View source for SGU Episode 823

=== Possible New Force <small>(16:38)</small> ===
* [https://theness.com/neurologicablog/index.php/possible-new-force/ Possible New Force]<ref>[https://theness.com/neurologicablog/index.php/possible-new-force/ NeurologicaBlog: Possible New Force]</ref>

'''S:''' All right. Well, me and Bob, we have some really exciting news. I'm just talking about this week. You're going to start us off with the possibility of a new particle or force.

'''E:''' No way.

'''B:''' Yeah, this is over. This is everywhere. I've seen this so many times. Definitely had to talk about this. So potentially big or at least very interesting news from the world of particle physics this past week. Particles called muons have been observed behaving in a way not predicted by the incredibly successful standard model of physics, which you've talked about a lot on the show. Does this mean finally that there's a major update for physics, a major cool new discoveries or perhaps is this just a minor tweak or is this probably nothing? So what's going on? So this comes from Fermilab's long awaited experiments on muons and recently published in the journal Physical Review Letters. Now at a high level, what's happened is scientists have accelerated muons in a magnetic field and the high precision measurements confirm and extend the and greatly refine previous measurements that don't agree with theory. The superficial excitement here, of course, is that this could portend to new physics that could finally give some insights into some of physics biggest mysteries, dark energy, dark matter, combining general relativity and quantum mechanics. I mean, who knows? I mean, that's best case scenarios are very, very exciting. First of all, though, I would like to congratulate the hundreds of scientists all over the world who collaborated on this extraordinary feat. And like for decades, they've been working on this, literally, they've been working on this specific outcome for since the 1990s measuring muons in this way. And it really was a tour de force of awesomeness. So regardless of what happens, bravo, brava to all the men and women who have worked on this. So what are the facts? More specifically, what the hell is a muon? And is it called a muon? Or is it a muon? I think it's pronounced muon. A lot of scientists I listened to the past few days are saying muon. So I will say that.

'''E:''' Is that because of the Greek letter mu?

'''B:''' Yeah. And so, yeah, so I've been calling it muon for God knows how long, but oh well.

'''S:''' So muon?

'''C:''' Muon.

'''S:''' Oh, muon.

'''B:''' Yes.

'''C:''' Muon. Like mew, mew, mew.

'''B:''' So you can think of a muon as essentially a corpulent cousin of an electron. Same thing, but just more massive, like over 200 times as massive. They are truly elementary particles, meaning that there is no internal structure. It's a point particle, unlike an atom or even a proton. They all have internal structure. There's also a third cousin as well, and he or she is called tau. And that's even more massive. She's the most corpulent-licious version of these bad boys. And together they are leptons. They are part of the family of leptons. You may have heard of that. Leptons are fascinating. So there's three. Electron, muon, and tau. And those are the charged leptons. There's three others and they are uncharged. Can you guess what they are? Yes, Bob, you are right. They are the neutrinos. Neutrinos are leptons and very distant third or fourth cousins to electrons and muons and tau particles. And, of course, to fill out the lepton family, you've got to throw in the antiparticles because they're in there. They're in there as well. So now you're probably wondering, well, if these other electron cousins could orbit atoms, like the normal electrons, is that real? Does that happen? Yes, they can. You can have an atom with a tau or muon orbiting instead of a regular electron, but these are exotic atoms, but they are very short-lived. Muons and taus are unstable. They decay into electrons, which fortunately are extremely stable. But yeah, any cool atoms like that, if they are created, don't last beyond microseconds. So that's unfortunate. Or maybe it's fortunate because who knows what kind of weird universe we live in with exotic atoms everywhere. So, okay, kids, it's time to put on our imagination hats. If you want a mental image, think of a muon as a tiny ball of charge that's spinning. And a spinning charge like this behaves very much like a common bar magnet, a straight piece of metal with a red north and a white south on the bottom. I haven't seen one of those in a few dog's ages. Now remember, though, mental images like these can definitely help, but remember, these are imperfect mental analogies, but that's probably the best our baseline human minds can do right now. So, okay, so this is player one. The muon is player number one in this experiment. Muons have a magnetic field and angular momentum. And our limited minds can think of that as spin, like it's often compared to a spinning top or a gyroscope. That's a good way to think about it. See, then after player one, now we've got player number two. And in this experiment, player number two is an intensely controlled external magnetic field that is exposed to and surrounds the muon. So these two guys are kind of like in the same space. The muon with its magnetic field and this external magnetic field. Now when you have, when you introduce this external magnetic field, it causes the two magnetic fields to interact, and that causes the muon spin to process. The spin axis processes, and that's roughly, procession is roughly analogous, again, to the axis of a spinning top moving how it moves in circles. The ends of the axis move in circles. That's a good way to think about it. And it's this procession that is the focus of this experiment. And it's this value that is called the g factor. And that this is what they're trying to calculate or trying to use this, this procession to infer the very extremely precise value of the of the magnetic moment of this muon. So yes, the speed of that procession tells us precisely how strong the muon's magnetic field is. We can then measure the strength and compare it to theory to see if they match. And if they match, then the theory is correct. And that's awesome. We have confirmation of this amazing theory yet again, more confirmation. But if it doesn't match, we may have some new physics. So it's always an interesting possibility. Now there is a third player here making this kind of like a quantum threesome. And these are called virtual particles. We've mentioned this on the show, and I love virtual particles. We know that a vacuum is anything but empty, right? You think the vacuum is the epitome of emptiness. No, not at all. All sorts of particles appear from apparently nothing. But really, it's really they're appearing from the energy inheritance space time itself. They disappear and they appear and disappear too quickly for the universe to really care. But also, some of these particles, some of these virtual particles we can't make in any collider that we have on any drawing board. They are just like too massive. They exist for such a brief period of time, we really can't directly examine them, which is unfortunate, but we can investigate them indirectly.

