[HN Gopher] Large Hadron Collider discovers three new exotic par...
___________________________________________________________________
Large Hadron Collider discovers three new exotic particles
Author : geox
Score : 612 points
Date : 2022-07-05 11:58 UTC (11 hours ago)
(HTM) web link (home.cern)
(TXT) w3m dump (home.cern)
| mrlonglong wrote:
| So if atoms are composed of electrons, protons, and in turn
| electrons, protons are composed of these particles, can we
| potentially drill down a bit deeper into these hadrons, might
| they be composed of further sub particles yet unknown to science
| yet?
| drexlspivey wrote:
| That's the premise of string theory
| centilliard wrote:
| Based on this comment on reddit [1], it looks at some point one
| needs to use the mass of a solar system.
|
| [1]
| https://www.reddit.com/r/explainlikeimfive/comments/vri4ih/e...
| davrosthedalek wrote:
| As far as we know, both leptons (electrons, positrons, muons,
| taus) and quarks are fundamental, i.e. not composed out of
| other particles (also, they are pointlike, i.e. they have no
| extend). That's not true for protons (which are made out of
| quarks and gluons. It's a little bit complicated because of
| vacuum polarization, but if you count a certain way, you'll
| find it's composed out of two up and one down quark). They also
| have a measurable size.
|
| These new particles are also made from quarks (4 for the tetra
| quark and 5 for the pentaquark), and they also have a size.
| ars wrote:
| It's not known if quarks are fundamental, nor is it known if
| they are pointlike.
|
| We've never seen a free quark, so we just don't know.
| davrosthedalek wrote:
| Doesn't have to be free to be studied. We can do deep
| inelastic scattering to measure the quark shape, the same
| way we can do quasi-elastic scattering to study the neutron
| shape. SM certainly assumes leptons and quarks to be point-
| like. (of course, in general, we can not prove any theory,
| only disprove.)
| ars wrote:
| Deep inelastic scattering of the nucleus did not find
| quarks. It only found nucleons.
|
| The same thing here: it's not known if quarks have an
| internal structure. And unless your energy is higher than
| the size of the object being measured you certainly can't
| tell if it's point like.
| tonymet wrote:
| whatever they did 10 years ago opened up pandora's box . can we
| please return to the pre kony 2012 timeline ? Ever since Harambe
| died it's been a total apocalypse
| sylware wrote:
| Allright, at high energy, the LHC manages to observe some
| particule configuration never seen before. Anything to "milk"
| something interesting from those?
| logicalmonster wrote:
| Given that all of these exotic particles that are apparently
| discovered are extremely short-lived (at the limits of human
| technology to even register them) is it possible that scientists
| are radically misinterpreting the meaning of these experiments
| and finding particles where there's some other force or phenomena
| being observed? I'm very skeptical that it's apparently just
| smaller and smaller particles all of the way down, and every time
| they get bigger and badder technology to collide atoms, they tell
| us that they coincidentally discover new particles. What if
| everything here about reality is being misinterpreted?
|
| Here's an analogy that might not make sense to everybody, but to
| me, this feels a bit like the famous memes from the Chernobyl
| movie. "3.6 Roentgen. Not great, Not terrible." where the real
| answer about the radiation exposure was radically different. Some
| the people tasked with coming up with that 3.6 answer might not
| have had a bad intent, but they were at the limits of their
| technology to provide an answer and radically misinterpreted what
| they were seeing partially because of that.
| tooltower wrote:
| The new particles in this case aren't "smaller" than the ones
| we already know about. They are short-lived because they are
| heavier. They quickly decay into something simpler.
|
| Extraordinary claims need extraordinary evidence. This article
| doesn't really describe anything that unexpected. It's not that
| hard to believe.
| CoastalCoder wrote:
| Question from a non-physicist: In this context, what does it
| mean for something to be a "particle"?
|
| I.e., if I see some feature in the LHS data, what makes me call
| it a "particle" vs. some other concept / object / phenomenon?
| lisper wrote:
| These aren't really "discoveries". These particles were already
| known to exist (or, to be precise, whose existence was
| predicted by the Standard Model, just like the Higgs boson).
| This is just the first time they have actually been observed.
| The headline is misleading, but the first sentence in the
| article gets it right:
|
| "The international LHCb collaboration at the Large Hadron
| Collider (LHC) has observed three never-before-seen particles."
| ClumsyPilot wrote:
| I think I would be very happy to be the first person to
| observe a new particle, its discovery enough for me :) It
| does not need to appent all of known physics or be unexpected
| for us to call it a discovery
| lisper wrote:
| I get what you're saying, but it's not like someone looked
| through a microscope and actually saw one of these things
| for the first time. It's computers crunching trillions of
| data points and spitting out a result. So it's not clear
| who "the first person to observe this" actually was.
| HansHamster wrote:
| > These aren't really "discoveries". These particles were
| already known to exist (or, to be precise, whose existence
| was predicted by the Standard Model, just like the Higgs
| boson). This is just the first time they have actually been
| observed.
|
| But doesn't that make it a discovery? Sure, a discovery of
| something already predicted by the Standard Model, but unless
| it has been observed, we just don't know for sure if it
| actually exists. The Standard Model just has been very
| successful at predicting stuff :)
| lisper wrote:
| To my way of thinking one of the defining characteristics
| of a _discovery_ is that it is _unexpected_ , so a
| confirmation of a theoretical prediction doesn't count.
| deelowe wrote:
| Isn't that a bit like saying the atom was not truly
| discovered until scanning microscopes were put to use?
| k__ wrote:
| I think the process is:
|
| Scientists make a theory.
|
| The theory predicts a bunch of particles.
|
| Scientists build LHC to check if the theory is right.
|
| LHC finds the predicted particles.
|
| The theory was right.
| nxpnsv wrote:
| Except it is not a single theory, but whole families of
| theories.
| [deleted]
| killerstorm wrote:
| Currently the best known theory of physics at small scales is a
| quantum field theory known as the Standard Model.
|
| "Particles" are phenomena which appear when fields are
| quantized. They aren't really balls of stuff. E.g. photon is a
| quantum of a wave in electromagnetic field.
|
| These exotic particles are simply a confirmation of predictions
| made by the Standard Model, they are not surprising, it's just
| the first time there was enough data to test this particular
| prediction of the theory.
|
| > I'm very skeptical that it's apparently just smaller and
| smaller particles all of the way down
|
| The Standard Model was formulated in 1970s, no principally new
| phenomena were discovered since. So it's been strong for ~50
| years.
|
| It's known to be incomplete as it does not explain gravity, and
| physicists hope that better theories will be found in future.
| But so far nobody was able to formulate a theory which would
| make better predictions than the SM.
|
| > What if everything here about reality is being
| misinterpreted?
|
| The topic of physics is to build models which predict observed
| phenomena. Knowing what reality _is_ is a topic of philosophy
| and religion.
