you go. So he so but his publisher said, no, no, no, he can't say goddamn, but why don't you call it the copartle? 
That will sell more books. So he has this book called a nonparticle and this name somehow on past. for the house. Higgs Higgs it'sible for all masks.? 
It's only responsible for a tiny amount. It's very important, the mass of the electron gives you the size of the atom so it's really important to our everyday lives, but most of the mass is not from the eggs. this is a version of the state. Okay, so yeah, a quick history of kind of this this area of the field would let up to the discovery I think it's horrible. 
Okay, so in in the late 60s is when this really took took its modern form, right? So that's when people got hit to this idea that you have to be conservative, you have to really put take these principles seriously and put them together. And when they did that, they predicted that these particles should have a mass., and then, of course, you know, right after that, you you realize that mass is inconsistent and you need need to fix it. 
But in the 80s, these were they discovered these particles, these mass of WD particles were discovered at term. Okay? So they were using a collider that's very similar to the LHC except lower, uh much lower energy. 
And they so they collided protons, uh actually protons and anti-rotons, so they should be. This is like an upcork and an anti-up work. And there is somebability for producing a Z particle in those collisions and those Z particles can give electron. and electric would be an electron and antilectron. 
And you could see these these were seen at this previous coll. And so they conf the of these particles byucing them directly. Do you directly make them in a collider and use and you observe what they do, how they how they interact or how they decate other particles. 
Okay, and then in the early 90s there was a big program to study these particles. And you're gonna see this repeated. Okay, so, you know, the 80s we discover them. 
Now we have experiments that produce a lot of them and study their properties in detail. Okay? And so this was done this was really a precursor to the LHD. 
It was using the same ring where the LHG says this big, you know, 27 kilometer tunnel, except they were colliding electrons and anti-electrons. they do that you could put it kind of thinking of it going this way. If you have an electron electron, you could make a particle and you could make a lot of them, so in in the 90s, they did this and one of the things that they studied was its mass, so they measured the mass of the particle very precisely. and what's interesting is one of the effects that you can have, again, this comes from the fact that you have antimatter in the theory and we talk about the vacuum having matter and an particles popping in and out of existence. that happens to the Z. So you make a Z, it's coming along, and there's some probability that can turn into other types of particles. Okay, so it could turn into it in this case, it's it's a top quart in an antitop core. 
Okay, and and it can do this very briefly and then come back to the Z, right? Again, this is a kind of a quantum mechanical effect. One of the things that happens is this changes the mass of the Z that you measure. 
And so these type of processes, you know, there's some probability for them to happen, and the effect of them happening is it shifts with the math, the measured mass of the e particle is. you a bunch of them and then you How do they make a good question. experimental but yeah, you could take detail. You basically have fancy cameras to see the electrons and then you can measure their velocities, basically, and you can infer that they came from something that had the right mass. of course, if you're not guaranteed, you know it could be something else that they just have the right mass by chance. And so you worry about signaling background and it's complicated question. 
So this is where the term swag came from, Scientificing, wild ass. Yes, yes. I understand everything else. 
Okay, so this is interesting because I measure this in mass in detail at the time we didn't we haven't discovered the top pork yet. There was some ideas that maybe there was a top pork there, but there was thought to be very heavy. That's why we hadn't seen it yet. 
We didn't have enough energy to produce them directly. But this can affect these higher energy higher mass particles can affect the mass of the, even if you're not producing them directly. so what's interesting about this is you have these from these quantum vacuum fluctuations, or we say quantum loop diagrams because they have a loop in them, you can learn something about the top orp mass by measuring the Zmas. Okay, and that's what you said. 
Okay, so so that happens in the early nineties and then in in 1995 outside of Chicago, we had a Color collider given a precursor the LHC that had enough energy to actually produce these top porks directly and we discovered the top pork. Okay, and what you see in this plot is um is the comparison of these two. So this is the blue is showing the where we thought the top mass was based on these loop diagrams and the makes this pred this prediction is so this is showing that the mass of the top this is 150 times the mass of the proton not so important mass numbers and this is here. 
Okay? And the blue band is getting smaller because we're making more precise measurements. So we're measuring the Z mask better better, and that's allowing us to infer the topart mass better and better. 
And then eventually we discover it directly at the top core and we can measure its mass directly. And what you see is they agree, right? So this here is a big and big verification of this picture that you have these quantum fluctuations happening and there can the value of the top core maps you infer from them is directly consistent with the there's consistently with the one that you directly measure. 
Okay, and so now the same we do the same game again, right? So now we discover the top core, now we're gonna study the top corep mass in detail, and this happens in the 2000s. So at again, mainly at at firmly lab this collider outside of Chicago, you produce a lot of talk works and you could measure its mass in detail. 
And one of the things that the top core can do is it can experience one of these backing fluctuations, but with a Higgs particle. Okay? And so now, if you measure the top quart very precisely, also it turns out that it's going to happen with the W as well, you measure it very precisely, then you can infer what the H's mass should be. 
