p->e+pi0 and p->K+nu are the most studied channels in SuperK, and in HyperK in the upcoming future, with more statistics, it's estimated a 3sigma signal significance in 10years HK run. SK ruled out a lot of GUT models, and there still some SUSY GUTs within the sensitivity range of SK, and Hk, a lot of things will come.
Thanks for the info! Althought I'm pretty certain how this is (not) going to turn out and 3 Sigma is... well, 3 Sigma, it seens like pretty cool research.
99.7% of all results should fall within +/- 3 Sigma. Anything outside of that range has a .3% of occurring randomly and may not violate any theories or models. This is why it's important that science tends to go for the 6 sigma with only 3.4 events out of a million that it was a fluke, which for the most part probably means your result implies that your hypothesis (current working theory) needs reworking. To put that into perspective, 3 sigma has 66,807 "flukes" per million. Not a lot, but it's enough to worry people that your data may not actually be outside of current theory. You can see why 6 is the gold standard.
Question: What are these "new theories" and how do they improve the standard model ("best theory ever devised"), respectively, what are the gaps in / the shortcomings of the standard model?
There are many new theories. Tons of them. What they are trying to solve is the nature of dark matter and energy. They are trying to understand why there are quarks and leptons. They are trying to understand why there appear to be a finite number of forces (different people, counting different ways, come up with numbers in the range of 4 - 6 or so). They try to bring gravity into the picture, which is currently not true. They try to understand the nature of matter and energy shortly after the Big Bang. In short, they try to extend our understanding of the laws of nature. We don't understand them all. We've made great progress in the last century, but there is a lot of the way to go.
Sabine’s point (that I happen to agree with) is that these “new theories” aren’t theories at all, because they aren’t a response to observation, but instead are an attempt to create a “more mathematically beautiful” theory than the SM. The reason is that an hypothesis is a response to an observation, and that in explaining the observation it can make predictions about things not yet observed. Think about how GR explained the orbit of Mercury, and the same equations also predicted that light would bend around a gravitational field, which was confirmed during the 1919 Total Solar Eclipse. Various “New Physics” theories aren’t explaining observations that the SM can’t, because SM works great. Rather they are trying to guess what we’ll observe at higher energy levels (or longer timescales) than we can currently generate. This is backwards from the way science usually works. What’s great about this is that when their predictions fail, the theorists can generate another theory and claim that they’re doing science because they moved on when their ideas were falsified. Current results at LHC aren’t too promising for new physics, either. To date, nothing has been unequivocally observed that isn’t handled by SM. But the quest for proton decay will provide grant proposals and publications for a few more years, at least, so there’s that.
@@TheGotoGeek You are mischaracterizing the history. General Relativity was devised as a theory on aesthetic grounds. Only later did it answer the problem of the precession of the orbit of Mercury. In fact, Einstein first miscalculated this problem and only fixed it later. The theory was most certainly not devised to solve this issue. And, on the SM, again I would disagree. The SM does a great job on many things, but there are many questions it doesn't answer. These new theories are all attempts to extend the SM, not on aesthetic grounds, but because those questions need answers. It is true that some theorists use aesthetics to guide their thinking, but what would you have them do? Consult tarot cards? The goal is admirable and you have to try >>something.
The standard model isn't just flat out wrong (the observable universe didn't match the predicted model so they invented unfalsifiable dark matter to rectify. Unscientific!) but it is DESIGNED to be wrong. Human physics was subverted 100 years ago and the why was likely to stop us reaching the stars as a species. If youre a budding physicist. Go back and study pre 1927 classical physics and disregard modern falsehoods like the SM.
This was cutting edge research back in the early 1980s when I was a physics student at the University of Michigan. I think it was Professor Tris Coffin who brought our honors class on a tour of Fermilab in 1983 or 1984. I'm a bit glad they haven't seen any proton decays, but am a bit bewildered by the tweakings of theories. Good you got a new detector for your neutrino line, I remember the 15' deuterium bubble chamber well.
When you say you're a bit bewildered by the tweakings of theories, do you mean you think it would make more sense to conclude that those theories have been experimentally ruled out? Or is it the ways that people have tried to tweak them that doesn't make sense to you?
Fascinating! I do wonder, though, what role the Baryon Number conservation plays in the Standard Model? It just seems arbitrary, like it was devised to "rule out" things that we don't see, but that there isn't really any other good reason to rule out the possibility. If we know that baryons are made of quarks, and we can account for all of those quarks (as you suggested), why is that not a good theory? Have we tried to destroy protons and found that we couldn't? Otherwise, baryon conservation seems like one of those things thought of when protons were thought to be elementary.
My basic understanding comes down to this: Conservation laws are the results of symmetries, as we all know from the very famous Noether's theorem. The theory of strong interactions and it's gauge symmetries are QCD, and QCD of course describes the behavior of quarks and gluons. The equations of QCD are invariant under a global gauge transformation, which gives rise to a conserved quantity. These conserved quantities are simply added degrees of freedom that we assign a name to because we know it is an intrinsic property that is conserved. We assign these names like charm or strangeness or baryon number. In the case of charm and strangeness, these values are conserved in strong interactions (nuclear) but not weak interactions (decay). All of these conserved quantities just give rise to more degrees of freedom, which we call quantum numbers. Other examples of such quantum numbers are mass, electric charge, lepton number, spin, isospin, hypercharge, flavor, parity, helicity, color charge, principle quantum number, magnetic quantum number, total angular momentum, etc etc. Many of these can be broken down into further subcategories. If you ask me, it's a bit confusing and out of hand, but when you take them in one by one they all seem decently well justified. However, I've only got a basic understanding of such things. I am not a nuclear nor particle physicist, just a hobbyist. I hope this helps though. It is worth noting that QCD in particular is quite tricky. The strong force has such a large magnitude that non-perturbative effects may have a major impact on it, so there are many theories that depend on these effects. I've heard of chiral symmetry breaking but unfortunately my knowledge of QCD is pretty limited and I don't understand this enough to explain it. For some more information about this type of thing, look into sphaleron processes. These come from electroweak interactions which have been shown to violate other conserved nuclear quantities, as stated above. Pretty interesting stuff!
When it comes to quarks, there are 2 types of particles. Baryons (which have an odd number of quarks), and Mesons (which have an even number of quarks) (This means that, in general, the Baryon Number of a Baryon is actually [#Quarks - #Antiquarks]/3. So if you had a pentaquark composed of 5 quarks, the baryon number would be 5/3. But for any Meson, which has an even number of quarks, this number is defined to be zero. However, particles with 4-5 or more quarks are exotic particles with extremely short half-lives, so they only show up in particle accelerators. Same thing with single quarks, which we don’t see in nature due to a phenomenon known as color confinement, which arises because of how strong the Strong Force is on small scales. Thus we typically talk about particles containing 2-3 quarks in most scenarios) Anyway, each quark has a spin of +/- 1/2, which leads to why the numerical parity of quarks (even/odd) matters. With an odd number of quarks, you get a half-integer spin (1/2, 3/2, etc…), whereas with an even number of quarks, you get integer spin (0, 1, 2, etc.) As it turns out, this has a huge effect on the way particles behave. You might be familiar with something called the Pauli Exclusion Principle from Chemistry class, which decides how electrons fill the electron orbitals of an atom - each electron takes up a different slot among the possible electron states for that atom. This is precisely because electrons have half-integer spin (they are not composed of quarks, but every fundamental particle will have either integer spin or half-integer spin) Particles with half-integer spin are called Fermions, and follow something called Fermi-Dirac statistics. This is basically a generalization of Pauli’s principle, and it says that 2 Fermions in the same system cannot have the same set of quantum numbers (e.g. with electrons, we have n = 1, 2, 3, …; L = orbital shape = 0, 1, 2, …; m_L = orbital orientation = 0, +/-1, +/-2, …, +/-L; and m_s = spin = +/- 1/2). This tendency for Fermions to “spread out” among all possible quantum states has a huge effect on their observed behavior On the other hand, particles with integer spins are called Bosons. Most of the time we tend to talk about the fundamental Bosons, which are not composed of smaller particles. These are exactly the force-carrying particles in the Standard Model (Photons for Electromagnetism, Gluons for the Strong Force, W and Z Bosons for the Weak Force, and yes… the Higgs Boson, which is how the fundamental particles obtain mass - but it’s not actually a “graviton” for the Gravitational Force, which is outside the standard model) Anyway, we can also talk about composite Bosons as well - anything with an even number of quarks (Meson) will also be a Boson. Ultimately, Bosons follow a completely different set of behavior known as Bose-Einstein statistics. The basic idea is that you can have as many Bosons as you want in the same quantum state, and they are perfectly happy. For instance, this is what allows LASERs (Light Amplification by Stimulated Emission of Radiation - in this case, “radiation” refers to Gamma Radiation, aka Photons) to work. Lasers emit a beam of photons that all have the same exact amount of energy (and therefore the same wavelength), so you obtain an extremely coherent beam of light that is all a single color (unlike a lightbulb in your house, which will actually emit a range of wavelengths across the visible spectrum, but our eyes only see the average color, such as white/yellow/etc. depending on how the bulb is designed) (I believe LASERs operate by what one might call reverse-spectroscopy. Basically, find an atom/molecule that emits a spectral line of the wavelength you want - which occurs via an electron level transition that emits a photon of the required quantum energy - then find a way to make that specific transition happen consistently and repeatedly within a macroscopic amount of that substance) So that’s it. Baryons are Fermions (odd quarks = half-integer spin), whereas Mesons are Bosons (even quarks = integer spin). This gives us some idea at an “intuition” level as to why Baryon Number might be conserved (However, arbitrary Fermions and Bosons are not necessarily conserved. Though it seems like this happens when 2 or more Fermions create a composite Boson - 1/2 + 1/2 = 1 - which would not happen with a possible Proton decay into a smaller particle, for example)
@@Muhahahahaz But was is there to stop let's say... a Proton and a Neutron to change into 3 pions? we have 3 up and 3 down quarks in each system and the second system has less mass.... But the baryon number (which is not a property of fundamental particles) isn't the same.... I also find it fascinating that the standard model predicted the existence of the Higgs Boson to explain how particles obtain mass but as far as I know the other properties of fundamental particles (spin and charge?) are not explained through other particles.
@@Muhahahahaz Technically, a pentaquark would consist of four quarks and one anti-quark; so the baryon number is still 1. With five quarks it wouldn't have been possible for the particle to be color-neutral.
I am a big fan of Dr. Don. Watched his presentation style improve gradually over the years, I admire the persistence and of course the informative videos.
For people asking about Sabine's video, here's the reason why people want extensions of the Standard Model: 1) The SM can't explain the imbalance of matter vs antimatter, why there seems to be exactly 3 generations of particles, as well as stuff like the mass of neutrinos. 2) The SM is known to fail, albeit at scales far, _far_ greater than anything we've been able to probe. It's _possible_ we won't find anything until we get a collider the size of Jupiter but we don't know that for sure. 3) The SM has no underlying explanation of _why_ it is the way it is. It's just a bunch of facts about the universe that have no underlying explanation. That's never been good enough, and every time we've ever gone "that's it that's all there is to it we know how the universe works now" we've been wrong. 4) Even if it's not about breaking the SM, isn't it good and worthwhile to refine it, figure out exactly what experimental parameters we need? More precision in fundamental knowledge is always good in and of itself.