| jeremyjh wrote:
| Your analogy is poor because the "3.6 Roentgen" was a story the
| politicians were telling each other; where the actual scientist
| knew they were measuring the limit of their equipment. Perhaps
| it's uncharitable but I feel like I could restate your question
| as: "I know nothing about particle physics - is it possible the
| entire field is just cranks deluding themselves?"
| jfjrkkskdik wrote:
| jacobr1 wrote:
| Should that question be asked of the string theorists
| instead?
| StanislavPetrov wrote:
| >is it possible the entire field is just cranks deluding
| themselves?
|
| That's a question better saved for psychiatry and sociology.
| mkr-hn wrote:
| I assume this isn't from the run that started today.
| fnands wrote:
| Definitely not.
| stjohnswarts wrote:
| I'm pretty sure they go over their data for quite a while
| before confirming new particles, so no it wasn't today's run.
| coldcode wrote:
| Physics is not my thing, but I love that the more is discovered,
| the more is discovered that there is more to discover.
| GartzenDeHaes wrote:
| To quote Alan Watts, "There is no end to the minuteness that you
| can unveil through physical investigation. For the simple reason
| that the investigation itself is what is chopping things into
| tiny little pieces. And the sharper you can sharpen your knife,
| the finer you can cut it. And the knife of the intellect is very
| sharp indeed. And with the sophisticated instruments that we can
| now make, there's probably no limit to it."
|
| It's almost as if we're looking at a continuous functions that
| can generate an infinite number of discrete segments.
| nxmnxm99 wrote:
| Not surprising you're downvoted on HN, but your comment is the
| only one that makes sense in this entire thread. I wonder at
| one point our collective consciousness will wake up to the fact
| that we've completely hit a wall in our understanding of the
| universe, and that spending billions detecting more particles
| isn't magically going to explain reality.
| timbit42 wrote:
| Let's keep going until we figure out how to harness gravity.
| formvoltron wrote:
| So.. maybe it's a good time to pause the collider and see if we
| can use this discovery for any practical purpose. If not, that
| money could go towards clean energy research or lab grown meat
| research, anti cancer or anti aging research... something that
| might do people some good.
| 4khilles wrote:
| I think a species of 7.8 billion individuals can afford to do
| things in parallel.
| croes wrote:
| So crisis averted?
|
| https://news.ycombinator.com/item?id=30516078
| Koshkin wrote:
| I wonder if this discovery constitutes "new physics" to any
| degree.
| lamontcg wrote:
| No, not "fundamentally". This all fits within the framework
| of QCD.
|
| Like the wikipedia article on pentaquarks says, a five-quark
| bound cluster was considered by Gell-Mann back in 1964.
| layer8 wrote:
| Nope. It just further confirms decades-old predictions within
| the Standard Model of particle physics:
| https://en.wikipedia.org/wiki/Pentaquark
| alberth wrote:
| Off topic: what's the convention on what your root is for a
| branded TLD?
|
| I see CERN is using "home.cern".
|
| Google has ".google" but I'm not sure what the root is since they
| have many.
|
| What's the convention for the root of a companies branded TLD?
| macspoofing wrote:
| who ordered that?
| dkural wrote:
| The Standard Model did, in the 50s.
| frutiger wrote:
| This is a reference to the famous quip by Rabi:
|
| > The eventual recognition of the muon as a simple "heavy
| electron", with no role at all in the nuclear interaction,
| seemed so incongruous and surprising at the time, that Nobel
| laureate I. I. Rabi famously quipped, "Who ordered that?"
|
| https://en.m.wikipedia.org/wiki/Muon
| ncmncm wrote:
| Which is itself a reference to eating at a Chinese
| restaurant, and a dish is brought to the Lazy Susan nobody
| recognizes.
| high_byte wrote:
| I love this.
| nonrandomstring wrote:
| Things I didn't get from article:
|
| What changed to make a slew of new discoveries possible? Is it
| pure chance like Bitcoin mining? If so, what's the chance of
| discovering nothing for years and then, like London buses, three
| all come along at once?
|
| What are the implications of a new "particle zoo"? Can I do
| anything with these, like build new atoms, or use them to detect
| something?
| letmeoknmmm wrote:
| > If so, what's the chance of discovering nothing for years and
| then, like London buses, three all come along at once?
|
| Means we are in a pretty tricky timeline.
| stevenwoo wrote:
| There's another article floating about how they increased
| energy of collisions recently at LHC.
| https://www.nature.com/articles/d41586-022-01388-6
| dicknuckle wrote:
| Fairly sure this was scheduled to happen today, July 5th.
| legohead wrote:
| Cool results considering the recent article I saw on HN
| suggesting there's not much else to find [1].
|
| [1] https://bigthink.com/hard-science/large-hadron-collider-
| econ...
| davrosthedalek wrote:
| They came together most likely because they were detected in
| the same/similar analysis. There are probably hundreds of
| analysis performed in parallel on the LHCb data sets, by
| different sub-groups of the collaboration, looking at different
| reactions / channels etc. It could also be that they grouped
| several results together because they are similar. There is
| always an internal review process, and committee meetings (for
| the final "go ahead, publish") can impose a granularity on the
| time of release. Could also be that the paper is already on the
| arXiv for days, and this is just the common press release.
| hypertele-Xii wrote:
| Think of it like taking series of blurry photos of an unknown
| object. A single photo just looks like a blob, but accumulate
| enough of them and apply some algorithmic magic and eventually
| the picture sharpens.
|
| When particles are collided and the result measured, there's
| probably lots of noise in the data. In a single picture, a
| single pixel (datapoint) tells you nothing. But capture enough
| results, and you can begin to filter the noise out, revealing
| patterns underneath.
| chicX wrote:
| The change is the gradual accumulation of statistics. These are
| relatively rare events. The LHC has been running, high-energy
| proton-proton collisions have been occurring, and the LHCb
| detector in this case has been measuring them. The statistics
| increase, and eventually the characteristic peaks of short-
| lived resonances can be identified above the noise of
| "background" collisions.
|
| I think the goal of this work is to understand the nature of
| the strong force. Quantum chromodynamics (QCD) is pretty
| difficult as far as quantum field theories go, its strongly-
| coupled, meaning making first-principles predictions of what to
| expect is really tough. Its a huge computational effort being
| run on some of the biggest computers on the planet (lattice
| QCD).
|
| We observe that all the hadrons in experiment are "colour
| singlets" meaning that the colour charge of QCD is hidden.
| These are usually three-quark states (protons, neutrons, etc)
| or quark-antiquark states (pions, kaons, etc). There are many
| other ways of making "colour singlets". For example, these
| tetra and pentaquark combinations. There are also "hybrids"
| made of a gluon and some combination of quarks. There is some
| evidence on both experimental and theoretical sides for at
| least a few of these hybrids. Glueballs are also possible,
| states made entirely of gluons, but there is only really
| theoretical evidence for these so far in specific limits. We
| just don't know if they exist in reality.
|
| Everything is made of this stuff. Most of the mass around us
| comes from the strong interactions. It's important to
| understand it.