Even though you haven't scenic directly, you see it's an influence on the nast these other parts. Okay, and that was done and it was again, in the 2000s, it was predicted that the Higgs mass should be kind of somewhere between 50 times itAS the proton and 150 times. Okay, so again, now you have very, very sharp predictions. 
We know all the ways that the Higgs bows are last couple, it has to be a bows on it has to bein zero and we have a good idea of where its mass is as well. It's one of the most massive we've ever seen. only the heavier had this pattern, this pattern of you firstcover something, it tells you about something you don't know about. and you and tells about something you about. we founds so for another, but with this. it was where we found the. Okay., any questions about that?, here. 
So is there any correlation between mass and sun size of the particle? And so we think all of these particles are point like. so they all have no size. And they show up as just pointike. 
They have no no space protons have size because there are there's other you, composite particles. They're made of other things bouncing around, so there's kind of an effective size for a proton, but for the top pork that's hundred times heavier than the proton, we think it has no spatial extent. they hit a black hole hole would have it's We'll come back to black holes uh next week, two weeks. Okay, so how was so how was the hes discovered, okay? 
So again, you know, maybe I'll do another one of these extra series more on the experimental side, the nuts and bolts about how it was how it was done. but but the first order what you do is you get you smash protons together, so you collide prot protons, but whatever, these are really you can think of these as like bags and glueons and quirks. the protons just made of these other particles. so that's what we're colliding, get it very high energies. but we know that the Higgs couples accorded so we have matter particles and protons, so you can imagine these these quarks colliding and making the Hicks particle. right? The problem is this the probability for this to happen at this amplitude depends on the mass of these particles, right? And if you go back back to to this slide that showed the mass, the stuff in the proton is relatively light. right? 
So its interaction strengths are gonna be small. The glueon has no mask, and a lot of the proton is just gluon. They have no mask, and the up and down pork have masses that are you know, one percent the total proton mass. 
OK? So all the things that are all the things that are easy for us to collide like protons are light. Okay? 
That means that they have small mass and that means they have a small interaction, small probability of producing the hs. Okay, really, what you'd want to collide are these particles. You'd want to collide a top cork or these W and the Z particles. 
These have these have masses that are 10,000 times bigger than the WZ, so the probabilities are going to be 10,000 square times bigger. So what's that 10 million times bigger hundred million times bigger than the protons. So we really want to call I these types. 
Okay, so what we really wanted to do is collide two top porks because this interaction would be, you know, get ten to the four times bigger than interaction in protons. same thing or or here. collide andWs. The problem is we don't have top corks sitting around, right? We have to, you know, they are unstable, they don't exist for, you know, finite lifetimes. 
So it's really hard to make a top and WZ collider. So what we have to do is kind of a two-step process. We first have to make the top works, then we have to make them collide. 
Okay? So the ways that we actually produce the hits at the LHC as you collide, you can collide two gluons. These can interact with a quantum lube where you have two top works or a top in an anticop, and then that can turn into a Hicks particle. 
Or so that this one would be called glue on fusion, these fus just kind of jar in terms. Or what you can do is you can have two corks, like an up in the down cork that we have lying around. Those can first create WNZ particles and then those WT particles collide can collide if you do the hits. 
Okay, so it's kind of a two step thing, right? It's because it's more complicated than just the W and the Z, where you can just collide the corks directly, you have to first make these heavy things and the probability to make heavy things as small, and then you have to collide the heavy things. Okay? 
So this is why it was so goddamn hard to find the things. couple couples according to mass, the things that we have in our labs like protons, our weekly are have low masks and so they have weekly coupled to protons. Okay, so this is the reason in the first day, all these numbers were really big. We needed, you know, we needed this huge energy. 
We need to collide, what, 40 million times per second. We had to do that for a number of years. The reason is when you collide protons, most of the time you are not producingiggs because you're not doing these two step things. 
These have a low probability ampllicudes. So we we have to collide a billion protons to get one of these particles. mathematically calculated.. And that was one of the big motivations for getting the funding we had this well defined target Okay, right. 
So this is a deeper answer to whying the difficult. Okay, so I think I'm I'll stop here and there's something like I said, if people are interested, you should let me know and maybe I'll come back into another one of these off the experimental and it looks exactly like it was predicted, right? And again, I think to me many people this is a surprise because this confirms this adoc model, right? 
So it looks like it couples so we see it behave exactly the way that's predicted, it has the rough it has the mouse in the right range. We we look to see if it's behaving in ways that are unpredicted that we haven't seen that happen yet. We've only measured it to like 10, 20 level, so it still could be misbehaving and a level they're smaller than that. and there's only it looks like there's only one of them. 