The day has only 24 hours and at some point we need to stop and ask where we should be better be spending our research time and money. Do we just keep on building bigger tanks of water?
@@spaceman4286 The one thing we don't know much about is neutrinos. And Fermilab is not a tank of water. And the other experiments were not designed to specifically look for proton decay. And for neutrinos, yes we are probably going to keep building bigger tanks of 'whatever' because they are the biggest unknown right now.
I don't know about the rest, but concerning point 3) she talked about it. Basically, there is no need to ask for why things are, some things just are and there is no way to really "explain" it, like constants of nature. Knowing why things are the way they are is only useful if it helps make predictions, as long as we can predict with perfect accuracy what a blackbox is doing we don't really need to invest the huge amounts of work and ressources figuring out how that blackbox internally works, if such an explaination even exist. I'm not a physicists, but it really seems like particle physicists are sort of just randomly making theories and then try figuring out how to create the observations that require their theories.
@@JohnDoe-jp4em the vast VAST majority of times people in history have said "some things just are and there is no explaining _why_ they are", 100 years later someone had found the explanation as to why they are. "Oh why do chemicals react the way they do? Idk, they just are! We can describe the patterns pretty well, though, so that's good enough" until oh hey there are these things called electrons and they explain how chemicals interact. Until we figure out all of it, yes _all_ of it, it's worth keeping investigating. And that's a pursuit that will never end, because that's what science is about. Pursuing knowledge and answers. As for "sort of just randomly making theories", they aren't randomly making them, they are looking at existing patterns and asking themselves why this part of physics follows different patterns than this other kind of physics, and asking mathematicians "hey do these patterns ring a bell? Is there any logical relationship between pattern X and pattern Y?" And when mathematicians go "oh actually there is! They're both aspects of a bigger pattern, XYZ", physicists go "okay that's certainly a possibility worth exploring!" and they look for pattern Z and then don't find it, and go "hmm, okay, that was wrong, strange how we get X and Y in the universe but not Z, I wonder why" and so on. That's worked for physicists before, and it's actually exactly how the quark model was discovered, and honestly it's the best way we know of to come up with deeper explanations.
@@ericvilas Without knowing that electrons and orbitals exist you would have an extremely hard time predicting chemical reactions. The only way you could predict something would be to record what happened and did the exact same thing again. Yeah it would be cool if we knew absolutely everything but that's both not possible and an extremely wasteful goal to pursue. It's not worthwile to dumb billions of dollars into experiments that are a shot in the dark whether they will even turn up anything useful or just "guess we need to look harder". Prioritization needs to happen, there is a finite amount of money and workforces available and it's not smart to use a large chunk of it to try to randomly guess theories that are not even required to explain an existing observation. It seems kinda true that particle physics is not really productive when despite access to the most expensive toys in science there are no new major advances in 11 years.
Thank you for a presentation that acknowledges things are much more complicated, while sticking to the relevant bits. It's a great jumping-off point for digging deeper into these issues for laymen like me.
@@annaclarafenyo8185 Are you referring to the 1H segment before the intro? When someone says "You know, hydrogen is all around the Universe since forever!" you don't automatically question "define all H isotopes, all around and Universe". C'mon, even chatbots from 1997 were smarter than this...
@@johngrey5806 God forbid someone not being an English native! Aliás, aposto que meu latim enferrujado que aprendi há 30 anos é melhor que seu inglês nativo.
So amazing. Until you mentioned it, I never thought about how long atoms lived, considering the current law of conservation of energy. Great topic, and thank you.
How about a discussion on what CAUSES stable particles to decay??? We know the proton's charge relationship with the background scalar field pressure CAN be modified by use of high-intensity canceling MD & EM fields surround the proton to be affected; hence affecting it's self-stability. This mechanism operates by modifying the local refractive index of the vacuum within the interfering wave cross-section, and has tremendous implications far beyond the scope of this video!
She speaks truth. After Einstein years nothing much is achieved in Physics. All the work is derivative of work done by Einstein and other greats like Schrodinger, Dirac etc.
Baryons do not "consist of 3 quarks". These are the valence quarks, but there are also sea quarks and gluons. Moreover the Standard Model does allow for baryon number violation, only the difference between baryon number and lepton number is strictly conserved, as a global symmetry. However, the SM proton decay is extremely slow, and therefore not observed.
I'm sure he just simplified the description in the video because that wasn't the main point (and the 3-quark model is pretty much any physicist's first-approximation to describing a proton), but I would love it if he made a video discussing the quark/gluon sea inside of protons and neutrons. PBS spacetime recently made a video discussing this in some detail.
Has an anti-neutron ever been observed decaying into an anti-proton, positron, and electron neutrino? I'm not saying an anti-neutron would decay differently, just that I know these kinds of interactions are desirable to observe in antimatter
I reckon that such a reaction would be difficult to observe. Because I don't really have a box of anti-neutrons in my backyard. How do you make anti-neutrons anyway? In high-energy nuclear reactions. It follows that the resulting particles will usually propagate at a speed close to the speed of light. Plus, how do you control the movement of particles? With electromagnetic fields. But there's a difficulty that anti-neutrons are electrically neutral (though neutrons - and it follows that also anti-neutrons - are known to have magnetic properties due to being composed of quarks). Finally, what's the average lifetime of a free neutron? Almost 15 minutes (that's nearly an eternity in particle physics). So good luck holding an anti-neutron for a period of a number of minutes without it annihilating with ordinary matter.
@@xochitlpauli5622 It's not. Protons and neutrons consist of quarks; antiprotons and antineutrons consist of antiquarks. (There do exist baryons [as opposed to antibaryons] with charge -1, but they consist of three quarks with charge -1/3 and are unstable. There also exist unstable baryons with charge +2, consisting of three quarks with charge 2/3.)
@@rodocar2736 Do you have a link to a paper about this observation? Because I tried to search for it, but only found searches for neutron-antineutron oscillations.
Hey Doc Don! I'd love to see a retort to Sabine Hossenfelder's video expressing her frustration with Particle Physics and Particle Physicists. You seem like the perfect person to refute her claims. Either way, it would be great to hear from both sides.
Well, there's actually nothing to refute in her claims. They're not saying anything in conflict with each other. Standard model predicts, that protons do not decay. And this is actually what we are observing. But there are physicists who don't like some properties of the standard model, so they're trying to create new theories that address those properties of standard model that they don't like. These new theories make predictions such as the fact that protons do decay. This much is said even in this video, even in videos by Sabine Hossenfelder. The only difference is, if this experiment doesn't find the proton decay, these guys will just apply for funding of building an even larger experiment, because the current experiment can only find proton decay if it happens after certain long value, but this experiment (and in fact no experiment) will not rule out the chance that proton decay occurs but it's even more rare. This is called a black swan problem. No matter how many white swans you have seen without ever observing even a one black swan, you can't rule out the existence of a black swan and say all swans are white. Same way, particle physicists cannot rule out, that proton decay might be occurring in ranges they have not yet experimented with. They can only rule out that it occurs in the ranges that they have experimented with. And this is what they could keep doing very hypothetically infinitely long. We didn't detect anything in this range? Doesn't matter, let's look for it at even larger scale. Sabine thinks, this is waste of money and you're not going to find new science this way, because if Standard Model is right and there's really no proton decay, then it doesn't matter how large of an experiment you build, you will never detect any proton decay. So now we have to come back to the question, if standard model doesn't predict proton decay, why do physicists even try to look for it? Because they want to see if their theories, that are addressing some things they don't like about standard model, are correct. But is there actually any good reason to invest money into these new theories? Sabine argues, that no, because these new theories are not really necessary to explain any observation that we have made so far. There are things that the standard model actually can't explain very well, but most physicists are not even trying to address those problems, they instead focus on what kind of numbers they have to plug into equations so that the models make good predictions. In case of standard model, they have to put numbers, that have precision of many decimal places and it's not a simple 1 or a 0. So they are creating mathematical models, where there would be nice round values, which looks better on the paper, but actually doesn't describe any currently observed and unexplained phenomenon. So it's a waste of time and money, argues Sabine. These guys argue, that well, they're looking for something and if they find it, it would be a great shift if physics and if not, no harm done. They don't necessarily agree, that money or time should be the limiting factor on what science experiments will be carried out. We should ideally do all experiments possible, they would probably argue. But of course we have finite resources, so.... But imagine you're a particle physicist and your livelihood depends on being able to perform some experiments, but you have no idea what kind of experiments to perform, because standard model is already covered by experiments and there's no low hanging fruit within the realm of properly addressing issues in the standard model, so it would be hard to get funding for that. You see how these physicists are motivated to keep working on easier problems that will get money.
That would be a great idea, Sabine is incredibly brave to poke the Big Physics bear and Don is someone who could sympathetically argue the inside view in a way that would be comprehensible to the rest of us. These two presenters are giants of making Physics accessible.
Hi Dr. Lincoln! I wish you had talked about the specific ways conservation laws might be relaxed in theories beyond the Standard Model. For example, protons might decay into specific particles because while baryon number isn't conserved, certain _combinations_ of baryon number and lepton number are conserved, and that's what would need to happen for the decay to happen.
Baryon number is not conserved even in the standard model, it is violated non-perturbatively by an SU(2) Instanton. This process is impossible to practically observe, but it does happen eventually. Only B-L (Baryon minus Lepton number) is preserved in the SM.
"they made a prediction about this alternative theory. It did not succeed, so we need a bigger test setup". Sabine is fuming right now! She may even decay ;-)
Except in this case, Fermilab constructed the "bigger" test setup for a completely different purpose, and is piggybacking the proton decay experiment on to of it. Assuming she approves of the main use of the equipment, this is the type of thing she'd probably approve of. I would like to see Sabine debating her problem with "big science" with someone who disagrees with her, not least because I want to hear what she says we should be doing instead.
@@EnglishMike Yeah, I'm glad DUNE had other purposes and that proton decay _might_ be a side effect they can look for. As far as Sabine is concerned, I treat her like Neal deGrasse Tyson and respect their expertise in their own fields but when they talk about something outside of that I look for experts in the field they are discussing for verification.
Could you observe other types of baryons to determine if they ever decay into a manner which doesn't conserve baryon number. Other baryons decay very rapidly so they would be a large number of decays rather than waiting on proton decay. The failure to observe a violation of baryon conservation would give strong evidence (although not 100% proof) of proton stability.
You can. We do. And they don't. Baryon number is 100%conserved in all observed decays. I believe that is actually the original reason for its introduction. It was observed to be conserved. Though now, as far as I understand, it is based on some symmetry of the model.
The conservation of baryon number is only approximate. That is, there are situations in which it does not hold. It does not arise from an underlying symmetry following Noether's theorem.
@@michaelsommers2356 An excellent reference, but the first pages say lots of "If baryon number is an approximate symmetry," suggesting that there is some question. In addition, a (very, very) quick perusal of the paper suggests that it is pointing out that the symmetry could be broken in different theories. In short, isn't the paper trying to motivate extensions of the SM in which baryon conservation is broken? If so, then we'd see baryon number violating decays, which we don't. That said, we do look, essentially to find out if the "If" of this paper is real. This was kind of the point of the video. One thing on which I am sure we would agree is that theorists are clever and can often develop theories which violate symmetries that are incorporated in existing theory. Finding those violations is an excellent way to find clues about new physics.