| parineum wrote:
| > The change is the gradual accumulation of statistics. These
| are relatively rare events. The LHC has been running, high-
| energy proton-proton collisions have been occurring, and the
| LHCb detector in this case has been measuring them. The
| statistics increase, and eventually the characteristic peaks
| of short-lived resonances can be identified above the noise
| of "background" collisions.
|
| I think people are a bit spoiled by the Higgs
| leak/announcement/discovery timeline. I'm sure those in the
| know have known about this discovery for some time but, like
| you said, it takes some time to gather enough data to be
| confident (and to qualify as the mathematical standard set
| for "discovery").
| ncmncm wrote:
| Right, after the bump reaches 3x sigma they have some
| confidence it deserves their own attention, and at 4x they
| are sure, but the rule is you don't publish until you have
| enough data for a 5x sigma result, which just takes a lot
| more data and a lot longer.
|
| "Sigma" here refers to standard deviations off the Gaussian
| normal mean. Zero means completely random. In psychology
| they publish at 2x sigma, 95%, which means 20:1 odds
| against a spurious result, and they publish a _lot_ of
| spurious results because you can generate an unlimited
| number of hypotheses. In physics, things are considered
| more deterministic, and an experiment doesn 't need to
| recruit undergrads to be data points, so you run your LHC
| for a few more months and avoid wasting people's attention.
| huijzer wrote:
| The chance of falsely rejecting the null hypothesis
| increases as you gather more data. Put more simply,
| finding something that differs "significantly" from some
| distribution becomes easier as you gather more data.
| Imagine having only 3 psychology student in a study, the
| required effect size has to be huge for the test to say
| that it is significantly different.
|
| However, the approach taken by CERN is of course right.
| They find a result at a certain significance level and
| then collect more data to verify the result. As long as
| there aren't thousands of simultaneous verifications
| running, this approach is sound. Obviously yes,
| physicist's know what they're doing.
|
| Having said that, please don't read this comment as me
| approving of frequentists statistics. Bayesian or cross-
| validations are way easier to interpret where possible.
| cryptonector wrote:
| Probably also just time: time to run more experiments, time
| to improve analysis compute capability, and to analyze new
| data and re-analyze the data they already have. These
| experiments yield enormous amounts of data.
| ijidak wrote:
| Thank you for this explanation.
|
| Follow-up question. Why don't quark anti-quark combinations
| self annihilate?
|
| I've been trying to understand this.
| whatshisface wrote:
| The particles are very shortlived, so the brief answer is
| that they do.
| chicX wrote:
| They do. The Tcs0 tetraquarks don't have quark-antiquark
| pairs however, you see from the article and figures, that
| the quark content is charm + anti-strange + up + anti-down,
| these can't annihilate because the quarks have different
| flavours. They can "annihilate" via the weak interactions
| though, which can connect quarks and anti-quarks of
| different flavours. For example the charm-antistrange part
| could decay via a W-boson to a positron and a neutrino.
| This is a much slower process however.
|
| In the pentaquark, charm-anticharm annihilation can and
| will happen. The time for charm-anticharm annihilation is
| usually slower relative to light and strange hadronic
| interactions though. In part because the strength of strong
| interactions reduces at higher energies, and the charm
| quark is more massive and so the relevant energy scale for
| the decay is higher.
|
| One charm-anticharm resonance, the J/psi(3097) is very long
| lived even though the quarks can annihilate. In many
| theoretical models of these things, its often treated as a
| stable particle.
| nonrandomstring wrote:
| Thanks for trying to explain. It's all still largely beyond
| me TBH.
|
| But more idiot's questions if you have any thoughts....
|
| My understanding was that particle accelerators were being
| used to try and deconstruct matter, to do for want of a
| better word "fission" by smashing things together and seeing
| what smaller bits came out - by analogy to mass spectrometry.
|
| What seems to be going on now is that we're trying to make
| new particles. Have we switched to a sort of "fusion" - to
| see if smashing things together will get them to stick in
| bigger configurations?
|
| Have all the most fundamental bits (quarks?) been found now?
| Can we prove that those are irreducible?
|
| chreers
| richardwhiuk wrote:
| Essentially, you smash particles together. When you do so,
| they will give off a bunch of energy.
|
| That energy forms into a bunch of particles, each of which
| will then decay into less esoteric particles.
|
| We have no proof (and it's probably impossible to do so),
| that anything we've found is fundamental.
| omegalulw wrote:
| How do we even know that the universe has fundamental
| particles?
| Zamicol wrote:
| The Planck constant appears fundamental.
| michaelfeathers wrote:
| It may not.
|
| https://en.wikipedia.org/wiki/Gunk_(mereology)
| adamrezich wrote:
| > We have no proof (and it's probably impossible to do
| so), that anything we've found is fundamental.
|
| this entire discussion is fully outside of my knowledge
| wheelhouse but why should we believe that the universe is
| anything less than infinitely fractal at the micro scale?
| like you said, how would we even know if something is
| fundamental?
| platz wrote:
| > why should we believe that the universe is anything
| less than infinitely fractal at the micro scale
|
| And what basis does that claim rest on
| adamrezich wrote:
| sheer intuition based upon the adage "you don't know what
| you don't know", repeated incorrect assumptions that
| we've finally discovered fundamental building blocks of
| reality, and lack of capacity for imagination (sorry--I
| tried!) for what the discovery of absolutely positively
| _provably_ fundamental building blocks of reality could
| even potentially look like
| platz wrote:
| I disagree. Not that you're wrong but that you're right.
| adamrezich wrote:
| ???
| ijidak wrote:
| > We have no proof (and it's probably impossible to do
| so), that anything we've found is fundamental.
|
| This is a good statement.
|
| I've seen many online state that quarks are fundamental.
|
| There is no way we can make such a definitive statement.
|
| Quarks may be not be fundamental.
| shmoe wrote:
| What would it take to actually prove that they are? I did
| miss the "impossible" above when first posting this --
| but pretend it isn't?
| ncmncm wrote:
| This is the problem String theorists have.
|
| We will never, in the lifetime of anybody who guesses we
| ever existed, be able to build an accelerator powerful
| enough to check whether it is right about gravity. So,
| they potter and try to show this or that family of
| variations (among 10^500 imagined) does or doesn't
| contradict details of the Standard Model we have most
| confidence in.
| baremetal wrote:
| it would require being able to generate a high enough
| energy beam
|
| But using current accelerator technology it would require
| an accelerator many times the size of the earth, _many_.
|
| I use to work at a particle accelerator, part time, when
| i was in college. Fun fact i once confirmed Einsteins
| photoelectric effect using a high energy x-ray beam, a
| copper target, and high voltage.
| adregan wrote:
| I believe it's due to the fact that after several years of
| upgrades, they started running it today at much higher power
| (13.6 trillion electronvolts).
| Quinner wrote:
| They would definitely not be publishing results of the power
| increase on the same day of the increase. These experiments
| take a lot more time than a day to perform and analyse.