'''E:''' How do they exist in nature then?

'''B:''' At the quantum level, these virtual particles appear out of nowhere. They kind of you can have a particle and antiparticle appear out of nowhere and then hit each other and annihilate and disappear. So yeah, they pop in and out of existence and they interact. They can interact with particles and this is what's so important in this context. So these virtual particles surround muons. If you could look at a muon, you would just see them all over the place. And they can interact with the muon and have an impact on this G factor. So we have to take that into account. Okay. So all right. We have muons which are revealing to us the exact strength of its magnetic field because of the way an external magnetic field and virtual particles affect its procession. That's the big picture of this.

'''S:''' Bob, do you know what subatomic cows say?

'''B:''' Muons. Good one, Steve. Okay.

'''E:''' We were all thinking that.

'''B:''' So now the standard model though just laughs at all this complexity. It takes into account all of this and predicts a very, very, very specific value for the G factor and it's called G minus two, which is actually the name of this entire experiment. The accuracy of the prediction in the standard model is 400 parts per billion. Very, very accurate. Now the Fermilab Muon G2 experiment is designed to be accurate to only 150 parts per billion. That's like measuring a football field accurate to a tenth the width of the iconic human hair that's always used in these comparisons. So amazingly accurate. When this initial measurement from Fermilab is compared to theory, it does not match. And this is exciting obviously because it means that there could be some unknown virtual particle that smacked the muon in the face and changed its procession in a way that an amazingly accurate landmark theory knows nothing about it. So that's why this has so much potential because this is something that the standard model just has not predicted. So this is why this could be something tiny and insignificant in some ways, but it also could be the other end of the spectrum, something huge and amazing. Fermilab physicist Chris Polly told the New York Times, this is our Mars rover landing moment and Rene Fatemi is a physicist at the University of Kentucky and is also a simulation manager for the Muon G minus two experiment said recently that this is strong evidence that the muon is sensitive to something that is not in our best theory. That's a really good way to put it. And I can't disagree with these scientists, mainly because I'm stupid compared to them, but I can put this in a context that could be that you may find interesting. So as usual, it's premature to celebrate. Do not break out the bubbly for this. I mean, you could do it just for the raw accomplishment itself, but don't start, don't pull out your new particle/new force bubbly. I'm going to wait on that. And that's mainly because of our buddy called Sigma. We've mentioned that on the show many times, experiments, anything that has experiments typically will use Sigma to measure standard deviation, right? And that's used to express how likely is a result. Is it just random chance or what? And the Sigma can really help us wrap our head around it. Now Brookhaven National Laboratory did the very first experiments with G minus two in 2001. I mean, two decades ago, and they found this G factor anomaly. They found this difference between observation and theory. And they calculated Sigma at 3.7, which is it's okay, not anywhere near the gold standard of five Sigma. Now the first result from Fermilab, the thing that we're talking about right now, this is the first result, the initial result from Fermilab that combines with the Brookhaven because they're using most of the same equipment they're using. They actually transported the entire ring to Fermilab. So when you combine the Fermilab results with Brookhaven, it brings it up to 4.2. Now that's 99.7% probably accurate. There's a 97.7% chance that this is real and not just bad luck one in 40,000. That's good, right? That's good. One in 40,000, but that's still nowhere near the gold standard, which is five Sigma. That's one in 3.5 million. So if you're not at five Sigma and you're making a huge claim, well, I'm sorry, talk to me when you get to five Sigma because we cannot assume that this is right even though there's only a one in 40,000 chance that it was a coincidence.