Because Grand Unified Theories imply that leptons and quarks are connected, meaning that the only true conserved quantity has to be the difference between lepton and baryon number (B-L).
- neutral + Charges cancel each other Electrons (-) Protons (+) Neutrons Neutral Transfer of charge As above so below... This applies to so many levels
This is an excellent example of why science is the gift that keeps on giving. Assuming one sees new fascinating questions as a gift. Proton + electron + energy to smash them together = neutron. Makes sense total sense; a neutral particle made by the combination of + and - charges and slightly heavier than a proton because it also includes an electron. Neutron decay = proton, electron, released energy *and an anti-neutrino?* New gifts: Where the hell did that come from? Does the decay create antimatter or was the antimatter created in the fusion of protons/electrons?
Q: Is there any predictions that the standard model predicts that are inconsistent with experimental data? Or does it make predicitons that cannot be correct (ie prediction would break other known laws) If the answer to both is none why are people trying to 'reinvent' the standard model? I'm just confused why anyone would suggest alternatives to a model that has not been proven to have inconsistencies/make predictions not fitting the known data.
They look for a better model because, even if the current model contains no inconsistencies, it doesn't explain everything. It says nothing about quantum gravity, for instance. It doesn't say what dark matter is.
It's a model. That's the simple answer. It's a simplification of what we can observe. As long as we don't know the full extent to which every known phenomena works we can't be sure of anything. In the same way Newton's theories work, they break down at a certain point.
Sabine's take in what Particle Physicists do nowadays is to me the most concise and close to the truth. The field has gotten so big that now it feeds itself, and different thinking is not encouraged: ruclips.net/video/lu4mH3Hmw2o/видео.html
@@michaelsommers2356 We saw that in large scale GR doesn't work and we assumed that is because we are missing matter but we shouldn't rule out GR is wrong too.
Question for anyone: Given the theoretically-predicted 10^31 yrs lifespan of the proton... What size would a detector monitoring vacuum space have to be, in order to expect to find a single instance of proton decay within a ten year span?
You need a medium for the decay products to interact with to detect a result. I’m guessing the because of Argon’s atomic density it’s a “bigger” target chance for a decay product to run into and interact with.
Can you explain where baryon number comes from? At the surface it seems pretty arbitrary to say that proton and neutron are +1, their antiparticles are -1 and everything else is 0. Where does it come from, and, most importantly, why should it be conserved?
The conservation is due to "U(1)v global symmetry of the QCD Lagrangian". Not helpful I know, but the standard model is described by math and the conservation laws are consequences of the mathematics. Think of an interaction as equations with the original particles on the left, and the resulting particles on the right. On the left hand side you have a certain number of equations describing the quarks inside a baryon, and on the right hand side you need another 3 matching equations to describe the resulting baryons after the interaction. A new model, usually called GUTs (Grand Unified Theories), could have different symmetries that change those equations so that one of the baryons is converted into a lepton (eg. the positron) so that the right hand side of the equation only needs 2 equations to describe the baryons, although I know nothing about the GUT theories so I don't know the exact mechanism of the equations.
“Baryon # conservation” is really is really just a consequence of “quark # conservation”. Basically, no known physics exists that can transmute a quark into a lepton, or vice versa. And “baryons” are just combos of multiple quarks, so any reaction or event that starts with N quarks must end with N quarks. However, matter-antimatter pairs of quarks and leptons can be created from pure energy or annihilate back to energy, so to handle those cases “N” is really (#matter quarks) - (#antimatter quarks). That’s why the math to model this underlying conservation law assigns +1 for matter quarks and -1 for antimatter ones, which turns the pairs into 0s. “Lepton #” and “lepton # conservation” are literally the exact same thing, only for leptons like neutrinos and electrons rather than quarks. And all of it arises from one simple, mysterious observational fact: Matter seems to come in 2 types, “quarks” and “leptons”, and we’ve yet to observe any force capable of turning a quark into an electron or vice versa. AFAIK there is no known deeper principle. It’s not like conservation of energy or momentum, where physics obeying symmetries in space and time leads directly (mathematically) to the resulting conservation law in any equations modeling it. These #s are conserved simply because no known particle interaction breaks them, and therefore the Standard Model’s equations (which model such interactions) always conserve them. That’s one reason new physics that “broke” lepton and quark # conservation would be way less shocking than, say, a violation of momentum conservation.
Thanks to Dr. Don, Your explanation is always on next level, simple yet perfect I was wondering if you could let me know how to calculate the mixing angle and construction of PMNS matrix
So, what would then happen to the daughter pion? As I understand it, pions are exchanged by nucleons as strong nuclear force interactions. Since this is an extremely short-ranged force, wouldn't pions be unstable outside the nucleus?
@@narfwhals7843 So what happens to the baryon number it carries? I understood that conservation of the proton's baryon number is why the meson is needed in the interaction.
Things physicists say: "The previous theory stated that the half life was like 20 orders of magnitudes longer than the age of the universe, but it seems that it doesn't decay that QUICKLY after all..."
It can, improving the knowledge on particle physics is crucial for better understanding of how matter works, and discovering new ways of using it properties. (We can see it clearly on how our understanding on quantum electrodynamics improved chemistry and semicondutor/computer sciences). Science isn't a waste, it's an investment.
Thank you very much. In p^+ --> K^+ (u sbar) + nu, is the nu (neutrino) actually a nubar (antineutrino), so you are looking for conservation of B - L? Which (anti)neutrino flavor(s) are you looking for?
So if decay products have to conserve the baryon number and since protons are the lightest Baryon... When you smash 2 protons together there still has to be 2 protons in the debris, that says to me that all other particles are created from the energy of the collision. Unless there is a baryon lighter than a proton that we haven't ever seen yet. Also can protons be annihilated (without an antiproton collison, we know antiprotons have -1 baryon number so the baryon count is zero after such a collision) and what happens to their baryon number if they can be annihilated by any other means`?
A collision is not a decay. There is additional energy. So the debris can include _heavier_ baryons, like neutrons. What would a annihilate a proton if not an antiproton?
@@narfwhals7843 Any collision with enough energy to overcome the strong nuclear force theoretically could annihilate a proton. But there is still a lot we don't know, like what happens if the strong force is overcome. Quarks theoretically can't exist alone so would they decay or would the proton reform from the free quarks? Or would that much energy create some exotic superheavy particles or change the flavor of the quarks?
Don, we are told that protons are made of two Up and one Down quark. The neutron is made of two Down and one Up quark. Also, we are told that a neutron star is formed when electrons are forced into the nucleus and convert the protons into neutrons. How can an electron change an Up quark into a Down quark, and why does an electron not affect the neutrons? Also, we are told that heavy elements are formed from the debris when two neutron stars collide. How are protons formed from the neutrons, and in the exact number needed to form each heavy element?
Up quark has a charge of +2/3. Down quark has a charge of -1/3. The W boson has a plus or minus charge. In the case of neutron decay, d (-1/3) -> u(+2/3) + W(-1). The W then decays into and electron and antimatter electron neutrino. The opposite can be true, too. Shove an electron into an up quark and it can become a down quark. That takes energy, which is given by gravity as it squeezes the star.
@@MusicalRaichu I started to read it, and quickly found more questions. A google search for answers produced more questions. I think it will take the rest of my life to understand the answers to my questions, but I'm afraid I may not live that long.
Since electrons have mass their movement can be restricted by gravity, something a neutron star has so much of that it can overcome Electron Degenerate Pressure (electrons not wanting to be in the same place at once) This means multiple electrons can exist in the same place at the same time inside a neutron star. The electrons are still 'there' however they are no longer individually taking up any volume as they do in normal matter. The space a neutron star takes up is just the volume of protons but their charge is being canceled out by a cloud of super positioned electrons. In all honesty it is better to think of a neutron as an exotic atom between a proton and a electron in essentially all scenarios. Quark theory is great and all but its more math than actual physics 🙃
0:00: 🔬 The stability of protons and electrons is important for understanding the laws of nature and the future evolution of the universe. 2:37: 🔬 Einstein's equation relates energy and mass, while baryon number represents the number of quarks in a particle. 5:25: 🔬 The proton is the lightest baryon and any proton decay would have to conserve electric charge, energy, and baryon number. 8:00: ⏳ The predicted lifetime of a proton is much longer than the age of the universe, but some protons will decay early due to statistical processes. 10:44: 🔬 The DUNE experiment is looking for proton decay and has a high sensitivity to positively charged mesons and neutrinos. Recap by Tammy AI
@@-dennis3755 yeah. I guess. I still feel like we could and should do better in deciding what experiments to do and which not to do. But Fermilab looks overall promising to me. Let's see.
Thankyou. Some issues to consider; protons only make a tiny proportion of the universe's energy, perhaps just 2%. What protons do exist are being continually crushed out of existence in vast numbers in black holes and neutron stars. While they may not decay quickly, overall, the outlook for proton durability doesn't look very good.
This confused me too. In PET scanning (positron emission tomography), the positrons come from protons in a radioisotope nucleus emitting a positron (and a neutrino) and turning into a neutron. This is beta+ decay. It was otherwise a great video, but how this situation is different should have been addressed.
@@stevendzik7312 I think they are talking about proton decay wih no external energy input. Beta+ decay requires energy input as the results have more mass.
Had me confused for a minute since beta+ decay is a thing (proton decays to a neutron and steps down 1 on the periodic table), but then I caught on to the fact you were talking about isolated protons. For anyone else who might have missed that bit, beta+ decay only happens in a nucleus not in a lonely proton, conservations are maintained.
Did Sabine criticize experiments that attempt to falsify the Standard Model? I thought she criticizes theoretical physicists whose theories are either (1) unfalsifiable or (2) uglified after earlier, more elegant versions were falsified.
@@brothermine2292 She also talked about things like that I dont remember for sure but maybe exactly on the proton decay problem too. They just move the time it takes for a proton to decay longer and longer in those theories.
@@brothermine2292 She criticized that particle physicists create theories, then create experiments afterwards to create the observations that require that theory. And if the observations don't happen, the theory gets adjusted to require an even larger experiment to falsify. In that way those theories aren't really falsifiable, because scientists spend their time crafting theories that are always outside of the capabilities for falsification. Theories that might be true, but don't predict anything better than other theories and are too expensive and time consuming to falsify are kinda worthless, because you can create an infinite amount of theories like that which are all equally valid.
New question. Since protons are big bang energy condensed, can we reverse the process and get all proton energy? Whats the problem to achieve this energy?
What about if the Proton's decay scheme is similar to a Neutron's decay scheme, ie, a neutron when it is not bound into a nucleus has a half life of 12 minutes (when bound, it's relatively stable -- ie, you have a stable nucleus, not an isotope that will decay), what if the proton is the same? While bound in a nucleus the proton is stable, but only when not bound in a nucleus, it can then decay.
An interesting idea, but since most Hydrogen is just a proton in the nucleus and its ionization energy is low enough for us to be able to get rid of its electron fairly easily, you'd think someone would have noticed if something happened.
Am I the only one who, whenever he hears about “conservation of energy”, instantly pictures Nick Lucid’s “conservation of energy shall not be violated!!!” Meme?😂
And can you please explain the concept of point masses like electron's physical size and also how long or small a photon is? I mean we say its stretched by redshift or space expansion incase of cmbr and we say photons are quantized so they must have finite dimensions?