| swader999 wrote:
| Or time travel. That's a lot of power they just added.
| benreesman wrote:
| The top few comments are reasonable but not written by ATLAS
| folks: what's the layman's takeaway by an expert?
| davrosthedalek wrote:
| This is from LHCb, not ATLAS ;)
| benreesman wrote:
| I think I lowered the bar a bit on "layman" there but I
| difinitely got critical expert information ;)
|
| Well done sir.
| FabHK wrote:
| Could someone put this in context?
|
| Is this big news that could lead physics out of its long stasis?
| Or "just" relatively small details?
| bradrn wrote:
| I'm no particle physicist, but this doesn't look like anything
| too fundamental -- no new _elementary_ particles, just some new
| and interesting combinations of existing elementary particles
| (in this case, quarks). It might have lots of further
| relevance, but it might not just as easily.
| throwawaymaths wrote:
| They are not elementary particles, just permutations of a
| higher number of quarks.
| nxpnsv wrote:
| "just"
| gus_massa wrote:
| Closer than business as usual. The problem to get out of the
| current "long stasis" [1] is to find a new elementary particle
| or an experiment that can't be explained with the current
| elementary particles and can be refined to discover a new
| elementary particle.
|
| They discover two new composite particles. There are hundred of
| composite particles, so it's somewhat business as usual.
| Anyway, most composite particles have 2 or 3 quarks, but the
| new particles have 4 or 5 quarks. So they are weird new
| composite particles.
|
| Making calculations of particles made of a few quarks is very
| difficult, borderline impossible, so it's interesting to find
| new particles and verify that the current approximations for
| particles made of a few quarks are good enough or fix them.
|
| Also, the approximations for particles made of a few quarks use
| virtual particles that appear and disappear. And some of these
| virtual particle may be a unknown new particle. So if the
| calculation is too wrong it may be an indirect way to discover
| a new elementary particle and escape the "long stasis". But I'd
| not be too optimistic about a groundbreaking discovery.
|
| [1] I don't think it's a problem yet. The current "long stasis"
| it's overrated IMHO.
| fhars wrote:
| What makes these kind of particles interesting and "exotic"
| is that they are not the kind of particles the Standard Model
| was originally developed to describe. Those particles, mesons
| and baryons, consist of two and three quarks, respectively,
| with some quantum numbers that must obey certain rules for
| the particles to exist, and we have found that (almost?) all
| of the two and three quark combinations allowed by the rules
| are in fact observable as particles in experiments.
|
| But those rules for the quantum numbers can also be fulfilled
| with certain combinations of four or five quarks, and there
| is nothing in the Standard Model that either forbids or
| requires these combinations to exist as real particles. So it
| was new information when the first resonances that could be
| interpreted as those kind of particles were discovered and it
| is interesting that there are more of these. But it is not
| unexpected, either, the earliest paper on pentaquarks cited
| on the wikipedia page is from 1987.
|
| So it is indeed close to business as usual. It is
| interesting, and new, but is is still filling out the corners
| of the Standard Model.
| tux3 wrote:
| Is it possible, even it principle, that some of these exotic
| hadrons could be long-lived (let alone stable)?
|
| They're probably interesting to study on their own, but the
| engineering instinct is to want to build something out of them,
| or use them as tools, which seems pretty hard if they
| disintegrate in a quintillionth of a second!
| aqme28 wrote:
| Typically no, because higher energy collisions exist naturally
| with cosmic particles, so we would have _probably_ observed
| some of these stable particles by now. But in practice they
| could be rare and hard to detect.
| Enginerrrd wrote:
| I'm not even sure if "typically no" is justified here. We
| don't know what dark matter is, but we do know that it
| appears that there's a lot of it out there. You could
| definitely do some math and maybe if you were really clever
| about it relate the quantity of it that exists to exclude
| some particular energy range of interactions, but I don't
| think that's been done.
| zeroonetwothree wrote:
| The whole point of "dark matter" is it can't be made of
| normal matter (ie quarks).
|
| (It might not even exist, after all...)
| zamalek wrote:
| WIMPs, were they to exist, would consist of regular
| matter.
| shagie wrote:
| https://en.wikipedia.org/wiki/Weakly_interacting_massive_
| par...
|
| > There exists no formal definition of a WIMP, but
| broadly, a WIMP is a new elementary particle which
| interacts via gravity and any other force (or forces),
| potentially not part of the Standard Model itself, which
| is as weak as or weaker than the weak nuclear force, but
| also non-vanishing in its strength.
|
| That's not regular matter.
|
| Its MACHOs that are made up of regular matter (well,
| brown dwarfs and black holes).
|
| There are also theories that put an undetected form of
| neutrino as dark matter which would be a bit more
| regular.
| kadoban wrote:
| > That's not regular matter.
|
| > Its MACHOs that are made up of regular matter (well,
| brown dwarfs and black holes).
|
| I mean...isn't this "technically correct" on a level
| that's beyond even the usual extremes of pedantry? Or
| maybe I'm missing something?
|
| There's no cheese in my fridge, only blocks of cheese
| that are made up of cheese...
| lamontcg wrote:
| The person who started off this comment thread made a
| sloppy reference to "normal matter (i.e. quarks)". That
| statement should be read in good faith as meaning the
| existing known elementary particles as "normal" matter.
| That implies that some particle which only interacts via
| gravity and some unknown force is not included in
| "normal" matter.
|
| To twist that by claiming such a particle would still be
| viewed as matter just like all the rest of the matter
| that goes into the stress-energy tensor is where the
| pedantry started in this thread. The original statement
| is pretty clear in its intent. The pedantic reading that
| followed that comment results in "normal" matter just
| being all matter by definition and hence "normal" is
| redundant since there can't be abnormal matter. That
| clearly isn't what the first comment intended since they
| actually meant something by "normal".
| gamblor956 wrote:
| No, a WIMP is the theoretical dark-matter equivalent of a
| particle.
|
| A MACHO is a low-energy star or whatever that would
| explain the apparent presence of dark matter without
| actually requiring anything exotic like WIMPs. The idea
| is that these objects are (relatively) massive, numerous,
| and so low-energy that they are hard to detect and their
| combined mass would theoretically explain the effects we
| currently attribute to dark matter.
|
| Or in other words, a WIMP would be like claiming that
| your fridge is disintegrating your cheese, and a MACHO
| would be the kid raiding the fridge for cheese at
| midnight when you're asleep.
| at_a_remove wrote:
| No.
|
| If a particle _can_ decay into a lighter set of particles and
| still obey all of the conservation principles, they will. The
| heavier they are, the more they 're going to decay and the more
| "options" they have to decay. An electron isn't going to do
| anything because there is nothing lighter than an electron that
| still carries charge, etc. Something much heavier, like a free
| neutron, will fall apart into a proton, an electron, and an
| anti-electron neutrino.
|
| These particles have _options galore_ as to what they can fall
| apart into being, and so they do, and with great haste.