So there's there these other I should say there's other ways you can you can add multiple h fields. So instead of just having one with a crazy potential, you can have two with the crazy potential. And that works as well. and we'll talk about next next lecture, there's some theories where maybe you want to have two of the the fields, they're more natural in some ways. 
What we're gonna see is there's big so the preview for next week, there's a big problem with the Hick particle the mass that it has. And one of the solutions is having a kind of another form of antimatter. If you had another form of antimatter, you would need an anti- and that would be another. 
We haven't seen that yet. We've only seen more particle and that is kind of putting tension on this other idea of that people have had. talk so what we're talk about next time is the Hicks really now makes leads us yet to another crisis. The prices of where does H mass come from? 
And if you think about if you think about the path of the Hicks, the next thing you'd wanna do is study the haze mass in detail and look for quantumoops or something in the Higgs mass, okay? It turns out those quantum loops predict it should be way, way heavier than would be found. that's that turns out to be crises. Or particles and anti particles in proximity to each other or could they be across the universe? 
So. So you could have so so it's not that every individual particle has an antiparticle. It's every type of particle has an antiparticle. 
So if I have an electron here, it doesn't mean there has to be an anti-lectron associated it. It's just that if there is an electron, if electrons exist, anti electrons must also exists as well. Maybe another way of saying it is kind of an observer dependent, right? 
In some kind of interactions, one observer think it's the interaction of an electron, another observer will see the same thing as an interaction going the other way of a an anti. in this would be. building the detectors to try to find the Higgs particle and doing the data analysis to to discover. Right. So, um for forulaland in Chicago, it's it's uh essentially told department of Energy money almost. 
There' some NSF money, maybe natural science foundation, maybe 10%, but it's mainly by the Department of Energy for it was a relatively low compared to the LAC of SER. So that is about a $10 billion facility that's over maybe 20 years. So it's, it's not a 10 million a year over that period. 
That mainly comes so that the accelerator mainly comes from Europe. So the European. Soern has actually has a treaty where the contributing countries have to pay in a fixed GDP fraction. 
So they have very reliable constant source of funding. The US, of course, it's you know, it depends on every four years prior exch changed. But Sert is able to really execute these long-term plans because of that stable funding. so they they're responsible for the lab and the accelerators. 
Another big cost is the magnets development the bagnets. That's something that the is really good, soula lab works on the magnets, so they contribute contribute, you personnel and development of the magnets. And the detectors the big cameras that are maybe 10% of the total cost.ose are paid for by international collaboration, but the US is like half of that. 
So the pays a big part of those those detectors and they could get made universities tested here and then shipped shipped don't't. I will just say that typically basic science tends to fear better under Republican administrations because the priority is, you know, their idea is that that the government should only find things that the private sector can't, where it when the Democratic administrations, you know, more push to kind of energy and you know, things that are also done in the private program. So usually funding of science goes down overall in republican administrration, but the boost the fundamental science goes up. 
So that's good.. But I mean the other thing is, like in the previous confistration, his presidential budgets were way lower than what they had done previously. The congressional budgets were way above his estimate, and then what ended up getting approved was way above both of them. 
So it was it was kind of all best wrong back then. So. So that's a good question the next cl gonna be linear. 
There's propos to be linear. How do I say this politely? So I think it's a dumb idea to do linear. 
Japan wants to do linear and that's mainly because the country of Japan looks like a line. So the problem with linear is if you want to so if you want to collide, so the next factory would be a quote, Hs factory. The idea would be you we'd go back to colliding electrons and pauseitrons or antilectrons and make cases that way. 
And that's a good way to do it is very clean. When you protons, the pictures get really messy because you have all these corpse and gluelons with electrons and are point like things, so that the collisions are very clean. The problem with the line is if you try to it's very hard to collide electrons. 
So most of the time you try to collide them and they miss, okay? So what's good about a circle is if they miss, they could come back again. You can do it again, right? 
As with a line, you only have one shot. and it's I think it's really just as simple as that. So if you look at if you look at the projections of how good a line would do linear collider would do versus a circular collider, the circular colliders are better because they have higher statistics because they get to reuse the ones that miss. So I think it hasn yet, but the, maybe a hundred kilometer straight line. 
And again that's because you need to get you need to get into um so the way linear is work is like basically like batteries, right? You have a bunch of batteries stuff together and the question is how much energy per meter can you get? So we can only get, you know, like a So if you do the calculation, you need a hundred you basically, you know, tens of kilometers to get the right energy with the technology that we have. 
So they're, yeah, and and it's it hasn't been decided, and these decisions are often made at the political level, right? So it's it's you know, science to say what they want and then, you know, wants to do, you. It's not a good idea… 
It's a right way to think about what's happening, but the last is gonna be much more kind of personal opinion and how I see the and there's not unanity. there's different people think different. So that's just an important with the last lecture. It'll be much more. 
Yeah, I mean well, I was gonna see if if people like this one, then maybe I'll I could do another one.

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