Quantization is a commonly misunderstood concept. (Quantum Physics is one of the many, many, maybe even majority of things in science that is very poorly named.) To the best of our ability to tell, the universe _is_ analog, not quantized. Certain things are quantized, not because the nature of reality is somehow digital or quantum, but because certain things in very specific situations are. For example, a free electron can have any kinetic energy, no quantization needed. An electron _bound in a hydrogen atom_ on the other hand, can only have certain very specific, quantized energy states. It's loosely analogous to a guitar string. Free, on its own, the string can move however it wants. _Mounted on a guitar_ on the other hand, it is constrained at both ends, and can therefore only vibrate at the frequencies dictated by those constraints-by the tuning tension and the current fret it's being held against. Since light is created by the change in energy state of charged particles (mostly electrons), and electrons are mostly bound in atoms (it's a very specific state, but an overwhelmingly common one, heh), it's very _common_ for a given photon to have an energy/wavelength of very specific values... but it's not _necessary._ If you want to know more, especially about the sizes of particles, I'd highly recommend Dr. Sean Carroll's "Big Ideas" series. It's basically a crash course in the whole of what's firmly "known" in fundamental physics that he made during lockdown, covering basically everything we know about how the universe works at a level somewhere in between normal layperson pop-sci communication, and what you'd learn studying it in university. It includes this topic, but I don't know that I'd recommend just watching that one episode, as there's a lot of context you might be missing. _Unfortunately_ this is one of those topics that might be a little _too_ involved for Dr. Lincoln's style of video. I'm not sure if it can be covered in 10-20 minutes... but maybe. He's very good at breaking complex stuff into bite-sized chunks, after all! In short, though, to even begin talking about it, you have to get very specific about what you _mean_ by "size" at that scale. If what you mean is functional, viable assumptions to be able to do theoretical work, then we can pretty safely assume in almost all circumstances that electrons are point particles. If what you mean is what we can actually _measure_ (in principle), then interactions between the method of measurement and the particle become highly non-trivial. Meaning as you narrow in closer and closer to the levels of probing energy that are capable of _resolving_ something as small as an electron, your probe also has enough energy to _change_ it, to create a sea of virtual particles near it that make it "fuzzy" in a sense; not in the sense of the image through a lense that's not focused right being "blurry", rather the electron _itself_ ceases to even _have_ a well-defined "size". Not coincidentally, this uncertainty in its determinable, measurable size fits nice and neatly into what is predicted by the Uncertainty Principle. Actually, in a way, it _is_ sort of like resolving images... though not through a normal lens, by being out of focus, but rather through a telescope, by being at the diffraction limit. We're not _there_ yet, with electrons... but we have placed constraints on their size. IIRC, our current constraint says that electrons can be _no bigger_ than about 10^-18 meters, or an attometer.
Light is a 2 dimensional wavelet as it can only oscillate in a single plane & is locked at the speed of light. The size of its existence in a plane is dictated by its wavelength.
Dear Dr. Lincoln, Regarding the possible decay products of the proton in this illustrated example, wouldn't the proton also create an electron-neutrino along with positron and neutral pi-meson? I'd really appreciate your thoughts regarding it. And, thank you for an engaging explanation!
That particular class of proton decay requires the hypothetical X boson to allow violation of the baryon number, converting a quark into the positron, which involves no neutrino emission.
I don't know anything about how this Proton decay will be registered or measured, but if it's such a rare event, will you be sure if you think you found one? Hoe many positive detections do you need before your conclusion is statistically significant?
A lot. But not an unfathomable amount. IIRC, we only have enough detections at the moment for a 3-sigma result. That means that there's a 99.7% chance that the detections are genuinely of proton decay and a 0.3% chance that we're detecting something else, or random noise. Typically in fundamental physics, we don't consider something "discovered" until it passes the 5-sigma threshold (99.99994% vs 0.00006%). Also, only one facility has made the 3-sigma detections, and a discovery requires that at least two independent projects get to 5-sigma. So... it's a ways off, yet; we'd need at least one more completely independent facility to make at least 5,000 times more detections than the first facility currently boasts, but that's not outside the realm of achievability at all. More, and bigger, facilities are under construction right now to try to do just that. In other words, the detections are promising and intriguing enough to compel people to throw a lot more money at it to find out if it's real or not, where before, only modest amounts of money were thrown at the hypothetical possibility. Essentially, proton decay, today, is pretty much where the Higgs Boson was in 1995. Getting a confirmed result, positive or negative, by sometime in the 2040's, is therefore worth hoping for.
@@martinklein9489 Yeah, but from what I think it says in the video, proton decay is even more rare. How many do they expect to find in an hour or ... a year? Let's hope the scientist on duty wasn't blinking or having a smoke break when it finally happens.
I just came from Sabines video about particle physicists. It's changed how I viewed this video tbh, not completely but still, there's a lot to think about here that isn't just the physics.
Proton decay could mean that protons and electrons can arrise from quantum fluctuations without the antimatter counterpart, which would explain why we can't find antimatter in today's universe (in equal amounts as matter)
I love how quantum/particle physics explains natural behavior in terms of the conservation of a quantum property. As if that is an explanation. That's merely a description of "what" is happening, with no details of "how".
What if energy is added to the proton so that it could decay into something heavier? Like a neutron or one of those other baryons that were mentioned but not described at least by timestamp 9:59? Or if energy is needed to make a proton decay, is that no longer considered decay?
It is no longer considered spontaneous decay. What you describe happens in beta plus decay of atoms, where the proton takes energy from the interaction with the surrounding protons and neutrons.
Given that dark energy is associated with negative mass, shouldn’t a proton decay into a neutron and some dark energy particles be allowed in the standard model? What does that tell us about dark energy since we have never detected proton decay? I assume it at least puts some constraints on dark energy?
I assume if new experiment is not detecting decay you will again increase predicted decay time and start building even bigger detector. But is it justified providing that there is theory that does not need protons decay?
I use this topic as a bonus problem in the intro to particle physics section of my class. I give them the Feynman diagram and ask them some questions about it like what conservation laws are violated, is the X or Y boson charged? If so what’s its charge? Etc.
How is baryon number conserved during proton on proton collisions? Are mesons and anti-mesons created during the collision, thus conserving baryon number?
Isn't this like saying "if we find ghosts it would revolutionize our understanding of the world, and we would need to rewrite the entire periodic table". And then use tons of money looking for ghosts finding machine? First step should be to have any reason to believe ghosts exist in the first place, then start looking for ghosts. If there isn't any reason to think proton decays, and our theories also predicts it doesn't decay, and one has spent tons of money checking that it doesn't decay - then maybe it just doesn't decay. Until we have a real observational reason to believe it decays, then maybe move on to something more useful science?
I don't think so. A bigger machine incorporates more events, that's the key. At some point you have considered enough events to make a decision. So far the detectors have not been of a size to make a decision. So bigger than what we have, but only because we have not gone big enough for proof.
@@fps079 - but there is nothing in our theories saying protons does decay, no is there? First you need an observation that can better be explained by proton decay, than not. Then you check. You don't start postulating that "if protons decay then cool". Its the same as saying "we've not looked for ghosts on the back-side of Jupiter, we should build a billion dollar probe to check". And when it doesn't find it, just say "we've not looked for ghosts on the back-side of Saturn, we should build a multi-billion dollar probe to check".
You should mention that it is "isolated" protons that are stable. Protons inside larger atoms are known to decay.
But then it's not really the proton decaying, but the whole atom (atomic nucleus) decaying.
I'm so glad to live in an era when I can watch these videos and be amazed at how much we know and how little we know at the same time.
For every question answered two more questions arise.
Einstein " The more I know the more I realise how little I know."@@malcolmabram2957
@@malcolmabram2957 - Two more? How about at least dozens more 😉
Petition to change the saying, "Watching paint dry" to "Watching protons decay"
i dare not to change that stable number 30
Proton: Mom, can I have instability?
Mom: No we have instability at home.
Instability at home:
p->e+pi0 and p->K+nu are the most studied channels in SuperK, and in HyperK in the upcoming future, with more statistics, it's estimated a 3sigma signal significance in 10years HK run. SK ruled out a lot of GUT models, and there still some SUSY GUTs within the sensitivity range of SK, and Hk, a lot of things will come.
Thanks for the info! Althought I'm pretty certain how this is (not) going to turn out and 3 Sigma is... well, 3 Sigma, it seens like pretty cool research.
U speak weird
99.7% of all results should fall within +/- 3 Sigma. Anything outside of that range has a .3% of occurring randomly and may not violate any theories or models. This is why it's important that science tends to go for the 6 sigma with only 3.4 events out of a million that it was a fluke, which for the most part probably means your result implies that your hypothesis (current working theory) needs reworking.
To put that into perspective, 3 sigma has 66,807 "flukes" per million. Not a lot, but it's enough to worry people that your data may not actually be outside of current theory. You can see why 6 is the gold standard.
@@frankn254 I Agree.
SO(10) GUT? 🤔
Question: What are these "new theories" and how do they improve the standard model ("best theory ever devised"), respectively, what are the gaps in / the shortcomings of the standard model?
There are many new theories. Tons of them. What they are trying to solve is the nature of dark matter and energy. They are trying to understand why there are quarks and leptons. They are trying to understand why there appear to be a finite number of forces (different people, counting different ways, come up with numbers in the range of 4 - 6 or so). They try to bring gravity into the picture, which is currently not true. They try to understand the nature of matter and energy shortly after the Big Bang.
In short, they try to extend our understanding of the laws of nature. We don't understand them all. We've made great progress in the last century, but there is a lot of the way to go.
Sabine’s point (that I happen to agree with) is that these “new theories” aren’t theories at all, because they aren’t a response to observation, but instead are an attempt to create a “more mathematically beautiful” theory than the SM. The reason is that an hypothesis is a response to an observation, and that in explaining the observation it can make predictions about things not yet observed. Think about how GR explained the orbit of Mercury, and the same equations also predicted that light would bend around a gravitational field, which was confirmed during the 1919 Total Solar Eclipse. Various “New Physics” theories aren’t explaining observations that the SM can’t, because SM works great. Rather they are trying to guess what we’ll observe at higher energy levels (or longer timescales) than we can currently generate. This is backwards from the way science usually works. What’s great about this is that when their predictions fail, the theorists can generate another theory and claim that they’re doing science because they moved on when their ideas were falsified.
Current results at LHC aren’t too promising for new physics, either. To date, nothing has been unequivocally observed that isn’t handled by SM.
But the quest for proton decay will provide grant proposals and publications for a few more years, at least, so there’s that.
@@drdon5205 Thanks for that rather elaborate reply!
@@TheGotoGeek You are mischaracterizing the history. General Relativity was devised as a theory on aesthetic grounds. Only later did it answer the problem of the precession of the orbit of Mercury. In fact, Einstein first miscalculated this problem and only fixed it later. The theory was most certainly not devised to solve this issue.
And, on the SM, again I would disagree. The SM does a great job on many things, but there are many questions it doesn't answer. These new theories are all attempts to extend the SM, not on aesthetic grounds, but because those questions need answers.
It is true that some theorists use aesthetics to guide their thinking, but what would you have them do? Consult tarot cards? The goal is admirable and you have to try >>something.
GR isn't an aesthetic argument, it resolves an inconsistency. A falling object appears to be accelerating but a falling accelerometer reads zero.
It's a blessing that theoretical physicists are able to witness their theories unfold within their lifetimes.