| wesammikhail wrote:
| I know nothing about physics as it is not my domain. So I
| don't know if what you're saying is true or not. But if it
| is, I find that notion somewhat poetic.
|
| For the sake of my own edification, I'd like to follow this
| up with a few somewhat seemingly dumb questions if you dont
| mind:
|
| Is it the case that a given particle is trying to settle into
| a "lowest energy state" possible? I am not using physics
| terms here. More like conceptually, are these particles, due
| to the number of options available to them, decaying into the
| lightest stable variant allowed by the laws of physics? if
| that is the case, then could we perhaps find ways to engineer
| structures within which these particles last for a whole lot
| longer than they should (on a human timescale)? And what is
| stopping us from doing that? is it the energy cost associated
| with such a structure/device or is there a more fundamental
| reason we cant do that?
| at_a_remove wrote:
| More or less.
|
| Sometimes they will have intermediates, which then decay,
| and then those products decay, and so on. That's quite
| common. Eventually they just ... fall apart. The more
| options, the faster. The greater the energy stepdown, the
| faster, by which I mean "can it release a gamma? Or fall
| apart into some much smaller things?"
|
| However, it is independent of "nearby" structure, where
| nearby is any distance larger than the nucleus. So, no, we
| cannot contain these particles within anything to prevent
| their decay, it is like trying to build a bouncy castle
| around a hand grenade in hopes that it won't go off.
|
| Note that there is an _apparent_ delay in decay, from our
| perspective, when particles are moving very fast, like a
| relativistic muon lasting longer (although still a very
| brief period of time by our standards) than expected,
| simply due to special relativity. But here this also would
| not help.
|
| Things fall apart, the center cannot hold, and so on.
| holmium wrote:
| As another not-physicist who is interested in physics, I've
| found the articles/explainers at Of Particular Significance
| very helpful. There are a few on particle decay, and I
| think that these two provide a longer answer to your
| questions:
|
| Most Particles Decay -- But Why?
|
| https://profmattstrassler.com/articles-and-posts/particle-
| ph...
|
| Most Particles Decay -- Yet Some Don't!
|
| https://profmattstrassler.com/articles-and-posts/particle-
| ph...
|
| Neutron Stability in Atomic Nuclei
|
| https://profmattstrassler.com/articles-and-posts/particle-
| ph...
| samstave wrote:
| (I' in the exact same boat as you)
|
| ---
|
| >> _trying to settle into a "lowest energy state"
| possible?_
|
| What if its actually the reverse: Its attempting and
| succeeding to be the most it can be given the eddy of
| forces around it - the particle is "becoming" - not
| "falling apart"
| sethhovestol wrote:
| It is the case that particles always try to settle into the
| lowest energy, and the more options they have the faster.
| We may be able to engineer places where they're stable,
| like in the example from my grandparent of a neutron. They
| are unstable since their mass is greater than the mass of a
| proton and an electron combined, but they're stable in all
| common elements we're used to. So much so that we think of
| radioactive elements as the exception, but (mostly) all
| that's happening there (in beta decay) is a neutron
| decaying. I'm not an expert, but I'd imagine making a
| stable situation for a heavier particle much harder than
| just making an atom, and the fine grained control is even
| hard still.
| chriswarbo wrote:
| > Is it the case that a given particle is trying to settle
| into a "lowest energy state" possible?
|
| It's more accurate to think of the energy "spreading out"
| (remember that mass is a form of energy too, since E=mc^2).
| The energy can rearrange (subject to conservation laws),
| between being one massive particle, or several lighter ones
| (in fact there's a superposition of possibilities, because
| quantum).
|
| _In principle_ the probability of switching back-and-forth
| is equal, e.g. the probability of particle A decaying into
| a B+C pair, is identical to the probability of a B+C
| collision producing an A. However, most of the directions
| those light particles can take will result in them _flying
| apart_ rather than colliding; that spreads out the energy,
| so it can no longer switch back into the massive particle
| configuration.
|
| Note that this is essentially the first and second laws of
| thermodynamics (energy is conserved, and concentrations
| tend to "spread out" over time)
| lisper wrote:
| These are great questions!
|
| > Is it the case that a given particle is trying to settle
| into a "lowest energy state" possible?
|
| Not exactly. Energy is conserved during these decays. In
| fact, energy is conserved during all physical processes, so
| the "lowest energy state possible" is a little bit of a
| white lie. What makes it a white lie is that it is a very
| good approximation to the truth for thermodynamic systems,
| i.e. systems consisting of large numbers of particles. But
| for quantum systems, it is no longer a good approximation.
| In quantum systems, what happens is that you have a wave
| function that describes all of the possible states a system
| can be in. The more mass the system contains, the more
| possible states there are in its wave function, and so the
| more likely it is to end up in some state other than the
| one it started out in.
|
| It is even possible for the process of decay to reverse
| itself, and for the constituent particles to come back
| together and reconstruct the original, but for that to
| happen all the constituents have to be brought back
| together, so as a practical matter this never happens
| spontaneously in nature. In fact, that is the whole reason
| for building the LHC -- to make particles (protons) come
| together and make high-mass systems which then decay in
| interesting ways.
|
| > are these particles, due to the number of options
| available to them, decaying into the lightest stable
| variant allowed by the laws of physics?
|
| Not the lightest stable variant, just to one of the
| possibilities described by that particle's wave function.
| These will always be subject to the constraints of
| conservation laws, so the decay products will always be
| lighter than the original. But which particular set of
| possible decay products is actually produced in any given
| decay event is fundamentally random.
|
| > if that is the case, then could we perhaps find ways to
| engineer structures within which these particles last for a
| whole lot longer than they should (on a human timescale)?
|
| No. The wave functions for particles are fixed by nature.
| They are what give particles their identities. They cannot
| be engineered. The only thing that we can engineer is the
| arrangement of particles. Particles are like Lego bricks.
| You can stick them together in lots of different ways, but
| you can't change the shape of a given brick. Sometimes
| quantum Lego bricks fall apart spontaneously, but there is
| no way to control that.
| dotopotoro wrote:
| If neutron is likely to decay into. Why protons dont
| decay while being part of an atom?
|
| (Wouldn't this be example of a structure that prevents
| decaying?)
| davrosthedalek wrote:
| Neutrons don't decay while being part of a stable atom,
| because the atom has actually less energy than the sum of
| the constituents -- the difference is the binding energy.
| Look at deuterium, for example. It has a mass of 2.0141
| u. A proton alone is 1.0073 u, and a neutron is 1.0087 u.
| Deuterium is lighter than the mass of proton + neutron.
| It's also slightly lighter than two protons, so the
| neutron cannot decay without external energy input.
| wyager wrote:
| This is a direct counter-example to the claim that we
| cannot engineer a situation where a particle lasts longer
| than it would in its free state.
| DiggyJohnson wrote:
| This comment caps off an exceedingly educational thread
| of questions and answers.
| at_a_remove wrote:
| No. Protons weigh less than neutrons. What will your
| proton decay into?
