Cari Cesarotti
speaker
212 appearances
1 recordings
1 series
first heard Sep 2024
last heard Sep 2024
Cari Cesarotti’s voice in public audio — every appearance, attributed to the second.
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Appearances
So one of the most fundamental challenges that we would have to overcome if we were to make this amazing new machine would be to accelerate particles that decay, which we have never even tried to do on this kind of scale before.
Yeah, and when you say it like that, not so bad, eh? Just be quick. It's fine.
That's right. Yeah, so this is already hard. So what we would need to do to make all the muons, we produce them as tertiary particles. So usually what would happen is if we have protons.
I know. With protons or electrons, basically you just ionize things, and there's all your particles. They're stable, they're abundant. But with muons, what we do first is we need to accelerate protons to pretty low energies, so order of a couple GeV.
And again, for reference, at the LHC, we collide things at TeV, so 1,000 times lower than what we do at the main collider, but still with some acceleration technology. So we accelerate protons to a couple of GeV, and then we just dump it into some chunk of metal. So sometimes lead, sometimes tungsten. The chunk of metal that we dump into is, in fact, a very sophisticated field of research.
So my apologies to people who work on targetry. But you dump your protons into this material. And then they scatter around and they produce mesons. So mesons are even simpler in some ways than protons. Protons are baryons because they have three quarks. Mesons have a quark and an anti-quark. And they're lighter than baryons most of the time because they're made of less stuff.
So these mesons can be produced. And because they're lighter than the proton, that's usually what... they'll be producing in the scattering process. And you make a ton of mesons in this process. And then the mesons are also unstable. And then they want to decay. So a big way that mesons tend to decay is into muons. Almost primarily, they always decay into muons and a muon neutrino.
And so from there, you have this big cloud of muons that are being produced by this target. But because your protons are slow, particles aren't boosted forward. And because your mesons are even slower than your protons, they're also not very forward. So you have this really huge cloud of muons that are not at all bunched together in the pin-tight way that we would need to collide them.
So that's just the first step. And after this already extremely difficult to engineer and optimize step, you have a something that couldn't even begin to be accelerated. But you have your muons at least.
uh yeah yeah so this is this is something that we do need to worry about because of how tight we need that muon bunch to be um basically because you want to collide it into another bunch and if they're all big and puffy that's never going to happen exactly right it's like colliding if you you like bb pellets right it's like the further away they get the more diffuse they are and the fact that you might collide one bb pellet with another after they travel
some non-trivial distance is getting to be even smaller probability than what's reasonable to expect. So yeah, when you produce the muons like this, of course you get both mu plus and mu minus and you scoop them off into their two different ways to process them. But yeah, once you try to crunch 10 to the 13 muons into a cubic millimeter of space, things start to getting a bit tricky.
Yeah, so this is basically the biggest... open question that we need to resolve as a muon collider collaboration. And so this is called 6D cooling, which sounds very cool. It sounds like you're in higher dimensional space. And really what it means is the sixth dimension is three dimensions for momentum and three dimensions for physical space.
Because you need all these muons to be traveling not only at the same momentum, but also localized to a very small bunch. And so accelerator physicists have been working on this really for 30 years. And they've made a huge amount of progress, certainly in the last 10 years. But basically, what they do is they design these different ways that you have to have this process of
basically taking momentum from the muons because you can't just squeeze them together. It's like squeezing one of those plastic dog toys, right? You squeeze it in one direction, it explodes in another direction. So you need to lose momentum from the system
um and then you can use magnets to crunch it back together so it's this constant process of take momentum give momentum take momentum give momentum um and they need to do that basically a hundred and some times before mu1 even decays and then you need to accelerate it so this is just the process of getting it ready to accelerate you have a millionth of a second and you have a millionth of a second
You would think. But even that's hard. So accelerating particles that decay again are an entirely new challenge. Because one, everything in your detector is being constantly sprayed by the decay products. So there's all these other robust things that you need to account for when you're designing this. And the fact that we don't have the same
We don't have the time effectively to do the same kind of acceleration that we do at the LHC. At the LHC, we just kind of ramp things up and it takes 15 minutes to get those protons up to the speed. We don't have 15 minutes.
We have a microsecond. So the kind of magnetic field that you need to set up to make this feasible is also extremely different.
I love how dramatic we are sometimes.
All right. Well, thanks, Chris, for saying that. Jeez. Yeah. I mean, it really cracks me up because neutrinos, when you talk about them in physics, most of the time it's just kind of like, ah, who cares? Who cares? Neutrinos. They're not going to get in your detector. Don't worry about them.
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