The standard model isn't just flat out wrong (the observable universe didn't match the predicted model so they invented unfalsifiable dark matter to rectify. Unscientific!) but it is DESIGNED to be wrong. Human physics was subverted 100 years ago and the why was likely to stop us reaching the stars as a species.
If youre a budding physicist. Go back and study pre 1927 classical physics and disregard modern falsehoods like the SM.
This was cutting edge research back in the early 1980s when I was a physics student at the University of Michigan. I think it was Professor Tris Coffin who brought our honors class on a tour of Fermilab in 1983 or 1984. I'm a bit glad they haven't seen any proton decays, but am a bit bewildered by the tweakings of theories. Good you got a new detector for your neutrino line, I remember the 15' deuterium bubble chamber well.
In another 40 years they'll have an even bigger detector, a more tweaked theory, and still no evidence of proton decay.
When you say you're a bit bewildered by the tweakings of theories, do you mean you think it would make more sense to conclude that those theories have been experimentally ruled out? Or is it the ways that people have tried to tweak them that doesn't make sense to you?
IMB experiment⁉
Fascinating! I do wonder, though, what role the Baryon Number conservation plays in the Standard Model? It just seems arbitrary, like it was devised to "rule out" things that we don't see, but that there isn't really any other good reason to rule out the possibility. If we know that baryons are made of quarks, and we can account for all of those quarks (as you suggested), why is that not a good theory? Have we tried to destroy protons and found that we couldn't? Otherwise, baryon conservation seems like one of those things thought of when protons were thought to be elementary.
interested in this as well. a lot of the 'rules' sound like an awful lot of arbitration, but that just might be the way they name them tbh
My basic understanding comes down to this:
Conservation laws are the results of symmetries, as we all know from the very famous Noether's theorem.
The theory of strong interactions and it's gauge symmetries are QCD, and QCD of course describes the behavior of quarks and gluons. The equations of QCD are invariant under a global gauge transformation, which gives rise to a conserved quantity.
These conserved quantities are simply added degrees of freedom that we assign a name to because we know it is an intrinsic property that is conserved. We assign these names like charm or strangeness or baryon number.
In the case of charm and strangeness, these values are conserved in strong interactions (nuclear) but not weak interactions (decay).
All of these conserved quantities just give rise to more degrees of freedom, which we call quantum numbers. Other examples of such quantum numbers are mass, electric charge, lepton number, spin, isospin, hypercharge, flavor, parity, helicity, color charge, principle quantum number, magnetic quantum number, total angular momentum, etc etc. Many of these can be broken down into further subcategories.
If you ask me, it's a bit confusing and out of hand, but when you take them in one by one they all seem decently well justified. However, I've only got a basic understanding of such things. I am not a nuclear nor particle physicist, just a hobbyist. I hope this helps though.
It is worth noting that QCD in particular is quite tricky. The strong force has such a large magnitude that non-perturbative effects may have a major impact on it, so there are many theories that depend on these effects. I've heard of chiral symmetry breaking but unfortunately my knowledge of QCD is pretty limited and I don't understand this enough to explain it. For some more information about this type of thing, look into sphaleron processes. These come from electroweak interactions which have been shown to violate other conserved nuclear quantities, as stated above. Pretty interesting stuff!
When it comes to quarks, there are 2 types of particles. Baryons (which have an odd number of quarks), and Mesons (which have an even number of quarks)
(This means that, in general, the Baryon Number of a Baryon is actually [#Quarks - #Antiquarks]/3. So if you had a pentaquark composed of 5 quarks, the baryon number would be 5/3. But for any Meson, which has an even number of quarks, this number is defined to be zero. However, particles with 4-5 or more quarks are exotic particles with extremely short half-lives, so they only show up in particle accelerators. Same thing with single quarks, which we don’t see in nature due to a phenomenon known as color confinement, which arises because of how strong the Strong Force is on small scales. Thus we typically talk about particles containing 2-3 quarks in most scenarios)
Anyway, each quark has a spin of +/- 1/2, which leads to why the numerical parity of quarks (even/odd) matters. With an odd number of quarks, you get a half-integer spin (1/2, 3/2, etc…), whereas with an even number of quarks, you get integer spin (0, 1, 2, etc.)
As it turns out, this has a huge effect on the way particles behave. You might be familiar with something called the Pauli Exclusion Principle from Chemistry class, which decides how electrons fill the electron orbitals of an atom - each electron takes up a different slot among the possible electron states for that atom. This is precisely because electrons have half-integer spin (they are not composed of quarks, but every fundamental particle will have either integer spin or half-integer spin)
Particles with half-integer spin are called Fermions, and follow something called Fermi-Dirac statistics. This is basically a generalization of Pauli’s principle, and it says that 2 Fermions in the same system cannot have the same set of quantum numbers (e.g. with electrons, we have n = 1, 2, 3, …; L = orbital shape = 0, 1, 2, …; m_L = orbital orientation = 0, +/-1, +/-2, …, +/-L; and m_s = spin = +/- 1/2). This tendency for Fermions to “spread out” among all possible quantum states has a huge effect on their observed behavior
On the other hand, particles with integer spins are called Bosons. Most of the time we tend to talk about the fundamental Bosons, which are not composed of smaller particles. These are exactly the force-carrying particles in the Standard Model (Photons for Electromagnetism, Gluons for the Strong Force, W and Z Bosons for the Weak Force, and yes… the Higgs Boson, which is how the fundamental particles obtain mass - but it’s not actually a “graviton” for the Gravitational Force, which is outside the standard model)
Anyway, we can also talk about composite Bosons as well - anything with an even number of quarks (Meson) will also be a Boson. Ultimately, Bosons follow a completely different set of behavior known as Bose-Einstein statistics. The basic idea is that you can have as many Bosons as you want in the same quantum state, and they are perfectly happy. For instance, this is what allows LASERs (Light Amplification by Stimulated Emission of Radiation - in this case, “radiation” refers to Gamma Radiation, aka Photons) to work. Lasers emit a beam of photons that all have the same exact amount of energy (and therefore the same wavelength), so you obtain an extremely coherent beam of light that is all a single color (unlike a lightbulb in your house, which will actually emit a range of wavelengths across the visible spectrum, but our eyes only see the average color, such as white/yellow/etc. depending on how the bulb is designed)
(I believe LASERs operate by what one might call reverse-spectroscopy. Basically, find an atom/molecule that emits a spectral line of the wavelength you want - which occurs via an electron level transition that emits a photon of the required quantum energy - then find a way to make that specific transition happen consistently and repeatedly within a macroscopic amount of that substance)
So that’s it. Baryons are Fermions (odd quarks = half-integer spin), whereas Mesons are Bosons (even quarks = integer spin). This gives us some idea at an “intuition” level as to why Baryon Number might be conserved
(However, arbitrary Fermions and Bosons are not necessarily conserved. Though it seems like this happens when 2 or more Fermions create a composite Boson - 1/2 + 1/2 = 1 - which would not happen with a possible Proton decay into a smaller particle, for example)
@@Muhahahahaz But was is there to stop let's say... a Proton and a Neutron to change into 3 pions? we have 3 up and 3 down quarks in each system and the second system has less mass.... But the baryon number (which is not a property of fundamental particles) isn't the same....
I also find it fascinating that the standard model predicted the existence of the Higgs Boson to explain how particles obtain mass but as far as I know the other properties of fundamental particles (spin and charge?) are not explained through other particles.
@@Muhahahahaz Technically, a pentaquark would consist of four quarks and one anti-quark; so the baryon number is still 1. With five quarks it wouldn't have been possible for the particle to be color-neutral.
I am a big fan of Dr. Don. Watched his presentation style improve gradually over the years, I admire the persistence and of course the informative videos.
For people asking about Sabine's video, here's the reason why people want extensions of the Standard Model:
1) The SM can't explain the imbalance of matter vs antimatter, why there seems to be exactly 3 generations of particles, as well as stuff like the mass of neutrinos.
2) The SM is known to fail, albeit at scales far, _far_ greater than anything we've been able to probe. It's _possible_ we won't find anything until we get a collider the size of Jupiter but we don't know that for sure.
3) The SM has no underlying explanation of _why_ it is the way it is. It's just a bunch of facts about the universe that have no underlying explanation. That's never been good enough, and every time we've ever gone "that's it that's all there is to it we know how the universe works now" we've been wrong.
4) Even if it's not about breaking the SM, isn't it good and worthwhile to refine it, figure out exactly what experimental parameters we need? More precision in fundamental knowledge is always good in and of itself.
The day has only 24 hours and at some point we need to stop and ask where we should be better be spending our research time and money. Do we just keep on building bigger tanks of water?
@@spaceman4286 The one thing we don't know much about is neutrinos. And Fermilab is not a tank of water. And the other experiments were not designed to specifically look for proton decay.
And for neutrinos, yes we are probably going to keep building bigger tanks of 'whatever' because they are the biggest unknown right now.
I don't know about the rest, but concerning point 3) she talked about it. Basically, there is no need to ask for why things are, some things just are and there is no way to really "explain" it, like constants of nature. Knowing why things are the way they are is only useful if it helps make predictions, as long as we can predict with perfect accuracy what a blackbox is doing we don't really need to invest the huge amounts of work and ressources figuring out how that blackbox internally works, if such an explaination even exist. I'm not a physicists, but it really seems like particle physicists are sort of just randomly making theories and then try figuring out how to create the observations that require their theories.
@@JohnDoe-jp4em the vast VAST majority of times people in history have said "some things just are and there is no explaining _why_ they are", 100 years later someone had found the explanation as to why they are. "Oh why do chemicals react the way they do? Idk, they just are! We can describe the patterns pretty well, though, so that's good enough" until oh hey there are these things called electrons and they explain how chemicals interact.
Until we figure out all of it, yes _all_ of it, it's worth keeping investigating. And that's a pursuit that will never end, because that's what science is about. Pursuing knowledge and answers.
As for "sort of just randomly making theories", they aren't randomly making them, they are looking at existing patterns and asking themselves why this part of physics follows different patterns than this other kind of physics, and asking mathematicians "hey do these patterns ring a bell? Is there any logical relationship between pattern X and pattern Y?" And when mathematicians go "oh actually there is! They're both aspects of a bigger pattern, XYZ", physicists go "okay that's certainly a possibility worth exploring!" and they look for pattern Z and then don't find it, and go "hmm, okay, that was wrong, strange how we get X and Y in the universe but not Z, I wonder why" and so on. That's worked for physicists before, and it's actually exactly how the quark model was discovered, and honestly it's the best way we know of to come up with deeper explanations.
@@ericvilas Without knowing that electrons and orbitals exist you would have an extremely hard time predicting chemical reactions. The only way you could predict something would be to record what happened and did the exact same thing again.
Yeah it would be cool if we knew absolutely everything but that's both not possible and an extremely wasteful goal to pursue. It's not worthwile to dumb billions of dollars into experiments that are a shot in the dark whether they will even turn up anything useful or just "guess we need to look harder". Prioritization needs to happen, there is a finite amount of money and workforces available and it's not smart to use a large chunk of it to try to randomly guess theories that are not even required to explain an existing observation.
It seems kinda true that particle physics is not really productive when despite access to the most expensive toys in science there are no new major advances in 11 years.
Thank you for a presentation that acknowledges things are much more complicated, while sticking to the relevant bits. It's a great jumping-off point for digging deeper into these issues for laymen like me.