|
| Be careful to remember your conservation of baryon number
| when listing your options!
| dotopotoro wrote:
| Edit: If neutron is likely to decay into. Why *neutrons*
| dont decay while being part of an atom? (Wouldn't this be
| example of a structure that prevents decaying?)
| lisper wrote:
| https://profmattstrassler.com/articles-and-
| posts/particle-ph...
| Gerard0 wrote:
| I wished I had a friend like you so I could hear these
| things!
| ngcc_hk wrote:
| I thought in q field theory there is on a fundamentally
| level no particle. They are artificial excite state in a
| field. Hence the all possible state possibly as it is not
| the particle as this is already in a state, but a wave.
| The interaction of fields ... wonder if we reframe the q
| as CSB we have or find new operators to ...
| lisper wrote:
| > I thought in q field theory there is on a fundamentally
| level no particle. They are artificial excite state in a
| field.
|
| That is correct. "Particle" is another one of those
| "white lies."
|
| https://arxiv.org/abs/1204.4616
| H8crilA wrote:
| What kind of haste are we talking about here? Is it
| nanoseconds, or even faster?
| at_a_remove wrote:
| Depends entirely on the particle. A free neutron might have
| a half life of around twenty minutes. These pentaquark
| particles, well, nanoseconds are too long to describe, by
| about ten orders of magnitude.
|
| Some of the heavy elements assembled in colliders are
| described as decaying so quickly that _one_ side of the
| nucleus is coming together even as the other side is
| disintegrating, a sort of brief wave of existence traveling
| at nearly the speed of light across this thing that has
| been forced together and wants to fly apart.
| kibwen wrote:
| Well, technically yes. 0.0000000000001 nanoseconds, to be
| semi-precise. :P
|
| (Or at least, that's the magnitude of a Higgs boson decay,
| about 160 yoctoseconds.)
| H8crilA wrote:
| Lol, that's a lot faster than I thought.
|
| To save some googling: about 10^-22 seconds for a Higgs
| boson decay. Whe a nanosecond, one tick in a 1GHz clock,
| is 10^-9 seconds.
| shagie wrote:
| An example of something considered to be "slow" is the
| muon. You could kind of thinking of it as a heavy electron
| (though that hand waves away a _lot_ ). It has a mean
| lifetime of 2.2 ms - which is fairly slow.
|
| Also note that they're not rare and there's a fair bit of
| neat science behind that too.
|
| > About 10,000 muons reach every square meter of the
| earth's surface a minute
|
| (from https://www.scientificamerican.com/article/muons-for-
| peace/ ).
|
| There's also neat stuff with time dilation and muons (
| http://hyperphysics.phy-
| astr.gsu.edu/hbase/Relativ/muon.html ) - there should be
| far fewer observed muons at the surface if muons didn't
| experience time dilation from their relativistic speeds.
|
| > The historical experiment upon which the model muon
| experiment is based was performed by Rossi and Hall in
| 1941. They measured the flux of muons at a location on Mt
| Washington in New Hampshire at about 2000 m altitude and
| also at the base of the mountain. They found the ratio of
| the muon flux was 1.4, whereas the ratio should have been
| about 22 even if the muons were traveling at the speed of
| light, using the muon half-life of 1.56 microseconds. When
| the time dilation relationship was applied, the result
| could be explained if the muons were traveling at 0.994 c.
|
| (note: mean lifetime and half-life are different numbers)
|
| The thing here is that 2.2 ms is slow, but even with
| something that is that fast (on a human scale), there's a
| lot of neat science that can be done with them. They've
| even made muonic atoms (where the electron is replaced by a
| muon) https://en.wikipedia.org/wiki/Exotic_atom ... and
| _that_ leads to possibilities on lowering fusion
| temperature ( https://en.wikipedia.org/wiki/Muon-
| catalyzed_fusion ) because the muon is much closer to the
| nucleus in its ground state.
| chicX wrote:
| These particles are hadrons held together by the strong force.
| They all contain charm or strange quarks which are relatively
| heavy, and via the weak interactions, they can decay to hadrons
| containing light quarks. Because of the large mass difference
| between the charm and strange compared with the light quarks,
| it's unlikely that any of these will be stable.
|
| Lone neutrons are unstable, they decay in about 15 minutes to
| lighter particles. They have only a few MeV mass difference to
| the stable final state (the proton + electron + anti-neutrino).
|
| For comparison, these particles are 2000+ MeV above their
| ground states so they decay pretty quickly.
| [deleted]
| ClumsyPilot wrote:
| sicne neutrons are stable in a neucleous, is it possible that
| there is any atom-like structure that is stable that contains
| at least one 'abnormal' particle, like a bozon, or any
| 'large' particle made of quarks that is not a proton or
| neutron?
| dariusj18 wrote:
| It'd be cool if they could be created and combined in specific
| combinations and quantities to create new particles that
| wouldn't exist due to natural formation. Sounds like a good
| sci-fi mechanic, creating new particles without the Higgs Boson
| to facilitate FTL or at least some sort of anti-gravity.
| simiones wrote:
| Note that the Higgs Boson has no part in the mass (and
| presumably gravitational interaction) of elementary fermions
| like quarks or electrons, and even less to do with the mass
| of hadrons (whose mass is the mass of quarks + the mass of
| the extraordinary amount of energy sticking the quarks
| together, which dwarfs the mass of the quarks by ~100:1).
| Even if all elementary particles were massless, protons,
| nuclei, and atoms would still have most of the mass they have
| today (though of course many other interactions would be very
| different indeed).
| gnomewascool wrote:
| > Note that the Higgs Boson has no part in the mass (and
| presumably gravitational interaction) of elementary
| fermions like quarks or electrons
|
| This is incorrect -- the coupling with the Higgs field is
| responsible for the rest mass of electrons and isolated
| quarks.
|
| > and even less to do with the mass of hadrons
|
| Yes, this is true -- the contribution of the separate
| masses of the constituent quarks to the mass of hadrons is
| small, like you write.
| jamincan wrote:
| What is the Higgs Boson responsible for if it's not
| involved in the mass of fermions or hadrons?
| simiones wrote:
| The mass of the massive gauge bosons, the W and Z bosons.
|
| Edit: there is an excellent in-depth (but math-light)
| explanation about the Higgs mechanism by Leonard
| Susskind. I highly recommend it if you are interested, it
| lasts about 1h (plus some Q&A) and is extremely
| approachable, while being presented by an established
| authority in the field.
|
| https://www.youtube.com/watch?v=JqNg819PiZY
| gmadsen wrote:
| unless im wrong (im not a physicist) interaction with the
| higgs field does give a none zero amount of mass to
| quarks. but the vast majority of mass of a proton ~99% is
| due to the energy in the gluon field
| willis936 wrote:
| On the surface they might not seem useful, but these
| discoveries develop sub-atomic models, which help predict
| atomic, and in turn molecular, models, which helps materials
| research. There are countless materials we haven't
| discovered/invented yet. We don't know how far we can push it.