'''S:''' But Bob, let me point out at this point, though, that this assumes that there's no experimental error, right? This is just, if the data is correct, what's the probability that this data was occurred by chance alone, one in 40,000, one in 3.5 million. But this has nothing about there being some systematic error in the experimental setup or the way they're measuring things. So like, for example, I believe if you remember like the faster than light neutrinos, they were up to six Sigma with that. But that doesn't matter because they had a bad cable the Sigma doesn't account for things like, you know.

'''E:''' Yeah, are they trying to falsify the hell out of this thing?

'''S:''' A hardware problem. So it's not just that when we hit five Sigma, it's proven. We also need to replicate this with different equipment in different labs to know that there isn't some systematic problem there.

'''B:''' Right, right. And that's definitely part of the process. And that kind of relates to my next quote by Bruce Shum, he's a professor of physics and he's the author of a popular book on the standard model itself. He said, there's a little bit of skepticism that's been cast on it. When you make a measurement and you compare the expectation based on everything we know, the standard model, there's a little bit of concern that maybe the calculation wasn't done quite right. And yes, the standard model has been amazingly almost unparalleled how successful it's been over decades. I mean, it basically lays out all of the forces and particles that we are aware of in physics and its predictions. I mean, we found the Higgs boson based on purely on theory, on the predictions of the standard model. We knew that it had to be around this energy regime and we found it at the LHC purely because of the standard model. So when you tell me, when you come to me and say, hey, it looks like the standard model got this one bit wrong, and we're at 4.2 sigma, it's like, well, okay, that's great. But you know, chances are, there's probably been a mistake. That's what you got to assume at this point. And sure, look really hard and bring up sigma as high as you can. But until that, until sigma gets really good, then you can't really make too many assumptions because standard models is too amazingly successful to think that it's made some big mistakes here or that there's such an important chunk of it is not there regarding these types of particles and forces. And don't forget, though, Steve, Fermilab has gone over 6% of its experimental results. What we are talking about today is because of its 6% of what it's gone over. So we're going to have to wait a couple of years before it analyses all the data. And maybe they'll shoot what you know, maybe they'll hit five sigma, maybe they'll go to six, who knows, but we're going to have to wait until until that happens. If they do get over well over five sigma, and they still and they could replicate it and all that good and we say, yep, this looks we have to think that this is real, then then that of course, that would be fantastic. And as my my smart friend Leonard Tremille says, he's recently described, he said, when an experiment overturns theory, and that does happen, it has happened in the past, an experiment actually overturns a theory that usually leads to a couple of possibilities. In this case, the overwhelming likelihood is that the standard model would be tweaked, but essentially remains the same. And that would be kind of like a disappointment. But you know, this is what I'm expecting to happen, that they're going to find that you're going to find this particle and force and that a new force, that's a reason to get drunk right there. You find a new particle and force like this, absolutely start drinking. That's wonderful. I mean, Cara will be telling her kids when she's in 80s, like I remember when Bob first talked about this on the show. Absolutely. And that would be great. But there's a much less likely but a very real possibility that this opens up whole new concepts and models for physicists to use to potentially explain things that the standard model definitely cannot deal with, like gravity, like dark matter and how Jay's meatballs can taste so damn good. The standard model goes nowhere near as any of that stuff. And so there's definitely gaps in the standard model that we need theories for that we don't have. So those are the kinds of theories. Those are the kinds of breakthroughs worth waiting for. So keep your eye on this one.

'''E:''' Jay's secret ingredient is muons.

'''B:''' Muon balls.

'''S:''' Yeah. So, I mean, I wouldn't be surprised if we learned that there was some kind of experimental error, a calculation error, like the sort of the way that they're calculating or measuring the result is off. Because this is tricky.

'''E:''' Because it's happened before.

'''S:''' And it's happened so many times before that that's a good first assumption. And then if this is real, I think it's most likely that we're going to get a tweak to the standard model. But the same model is correct as far as it goes, but it's missing a little piece. And I think the major change in fundamental physics is the least like the outcome here. But of course, that would be the most exciting.

'''B:''' And it's still possible. And don't forget, this isn't the first experiment. This is a follow up on the Brookhaven experiment from 2001. And this just refined it and made much more refined results, much better results, still pointing to this anomaly. So that's so that's kind of like a second confirmation here.

'''S:''' Well, that's all exciting, Bob. But I think I may be able to outdo you.

'''B:''' Try.