Thanks to Dr. Don and Fermilab for doing serious research.
Except this video is wrong, his first statement is incorrect, and he should know better.
@@annaclarafenyo8185 Which statement? 🤔
@@annaclarafenyo8185 Are you referring to the 1H segment before the intro? When someone says "You know, hydrogen is all around the Universe since forever!" you don't automatically question "define all H isotopes, all around and Universe". C'mon, even chatbots from 1997 were smarter than this...
"Serius" research? No thanks to the quality of education in your country.
@@johngrey5806 God forbid someone not being an English native! Aliás, aposto que meu latim enferrujado que aprendi há 30 anos é melhor que seu inglês nativo.
This is all so fascinating. I’m so glad that Fermi labs is sharing this information to the rest of us.
So amazing. Until you mentioned it, I never thought about how long atoms lived, considering the current law of conservation of energy. Great topic, and thank you.
Another Tremendous production from my FAVORITE high-energy physicist!!
I'm more concerned with my own decay I must admit..
How about a discussion on what CAUSES stable particles to decay??? We know the proton's charge relationship with the background scalar field pressure CAN be modified by use of high-intensity canceling MD & EM fields surround the proton to be affected; hence affecting it's self-stability. This mechanism operates by modifying the local refractive index of the vacuum within the interfering wave cross-section, and has tremendous implications far beyond the scope of this video!
I have to say it's pretty funny watching this video after Sabine Hossenfelder's latest one.
All I could think about, frankly.
I am not sure funny defines it but yeah, it was something.
There are as many opinions on the subject as there are physicists. She's just one of them, and she's not always right.
She speaks truth. After Einstein years nothing much is achieved in Physics.
All the work is derivative of work done by Einstein and other greats like Schrodinger, Dirac etc.
yep
Baryons do not "consist of 3 quarks". These are the valence quarks, but there are also sea quarks and gluons. Moreover the Standard Model does allow for baryon number violation, only the difference between baryon number and lepton number is strictly conserved, as a global symmetry. However, the SM proton decay is extremely slow, and therefore not observed.
I'm sure he just simplified the description in the video because that wasn't the main point (and the 3-quark model is pretty much any physicist's first-approximation to describing a proton), but I would love it if he made a video discussing the quark/gluon sea inside of protons and neutrons. PBS spacetime recently made a video discussing this in some detail.
You're a great host. :)
Again, best science channel. I never miss new videos from Dr Lincoln. Thank you!
Has an anti-neutron ever been observed decaying into an anti-proton, positron, and electron neutrino? I'm not saying an anti-neutron would decay differently, just that I know these kinds of interactions are desirable to observe in antimatter
I reckon that such a reaction would be difficult to observe. Because I don't really have a box of anti-neutrons in my backyard. How do you make anti-neutrons anyway? In high-energy nuclear reactions. It follows that the resulting particles will usually propagate at a speed close to the speed of light. Plus, how do you control the movement of particles? With electromagnetic fields. But there's a difficulty that anti-neutrons are electrically neutral (though neutrons - and it follows that also anti-neutrons - are known to have magnetic properties due to being composed of quarks). Finally, what's the average lifetime of a free neutron? Almost 15 minutes (that's nearly an eternity in particle physics). So good luck holding an anti-neutron for a period of a number of minutes without it annihilating with ordinary matter.
Wait, isn't a neutron it's own antiparticle???
@@xochitlpauli5622 It's not. Protons and neutrons consist of quarks; antiprotons and antineutrons consist of antiquarks. (There do exist baryons [as opposed to antibaryons] with charge -1, but they consist of three quarks with charge -1/3 and are unstable. There also exist unstable baryons with charge +2, consisting of three quarks with charge 2/3.)
Yes
@@rodocar2736 Do you have a link to a paper about this observation? Because I tried to search for it, but only found searches for neutron-antineutron oscillations.
Hey Doc Don! I'd love to see a retort to Sabine Hossenfelder's video expressing her frustration with Particle Physics and Particle Physicists. You seem like the perfect person to refute her claims. Either way, it would be great to hear from both sides.
Well, there's actually nothing to refute in her claims. They're not saying anything in conflict with each other. Standard model predicts, that protons do not decay. And this is actually what we are observing. But there are physicists who don't like some properties of the standard model, so they're trying to create new theories that address those properties of standard model that they don't like. These new theories make predictions such as the fact that protons do decay. This much is said even in this video, even in videos by Sabine Hossenfelder.
The only difference is, if this experiment doesn't find the proton decay, these guys will just apply for funding of building an even larger experiment, because the current experiment can only find proton decay if it happens after certain long value, but this experiment (and in fact no experiment) will not rule out the chance that proton decay occurs but it's even more rare. This is called a black swan problem. No matter how many white swans you have seen without ever observing even a one black swan, you can't rule out the existence of a black swan and say all swans are white.
Same way, particle physicists cannot rule out, that proton decay might be occurring in ranges they have not yet experimented with. They can only rule out that it occurs in the ranges that they have experimented with.
And this is what they could keep doing very hypothetically infinitely long. We didn't detect anything in this range? Doesn't matter, let's look for it at even larger scale.
Sabine thinks, this is waste of money and you're not going to find new science this way, because if Standard Model is right and there's really no proton decay, then it doesn't matter how large of an experiment you build, you will never detect any proton decay.
So now we have to come back to the question, if standard model doesn't predict proton decay, why do physicists even try to look for it? Because they want to see if their theories, that are addressing some things they don't like about standard model, are correct. But is there actually any good reason to invest money into these new theories?
Sabine argues, that no, because these new theories are not really necessary to explain any observation that we have made so far. There are things that the standard model actually can't explain very well, but most physicists are not even trying to address those problems, they instead focus on what kind of numbers they have to plug into equations so that the models make good predictions. In case of standard model, they have to put numbers, that have precision of many decimal places and it's not a simple 1 or a 0. So they are creating mathematical models, where there would be nice round values, which looks better on the paper, but actually doesn't describe any currently observed and unexplained phenomenon. So it's a waste of time and money, argues Sabine.
These guys argue, that well, they're looking for something and if they find it, it would be a great shift if physics and if not, no harm done. They don't necessarily agree, that money or time should be the limiting factor on what science experiments will be carried out. We should ideally do all experiments possible, they would probably argue. But of course we have finite resources, so....
But imagine you're a particle physicist and your livelihood depends on being able to perform some experiments, but you have no idea what kind of experiments to perform, because standard model is already covered by experiments and there's no low hanging fruit within the realm of properly addressing issues in the standard model, so it would be hard to get funding for that. You see how these physicists are motivated to keep working on easier problems that will get money.
That would be a great idea, Sabine is incredibly brave to poke the Big Physics bear and Don is someone who could sympathetically argue the inside view in a way that would be comprehensible to the rest of us. These two presenters are giants of making Physics accessible.
Thanks Dr. Don.
Colgate is out with new paste to prevent Proton decay. Use Colgate Protonium and save your proton from decay for 10^31 years.
Yes, I hear it is even approved by the ADA - The Awesome Don Association.
Love these videos!!
I Absolutely Love the Intro Music, it's the Best, my Favorite
Hi Dr. Lincoln!
I wish you had talked about the specific ways conservation laws might be relaxed in theories beyond the Standard Model. For example, protons might decay into specific particles because while baryon number isn't conserved, certain _combinations_ of baryon number and lepton number are conserved, and that's what would need to happen for the decay to happen.
Baryon number is not conserved even in the standard model, it is violated non-perturbatively by an SU(2) Instanton. This process is impossible to practically observe, but it does happen eventually. Only B-L (Baryon minus Lepton number) is preserved in the SM.
Santa Lincoln is back! 👍
"they made a prediction about this alternative theory. It did not succeed, so we need a bigger test setup". Sabine is fuming right now! She may even decay ;-)
Except in this case, Fermilab constructed the "bigger" test setup for a completely different purpose, and is piggybacking the proton decay experiment on to of it. Assuming she approves of the main use of the equipment, this is the type of thing she'd probably approve of.
I would like to see Sabine debating her problem with "big science" with someone who disagrees with her, not least because I want to hear what she says we should be doing instead.
@@EnglishMike Yeah, I'm glad DUNE had other purposes and that proton decay _might_ be a side effect they can look for. As far as Sabine is concerned, I treat her like Neal deGrasse Tyson and respect their expertise in their own fields but when they talk about something outside of that I look for experts in the field they are discussing for verification.
One of your best prestations.
Cannot get too much of Don's lectures ------ so excellent
Could you observe other types of baryons to determine if they ever decay into a manner which doesn't conserve baryon number. Other baryons decay very rapidly so they would be a large number of decays rather than waiting on proton decay. The failure to observe a violation of baryon conservation would give strong evidence (although not 100% proof) of proton stability.
You can. We do. And they don't. Baryon number is 100%conserved in all observed decays.
I believe that is actually the original reason for its introduction. It was observed to be conserved. Though now, as far as I understand, it is based on some symmetry of the model.
How do these alternative theories propose baryon number could be violated?
The conservation of baryon number is only approximate. That is, there are situations in which it does not hold. It does not arise from an underlying symmetry following Noether's theorem.
@@michaelsommers2356 The baryon number conservation symmetry is U(1)_V (see www.damtp.cam.ac.uk/user/tong/gaugetheory/gt.pdf, page 244).
@@drdon5205 That's not what I have read elsewhere, such as
www.slac.stanford.edu/econf/C1307292/docs/IntensityFrontier/BaryonNo-13.pdf
@@michaelsommers2356 An excellent reference, but the first pages say lots of "If baryon number is an approximate symmetry," suggesting that there is some question.
In addition, a (very, very) quick perusal of the paper suggests that it is pointing out that the symmetry could be broken in different theories. In short, isn't the paper trying to motivate extensions of the SM in which baryon conservation is broken?
If so, then we'd see baryon number violating decays, which we don't. That said, we do look, essentially to find out if the "If" of this paper is real. This was kind of the point of the video.
One thing on which I am sure we would agree is that theorists are clever and can often develop theories which violate symmetries that are incorporated in existing theory. Finding those violations is an excellent way to find clues about new physics.
Because Grand Unified Theories imply that leptons and quarks are connected, meaning that the only true conserved quantity has to be the difference between lepton and baryon number (B-L).
- neutral +
Charges cancel each other Electrons (-) Protons (+) Neutrons Neutral
Transfer of charge
As above so below... This applies to so many levels
so what about reverse beta decay/electron capture?
That requires additional energy.
This is an excellent example of why science is the gift that keeps on giving. Assuming one sees new fascinating questions as a gift. Proton + electron + energy to smash them together = neutron. Makes sense total sense; a neutral particle made by the combination of + and - charges and slightly heavier than a proton because it also includes an electron. Neutron decay = proton, electron, released energy *and an anti-neutrino?* New gifts: Where the hell did that come from? Does the decay create antimatter or was the antimatter created in the fusion of protons/electrons?
Q:
Is there any predictions that the standard model predicts that are inconsistent with experimental data? Or does it make predicitons that cannot be correct (ie prediction would break other known laws)
If the answer to both is none why are people trying to 'reinvent' the standard model?
I'm just confused why anyone would suggest alternatives to a model that has not been proven to have inconsistencies/make predictions not fitting the known data.
They look for a better model because, even if the current model contains no inconsistencies, it doesn't explain everything. It says nothing about quantum gravity, for instance. It doesn't say what dark matter is.