| moonchrome wrote:
| > On the surface they might not seem useful, but these
| discoveries develop sub-atomic models, which help predict
| atomic, and in turn molecular, models
|
| If those models had predictive power that translates to
| atomic scale you wouldn't need a multibillion collider to
| prove them.
| paskozdilar wrote:
| If those models didn't have predictive power that
| translates to atomic scale, nobody would give them billions
| for a collider to prove them.
| gus_massa wrote:
| I 99.99% agree.
|
| One of the few molecular level effects that depends on the
| virtual particles that are important in the standard model
| is the Lamb shift https://en.wikipedia.org/wiki/Lamb_shift
|
| In this case the virtual particle is a virtual photon, not
| a virtual weird particle, so it's just scratching the
| standard model.
|
| I'm not sure if the g-2 Anomalous magnetic dipole moment of
| electrons https://en.wikipedia.org/wiki/Anomalous_magnetic_
| dipole_mome... can be measured with a cheap equipment.
| morbia wrote:
| I'm not aware of any predictive power the standard model has
| over nuclear physics and atomic physics directly. In
| principle, yes the standard model _should_ be able to predict
| things at those energy scales, in practice no one has a clue
| how.
|
| To use a more relatable analogy, it's a bit like using
| quantum mechanics to build a skyscraper. In principle it
| should be possible, it practice it is incalculable. Newtonian
| physics does the job fine in that scenario.
| snovv_crash wrote:
| You use the quantum mechanics to design the graphene
| conformation that yield the best loads, and then infuse the
| concrete in your skyscraper with the graphene. Everything
| needs abstraction layers otherwise of course the complexity
| becomes mindboggling.
| dangerlibrary wrote:
| As I understand it, this is not really how most practical
| materials research is done today. Bridging the "scale
| gap" between nano-scale research, micro-scale research,
| etc. up to something the size of a foundation for a
| skyscraper is very hard (read: almost impossible) right
| now. Those nano-scale research areas are pretty siloed
| and only in extreme cases like transistor manufacturing
| is there any meaningful overlap with production use
| cases.
|
| In general, materials researchers for something like
| concrete are going to be better off exploring the (very
| large!) high dimensional space of possible formulations
| of existing concrete ingredients and pushing out the
| pareto frontier for the best possible concrete that way.
| Also, one probably shouldn't be using bleeding-edge
| concrete tech for a skyscraper foundation - in a safety
| critical application like that you just build it 1.2x
| bigger than you need and it'll still be much cheaper and
| safer than a process like what you just described.
|
| Materials research is super interesting, though, even if
| it's not building up from quantum-particle scale
| research. And atomic / molecular features of inputs can
| yield interesting material candidates.
|
| Source: I work (as a software dev, not a materials
| researcher) at Citrine Informatics, selling software to
| assist companies who are trying to do practical materials
| things like make better concrete.
| marcosdumay wrote:
| Your metaphor simply doesn't reflect the reality.
|
| Material sciences, condensed matter physics, chemistry
| and etc work up from the abstraction layer of "atoms".
| It's a quite well defined and relevant layer. So, until
| that work brings some different configuration1 for atoms,
| they will have no impact at all.
|
| 1 - It doesn't need to be as new elements, but even for
| the resonance between the nucleus and electrosphere they
| didn't create anything new, and only things affecting the
| electrosphere matter. (Even then, they didn't create
| anything new on a nucleus either.)
| peteradio wrote:
| If you wanted to build a skyscraper taking into account
| quantum mechanics then maybe you are hoping to induce a
| scaled quantum mechanic effect? Perhaps in the ultra-modern
| evolution of buildings the structure of the building itself
| will have a communication aspect associated with its
| natural largess and to accomplish this quantum mechanics is
| used to derive the appropriate building structure. Just
| because it sounds far-fetched or hard doesn't mean it won't
| be humdrum engineering decades or a century in the future.
| It all starts somewhere.
| dylan604 wrote:
| > We don't know how far we can push it.
|
| Like all things in science has any stopped to think if we
| should push it?
| bettysdiagnose wrote:
| Yes, certainly, this isn't Jurassic Park.
| dylan604 wrote:
| You reply in jest, but I'm not asking to be funny with a
| movie reference.
|
| We see it day in and day out where science has developed
| something without slowing down to do research into the
| affects other than the one they are scoped in on while
| making what they are making. I'm specifically thinking of
| the new chemical sciences that have brought out some
| formulas that are great at a specific thing, but are
| absolutely tragic to nature in so many more ways. The
| science shows these chemicals to be tragically toxic, yet
| that info gets shoved in a drawer so inventors can make
| money.
|
| Great, we made something, but we should be able to say
| thanks but no thanks. Let's put that in the column of
| good idea, good science tech to achieve, but best left
| alone. Take that learning and try to achieve the
| samething in a different manner so that it doesn't kill
| everything else.
| empi wrote:
| There's a clear difference between discovery/development
| and practical application. The latter is not a problem of
| science.
|
| Shelving discoveries based on the perceived effect they
| (could) have (who would even evaluate that?) is a
| slippery slope if I ever seen one.
| dylan604 wrote:
| >Shelving discoveries based on the perceived effect they
| (could) have (who would even evaluate that?) is a
| slippery slope if I ever seen one.
|
| This is precisely what _should_ happen though. We made
| ICE powered cars that used leaded gasoline because
| reasons, but the results of that were horrible for
| everything except the ICE. We shelved that tech because
| it was just bad.
|
| We've shelved the widespread use of lead in paint. We've
| shelved the widespread use of asbestos in lots of things.
| There's nothing wrong with realizing the juice isn't
| worth the squeeze. We know that it is something that
| happens. Sometimes we make something that comes with a
| heavy cost. Obviously we don't have a way to know that
| until it exists. Then again, we should be able to start
| recognizing that particular chemical chains results in
| bad things so we should be super careful with the new
| thing because it is looks like something we've seen
| before. We can do this with virus and what not. Why not
| with chemistry?
| echelon wrote:
| > There's nothing wrong with realizing the juice isn't
| worth the squeeze.
|
| The LHC employs a lot of people working on smart things.
| CERN gave rise to the world wide web and there are many
| other innovations in computing, construction, and theory
| that come from the work being done there.
|
| > The Large Hadron Collider took about a decade to
| construct, for a total cost of about $4.75 billion. [1]
|
| > Since the opening of Mercedes-Benz Stadium in 2017, the
| Falcons organization has publicly pegged the cost of the
| building at $1.5 billion [2]
|
| It's the same order of magnitude of cost as a sports
| stadium. It's a tiny slice of the worldwide economy.
|
| We don't know where the key discoveries in "theory state
| space" are, so we continue to search. Finding the right
| evidence or surprises could lead to rapid changes in how
| we think and view the universe.
|
| I'm sure some medieval people must have found scientific
| tinkerers wasteful as well.
|
| Diversification of investment is good. It's not like all
| research dollars are going to high energy physics.