It's a model. That's the simple answer. It's a simplification of what we can observe. As long as we don't know the full extent to which every known phenomena works we can't be sure of anything. In the same way Newton's theories work, they break down at a certain point.
It's a philosophical question. Sabine Hossenfelder is an instrumentalist; I guess most particle phycisists are realists.
Sabine's take in what Particle Physicists do nowadays is to me the most concise and close to the truth. The field has gotten so big that now it feeds itself, and different thinking is not encouraged:
ruclips.net/video/lu4mH3Hmw2o/видео.html
@@michaelsommers2356 We saw that in large scale GR doesn't work and we assumed that is because we are missing matter but we shouldn't rule out GR is wrong too.
DUNE experiment?!
The spice MUST FLOW!
Question for anyone:
Given the theoretically-predicted 10^31 yrs lifespan of the proton...
What size would a detector monitoring vacuum space have to be, in order to expect to find a single instance of proton decay within a ten year span?
Thank for commenting.
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Big.
Why would you want to monitor vacuum? Wouldn't monitoring somewhere with actual protons be more productive?
You need a medium for the decay products to interact with to detect a result. I’m guessing the because of Argon’s atomic density it’s a “bigger” target chance for a decay product to run into and interact with.
Best channel. Love watching your videos!
"If detecting proton decay were easy, everyone would be doing it. Or no one."
Can you explain where baryon number comes from? At the surface it seems pretty arbitrary to say that proton and neutron are +1, their antiparticles are -1 and everything else is 0. Where does it come from, and, most importantly, why should it be conserved?
The conservation is due to "U(1)v global symmetry of the QCD Lagrangian". Not helpful I know, but the standard model is described by math and the conservation laws are consequences of the mathematics. Think of an interaction as equations with the original particles on the left, and the resulting particles on the right. On the left hand side you have a certain number of equations describing the quarks inside a baryon, and on the right hand side you need another 3 matching equations to describe the resulting baryons after the interaction.
A new model, usually called GUTs (Grand Unified Theories), could have different symmetries that change those equations so that one of the baryons is converted into a lepton (eg. the positron) so that the right hand side of the equation only needs 2 equations to describe the baryons, although I know nothing about the GUT theories so I don't know the exact mechanism of the equations.
“Baryon # conservation” is really is really just a consequence of “quark # conservation”.
Basically, no known physics exists that can transmute a quark into a lepton, or vice versa. And “baryons” are just combos of multiple quarks, so any reaction or event that starts with N quarks must end with N quarks. However, matter-antimatter pairs of quarks and leptons can be created from pure energy or annihilate back to energy, so to handle those cases “N” is really (#matter quarks) - (#antimatter quarks). That’s why the math to model this underlying conservation law assigns +1 for matter quarks and -1 for antimatter ones, which turns the pairs into 0s.
“Lepton #” and “lepton # conservation” are literally the exact same thing, only for leptons like neutrinos and electrons rather than quarks. And all of it arises from one simple, mysterious observational fact: Matter seems to come in 2 types, “quarks” and “leptons”, and we’ve yet to observe any force capable of turning a quark into an electron or vice versa.
AFAIK there is no known deeper principle. It’s not like conservation of energy or momentum, where physics obeying symmetries in space and time leads directly (mathematically) to the resulting conservation law in any equations modeling it. These #s are conserved simply because no known particle interaction breaks them, and therefore the Standard Model’s equations (which model such interactions) always conserve them. That’s one reason new physics that “broke” lepton and quark # conservation would be way less shocking than, say, a violation of momentum conservation.
Thanks to Dr. Don, Your explanation is always on next level, simple yet perfect
I was wondering if you could let me know how to calculate the mixing angle and construction of PMNS matrix
So, what would then happen to the daughter pion? As I understand it, pions are exchanged by nucleons as strong nuclear force interactions. Since this is an extremely short-ranged force, wouldn't pions be unstable outside the nucleus?
A neutral pion is made of a quark and the corresponding anti-quark. They mostly annihilate into photons.
@@narfwhals7843 So what happens to the baryon number it carries? I understood that conservation of the proton's baryon number is why the meson is needed in the interaction.
@@byronwatkins2565 this process would violate baryon number conservation.
Things physicists say: "The previous theory stated that the half life was like 20 orders of magnitudes longer than the age of the universe, but it seems that it doesn't decay that QUICKLY after all..."
Thank for commenting.
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Nothing like spending money to see if a particle decays that has a longer life than the universe so it can't even affect us anyways...
It can, improving the knowledge on particle physics is crucial for better understanding of how matter works, and discovering new ways of using it properties. (We can see it clearly on how our understanding on quantum electrodynamics improved chemistry and semicondutor/computer sciences). Science isn't a waste, it's an investment.
Thank you very much. In p^+ --> K^+ (u sbar) + nu, is the nu (neutrino) actually a nubar (antineutrino), so you are looking for conservation of B - L? Which (anti)neutrino flavor(s) are you looking for?
Any updates on the data of 2nd or subsequent runs of g-2 experiment?
Not any I can find.
It's expected to come out "soon," where soon is kind of unspecified.
So if decay products have to conserve the baryon number and since protons are the lightest Baryon...
When you smash 2 protons together there still has to be 2 protons in the debris, that says to me that all other particles are created from the energy of the collision.
Unless there is a baryon lighter than a proton that we haven't ever seen yet.
Also can protons be annihilated (without an antiproton collison, we know antiprotons have -1 baryon number so the baryon count is zero after such a collision) and what happens to their baryon number if they can be annihilated by any other means`?
A collision is not a decay. There is additional energy. So the debris can include _heavier_ baryons, like neutrons.
What would a annihilate a proton if not an antiproton?
@@narfwhals7843 Any collision with enough energy to overcome the strong nuclear force theoretically could annihilate a proton.
But there is still a lot we don't know, like what happens if the strong force is overcome. Quarks theoretically can't exist alone so would they decay or would the proton reform from the free quarks?
Or would that much energy create some exotic superheavy particles or change the flavor of the quarks?
Don, we are told that protons are made of two Up and one Down quark. The neutron is made of two Down and one Up quark. Also, we are told that a neutron star is formed when electrons are forced into the nucleus and convert the protons into neutrons. How can an electron change an Up quark into a Down quark, and why does an electron not affect the neutrons? Also, we are told that heavy elements are formed from the debris when two neutron stars collide. How are protons formed from the neutrons, and in the exact number needed to form each heavy element?
Up quark has a charge of +2/3. Down quark has a charge of -1/3. The W boson has a plus or minus charge. In the case of neutron decay, d (-1/3) -> u(+2/3) + W(-1). The W then decays into and electron and antimatter electron neutrino.
The opposite can be true, too. Shove an electron into an up quark and it can become a down quark. That takes energy, which is given by gravity as it squeezes the star.
these questions don't have simple answers. This might partially answer one or two of your questions: ruclips.net/video/u05VK0pSc7I/видео.html
@@drdon5205 What happens to the charge of the electron?
@@MusicalRaichu I started to read it, and quickly found more questions. A google search for answers produced more questions. I think it will take the rest of my life to understand the answers to my questions, but I'm afraid I may not live that long.
Since electrons have mass their movement can be restricted by gravity, something a neutron star has so much of that it can overcome Electron Degenerate Pressure (electrons not wanting to be in the same place at once) This means multiple electrons can exist in the same place at the same time inside a neutron star. The electrons are still 'there' however they are no longer individually taking up any volume as they do in normal matter. The space a neutron star takes up is just the volume of protons but their charge is being canceled out by a cloud of super positioned electrons.
In all honesty it is better to think of a neutron as an exotic atom between a proton and a electron in essentially all scenarios. Quark theory is great and all but its more math than actual physics 🙃
0:00: 🔬 The stability of protons and electrons is important for understanding the laws of nature and the future evolution of the universe.
2:37: 🔬 Einstein's equation relates energy and mass, while baryon number represents the number of quarks in a particle.
5:25: 🔬 The proton is the lightest baryon and any proton decay would have to conserve electric charge, energy, and baryon number.
8:00: ⏳ The predicted lifetime of a proton is much longer than the age of the universe, but some protons will decay early due to statistical processes.
10:44: 🔬 The DUNE experiment is looking for proton decay and has a high sensitivity to positively charged mesons and neutrinos.
Recap by Tammy AI
I like that fermilab designs experiments to look for many things at once, that looks to me more promising than many other experiments.
I suppose its partly a tradeoff certainty-of-find vs chance-of-finding.
@@-dennis3755 yeah. I guess.
I still feel like we could and should do better in deciding what experiments to do and which not to do. But Fermilab looks overall promising to me. Let's see.
The likelihood is that it won't find anything. It will only cost a lot of money.
Very clear explanation
Great stuff! As usual. Thank you, Fermi lab!
Thankyou.
Some issues to consider; protons only make a tiny proportion of the universe's energy, perhaps just 2%.
What protons do exist are being continually crushed out of existence in vast numbers in black holes and neutron stars.
While they may not decay quickly, overall, the outlook for proton durability doesn't look very good.
Would a proton being bound into a complex nucleus (eg. Argon) be more or less likely to decay, I wonder?
yes! that's called beta plus decay, it happens all the time
Neutrons are stable in a nucleus but unstable by themselves, so in principle it could have a big influence
@@neut9270 Yes and no. It happens in some nuclei, but not all, so far as we've seen. Would it happen in Iron-56, for example?
This confused me too. In PET scanning (positron emission tomography), the positrons come from protons in a radioisotope nucleus emitting a positron (and a neutrino) and turning into a neutron. This is beta+ decay.
It was otherwise a great video, but how this situation is different should have been addressed.
@@stevendzik7312 I think they are talking about proton decay wih no external energy input. Beta+ decay requires energy input as the results have more mass.
Good explanation.
Given our recent reassessment of certain physics methodologies, this video is quite informative.
Had me confused for a minute since beta+ decay is a thing (proton decays to a neutron and steps down 1 on the periodic table), but then I caught on to the fact you were talking about isolated protons. For anyone else who might have missed that bit, beta+ decay only happens in a nucleus not in a lonely proton, conservations are maintained.
Essentially it would have to decay into something that's not a baryon. I don't believe it happens.
Yet again, a succinct, but entertaining video from the good Doctor. Thanks Fermilab, this channel is excellent!
What would they decay into?
Super Kamiokande looks like a perfect venue for a live Squarepusher show
Very very good! You see, this is why also the Photon has mass!
Would love a segment on your response to Sabine H.‘s recent video.
Did Sabine criticize experiments that attempt to falsify the Standard Model? I thought she criticizes theoretical physicists whose theories are either (1) unfalsifiable or (2) uglified after earlier, more elegant versions were falsified.
@@brothermine2292 ruclips.net/video/lu4mH3Hmw2o/видео.html
@@brothermine2292 She also talked about things like that I dont remember for sure but maybe exactly on the proton decay problem too. They just move the time it takes for a proton to decay longer and longer in those theories.
@@brothermine2292 She criticized that particle physicists create theories, then create experiments afterwards to create the observations that require that theory. And if the observations don't happen, the theory gets adjusted to require an even larger experiment to falsify. In that way those theories aren't really falsifiable, because scientists spend their time crafting theories that are always outside of the capabilities for falsification. Theories that might be true, but don't predict anything better than other theories and are too expensive and time consuming to falsify are kinda worthless, because you can create an infinite amount of theories like that which are all equally valid.
New question. Since protons are big bang energy condensed, can we reverse the process and get all proton energy?
Whats the problem to achieve this energy?
i've never heard it explained this way, or this clearly before. Thanks.
What about if the Proton's decay scheme is similar to a Neutron's decay scheme, ie, a neutron when it is not bound into a nucleus has a half life of 12 minutes (when bound, it's relatively stable -- ie, you have a stable nucleus, not an isotope that will decay), what if the proton is the same? While bound in a nucleus the proton is stable, but only when not bound in a nucleus, it can then decay.
An interesting idea, but since most Hydrogen is just a proton in the nucleus and its ionization energy is low enough for us to be able to get rid of its electron fairly easily, you'd think someone would have noticed if something happened.
Missed you Don!
Newb question? Do single protons of different elements differ in any way? Ty!
No, the protons in hydrogen and chlorine and gold are exactly the same.
@@kitmoore9969 ty. I had wondered about that on the quantum level.
Am I the only one who, whenever he hears about “conservation of energy”, instantly pictures Nick Lucid’s “conservation of energy shall not be violated!!!” Meme?😂
Not at all - gets me everytime!
He is very funny.
And can you please explain the concept of point masses like electron's physical size and also how long or small a photon is? I mean we say its stretched by redshift or space expansion incase of cmbr and we say photons are quantized so they must have finite dimensions?
Quantization is a commonly misunderstood concept. (Quantum Physics is one of the many, many, maybe even majority of things in science that is very poorly named.)
To the best of our ability to tell, the universe _is_ analog, not quantized. Certain things are quantized, not because the nature of reality is somehow digital or quantum, but because certain things in very specific situations are.
For example, a free electron can have any kinetic energy, no quantization needed. An electron _bound in a hydrogen atom_ on the other hand, can only have certain very specific, quantized energy states.
It's loosely analogous to a guitar string. Free, on its own, the string can move however it wants. _Mounted on a guitar_ on the other hand, it is constrained at both ends, and can therefore only vibrate at the frequencies dictated by those constraints-by the tuning tension and the current fret it's being held against.
Since light is created by the change in energy state of charged particles (mostly electrons), and electrons are mostly bound in atoms (it's a very specific state, but an overwhelmingly common one, heh), it's very _common_ for a given photon to have an energy/wavelength of very specific values... but it's not _necessary._
If you want to know more, especially about the sizes of particles, I'd highly recommend Dr. Sean Carroll's "Big Ideas" series. It's basically a crash course in the whole of what's firmly "known" in fundamental physics that he made during lockdown, covering basically everything we know about how the universe works at a level somewhere in between normal layperson pop-sci communication, and what you'd learn studying it in university. It includes this topic, but I don't know that I'd recommend just watching that one episode, as there's a lot of context you might be missing.
_Unfortunately_ this is one of those topics that might be a little _too_ involved for Dr. Lincoln's style of video. I'm not sure if it can be covered in 10-20 minutes... but maybe. He's very good at breaking complex stuff into bite-sized chunks, after all!
In short, though, to even begin talking about it, you have to get very specific about what you _mean_ by "size" at that scale. If what you mean is functional, viable assumptions to be able to do theoretical work, then we can pretty safely assume in almost all circumstances that electrons are point particles.
If what you mean is what we can actually _measure_ (in principle), then interactions between the method of measurement and the particle become highly non-trivial. Meaning as you narrow in closer and closer to the levels of probing energy that are capable of _resolving_ something as small as an electron, your probe also has enough energy to _change_ it, to create a sea of virtual particles near it that make it "fuzzy" in a sense; not in the sense of the image through a lense that's not focused right being "blurry", rather the electron _itself_ ceases to even _have_ a well-defined "size".
Not coincidentally, this uncertainty in its determinable, measurable size fits nice and neatly into what is predicted by the Uncertainty Principle.
Actually, in a way, it _is_ sort of like resolving images... though not through a normal lens, by being out of focus, but rather through a telescope, by being at the diffraction limit.
We're not _there_ yet, with electrons... but we have placed constraints on their size. IIRC, our current constraint says that electrons can be _no bigger_ than about 10^-18 meters, or an attometer.
Any particle which exists at a point would have unbound momentum.
Light is a 2 dimensional wavelet as it can only oscillate in a single plane & is locked at the speed of light. The size of its existence in a plane is dictated by its wavelength.
Dear Dr. Lincoln,
Regarding the possible decay products of the proton in this illustrated example, wouldn't the proton also create an electron-neutrino along with positron and neutral pi-meson?
I'd really appreciate your thoughts regarding it. And, thank you for an engaging explanation!
That particular class of proton decay requires the hypothetical X boson to allow violation of the baryon number, converting a quark into the positron, which involves no neutrino emission.
@@tonywells6990 sure it doesn't require the hypothetical Y boson. Or Z boson?
@@yzfool6639 Y do you ask?
So clear, many thanks, !!
I don't know anything about how this Proton decay will be registered or measured, but if it's such a rare event, will you be sure if you think you found one?
Hoe many positive detections do you need before your conclusion is statistically significant?
A lot. But not an unfathomable amount. IIRC, we only have enough detections at the moment for a 3-sigma result. That means that there's a 99.7% chance that the detections are genuinely of proton decay and a 0.3% chance that we're detecting something else, or random noise.
Typically in fundamental physics, we don't consider something "discovered" until it passes the 5-sigma threshold (99.99994% vs 0.00006%).
Also, only one facility has made the 3-sigma detections, and a discovery requires that at least two independent projects get to 5-sigma.
So... it's a ways off, yet; we'd need at least one more completely independent facility to make at least 5,000 times more detections than the first facility currently boasts, but that's not outside the realm of achievability at all.
More, and bigger, facilities are under construction right now to try to do just that.
In other words, the detections are promising and intriguing enough to compel people to throw a lot more money at it to find out if it's real or not, where before, only modest amounts of money were thrown at the hypothetical possibility.
Essentially, proton decay, today, is pretty much where the Higgs Boson was in 1995. Getting a confirmed result, positive or negative, by sometime in the 2040's, is therefore worth hoping for.
You can look for more information on other neutrino detectors, they all face this same problem of trying to distinguish one event from another.
@@martinklein9489 Yeah, but from what I think it says in the video, proton decay is even more rare. How many do they expect to find in an hour or ... a year?
Let's hope the scientist on duty wasn't blinking or having a smoke break when it finally happens.
Ahh Fermilabs... I came for the science, I stayed for the t-shirts. ^_^
I just came from Sabines video about particle physicists. It's changed how I viewed this video tbh, not completely but still, there's a lot to think about here that isn't just the physics.
Proton decay could mean that protons and electrons can arrise from quantum fluctuations without the antimatter counterpart, which would explain why we can't find antimatter in today's universe (in equal amounts as matter)
It's great to see Dr. Don posting new YT videos again! And I agree that "Physics Is Everything"! 👍👍
I love how quantum/particle physics explains natural behavior in terms of the conservation of a quantum property. As if that is an explanation. That's merely a description of "what" is happening, with no details of "how".
I would bet on the protons being stable. The standard model will probably last quite a long time
So what are the technical reasons why a lot of space in DUNE goes unused? Maybe say more about the design of the experiment?
Probably because it was mostly designed for studying neutrinos, looking for proton decay is just something it happens to be able to do
I love this channel so much, thank you for all theses videos!
What if energy is added to the proton so that it could decay into something heavier? Like a neutron or one of those other baryons that were mentioned but not described at least by timestamp 9:59? Or if energy is needed to make a proton decay, is that no longer considered decay?
It is no longer considered spontaneous decay. What you describe happens in beta plus decay of atoms, where the proton takes energy from the interaction with the surrounding protons and neutrons.
Sorta the opposite of Sabine's last vid... : ) but, curious anyway what problem decaying protons is supposed to solve?
Yes, at least they dont build this lab for the sole reason of confirming unneccesary unwarranted theories.
Does Baryon number conservation result from any fundamental symmetry of the Universe?
Could we make these protons age much faster? Say in a particle accelerator?
Fermilab rocks.
You are such an sympathic and excellent lector! I would call you, just like Anton Petrov does, a wonderful person :-)
Hello wonderful person!
Given that dark energy is associated with negative mass, shouldn’t a proton decay into a neutron and some dark energy particles be allowed in the standard model?
What does that tell us about dark energy since we have never detected proton decay? I assume it at least puts some constraints on dark energy?
I assume if new experiment is not detecting decay you will again increase predicted decay time and start building even bigger detector. But is it justified providing that there is theory that does not need protons decay?
But there isn't one. The standard model is incomplete.
I use this topic as a bonus problem in the intro to particle physics section of my class. I give them the Feynman diagram and ask them some questions about it like what conservation laws are violated, is the X or Y boson charged? If so what’s its charge? Etc.
This guy is seriously cool - he's like the James Dean of Physics
Please refrain from feeding Proton Don's adorable ego.. thank you kindly. 😊
I think he's the Chuck Norris of Physics, but thas just me.
An age-gap mishap to be sure; neither sulk nor surrender,@@likebot. , your spot at the cool kids table is immutable as the proton almighty.
Do heavy quarks like the strange quark decay and if so into what?
"That sounds like a lot, but it's more than that" is a great line.
How is baryon number conserved during proton on proton collisions? Are mesons and anti-mesons created during the collision, thus conserving baryon number?
The baryon number in proton proton collisions is strictly positive(+1 for each proton), so you have to produce more baryons than anti-baryons.
@@narfwhals7843 And how is that accomplished? What end products are produced as a result of the collision?
Isn't this like saying "if we find ghosts it would revolutionize our understanding of the world, and we would need to rewrite the entire periodic table".
And then use tons of money looking for ghosts finding machine?
First step should be to have any reason to believe ghosts exist in the first place, then start looking for ghosts.
If there isn't any reason to think proton decays, and our theories also predicts it doesn't decay, and one has spent tons of money checking that it doesn't decay - then maybe it just doesn't decay. Until we have a real observational reason to believe it decays, then maybe move on to something more useful science?
I don't think so. A bigger machine incorporates more events, that's the key. At some point you have considered enough events to make a decision. So far the detectors have not been of a size to make a decision. So bigger than what we have, but only because we have not gone big enough for proof.
@@fps079 Isn't this an ever extensible argument? We can always claim "Well its not big enough that's why", couldn't we?
both super-kamiokande and dune have multiple scientific goals, they are neutrino detectors that can also search for proton decay for the same price
@@fps079 - but there is nothing in our theories saying protons does decay, no is there?
First you need an observation that can better be explained by proton decay, than not. Then you check.
You don't start postulating that "if protons decay then cool".
Its the same as saying "we've not looked for ghosts on the back-side of Jupiter, we should build a billion dollar probe to check".
And when it doesn't find it, just say "we've not looked for ghosts on the back-side of Saturn, we should build a multi-billion dollar probe to check".
@@neut9270 - which is fine, as long as the other science is based on something other than hunting for ghosts.
Here is a question I have: How long is the present ? What can we infer from the response ?
The presence is now. Time moves forward.
Sabine Hossenfelder has a video about challenges to the Standard Model that was published recently.
What was the reasoning behind the baryon number having to be conserved? Why is/was a baryon thought to be unable to split into 3 mesons?
It would require the simultaneous production of three anti-quarks.