|
| [1]
| https://www.forbes.com/sites/alexknapp/2012/07/05/how-
| much-d...
|
| [2] https://www.ajc.com/sports/atlanta-falcons/mercedes-
| benz-sta...
| JackFr wrote:
| > The science shows these chemicals to be tragically
| toxic
|
| I doubt that the science can show a compound to be
| tragically toxic any more than it could show a compound
| to be hilariously toxic, frightenly toxic or delightfully
| toxic.
|
| Apart from an observer, who is typically human (though
| sometimes in our mind an athropomorphized animal or
| superhuman deity) I'm not sure anything in nature can be
| tragic. It just is. No one mourns the trilobites.
| dylan604 wrote:
| You say that, but it _should_ be part of the creating of
| something new. It should be studied to see what negative
| effects it has. We have enough collective knowledge to
| know that even when things are created to do good, some
| negative things sometimes occur. It 's not beyond
| reasonable to have the new thing tested in these negative
| reactions as well.
| optimalsolver wrote:
| Obligatory:
|
| http://dresdencodak.com/2009/09/22/caveman-science-fiction/
| tonymet wrote:
| can someone explain where Cern gets the $50B+ to build and
| operate the LHC? their discoveries have a dubious theoretical and
| practically zero commercial application. there must be a hidden
| weapons / military application to justify a massive money hole
| jamesmaniscalco wrote:
| You are off by a factor of ten [0].
|
| [0] https://home.cern/resources/faqs/facts-and-figures-about-
| lhc
| sampo wrote:
| It's been a tradition for 90 years now.
|
| Since first "high energy" particle accelerator in 1932, we have
| used particle accelerator to smash and study subatomic
| particles. First we found a whole zoo of them, but then 1961
| Gell-Mann's quark model explained how all those subatomic
| particles are not elementary particles, but made of various
| combinations of quarks.
|
| From 1975 we've had the standard model of particle physics, and
| after 2012 with the experimental discovery of the Higgs boson,
| now we've found all the particles in the standard model. But
| the road up to 2012 was: Keep building bigger accelerators,
| keep adding more energy, keep finding new particles. Why stop
| now?
|
| Some skeptics say that now we have maybe found them all. And we
| don't have a good theory that would predict new particles, so
| maybe we won't find new elementary particles, no matter how we
| go on. Maybe we should pause and reconsider. Work on new
| theories.
|
| But, we also have theories: Supersymmetry, and string theory.
| Supersymmetry predicts the existence of the superpartners of
| all the 17 elementary particles. Maybe their discovery is just
| behind the corner, if we just keep going? Or maybe
| supersymmetry is wrong, and the superpartners don't exist at
| all.
|
| Timeline of discoveries of the elementary particles:
| 1800-1895 photon 1897 electron 1937 muon
| 1956 electron neutrino 1962 muon neutrino 1969
| down quark 1969 strange quark 1969 up quark
| 1974 charm quark 1975 tau 1977 bottom quark
| 1979 gluon 1983 W boson 1983 Z boson
| 1995 top quark 2000 tau neutrino 2012 higgs
| pbhjpbhj wrote:
| Discovers? Or invents? I've only studied particle physics at
| undergrad level but strikes me that these tetraquarks and
| pentaquarks could be combinations never created by any [other]
| natural process.
| davrosthedalek wrote:
| There are cosmic rays of almost arbitrary energy, collisions
| like the ones at LHC are happening all the time in the
| universe. So surely these particles will have been created
| before somewhere else.
| [deleted]
| tsimionescu wrote:
| By my understanding, the LHC isn't doing anything different
| from what's happening in the upper atmosphere every
| microsecond, when solar rays are hitting the Earth; except that
| the LHC is much lower energy than some of those collisions.
| easygenes wrote:
| Yep, there's a class of thing called UHECR (Ultra-High Energy
| Cosmic Rays). We still have barely a clue what generates
| them, but they hit our atmosphere with roughly ten million
| times the energy of what LHC can muster.
| lumost wrote:
| Isn't it more accurate to say we don't know their primary
| sources? It's extremely likely that the are generated in
| stellar processes and black hole ejects, no?
| semi-extrinsic wrote:
| I mean, saying something in the universe is generated in
| a stellar process is borderline tautological, no? We are
| all stardust and we derive all our energy from the sun,
| after all.
| shagie wrote:
| Kind of... maybe... there are some interesting problems
| with various sources.
|
| First, not sure about the process that generates them.
| Saying "they came from an active galactic nuclei is ok...
| but _how_ did they get accelerated to such energies?
|
| The next problem is that being so highly energetic, they
| should be interacting with the cosmic background
| radiation if they're traveling about 160 mLy which would
| drain off some energy (
| https://en.wikipedia.org/wiki/Greisen-Zatsepin-
| Kuzmin_limit ) and there are some observations that
| appear in violation of that limit (
| https://en.wikipedia.org/wiki/Oh-My-God_particle )
|
| https://www.quantamagazine.org/cosmic-map-of-ultrahigh-
| energ... is also interesting to look at (very neat
| visualization).
|
| Part of the problem is that we're not entirely sure what
| they're made of. Most theories have been working on the
| "they're protons" assumption, but other approaches with
| having them be heavier nuclei means that they don't need
| to travel as fast to have the same amount of energy
| (which also changes the equation for the GZK limit as
| that applies to protons).
| lumost wrote:
| Thanks this makes sense, My underlying assumption was
| that a typical star has magnetic acceleration paths which
| have many orders of magnitude more energy than the LHC
| (Many intentionally used ambiguously as I have not done
| the math).
|
| I suppose given the energies involved, we would need to
| observationally ascertain where in the sky the cosmic
| rays come from in order to put bounds on how they were
| made and what they are made of.
|
| Do yo know of any efforts to observe cosmic ray sources
| or build a cosmic ray telescope?
| shagie wrote:
| > ... we would need to observationally ascertain where in
| the sky the cosmic rays come from in order to put bounds
| on how they were made and what they are made of.
|
| This is part of the challenge - the map of where they are
| hint at some hot spots (
| https://skyandtelescope.org/astronomy-news/cosmic-rays-
| hint-... ) but as these are charged particles (not light)
| the path that they follow isn't necessarily a "draw a
| straight like back to the source"
|
| > Do yo know of any efforts to observe cosmic ray sources
| or build a cosmic ray telescope?
|
| We don't directly observe the cosmic rays, but rather the
| cascade of particles that they make as they crash through
| the atmosphere.
|
| There are several different approaches to this.
| https://en.wikipedia.org/wiki/Cosmic-ray_observatory
|
| For example, there's Ice Cube ( https://en.wikipedia.org/
| wiki/IceCube_Neutrino_Observatory ) and a visualization
| of some of its results - https://youtu.be/2DDQYHIbL3Q and
| https://youtu.be/rSwbL2coz_Y
|
| Another cosmic ray observatory - https://www.auger.org //
| https://en.wikipedia.org/wiki/Pierre_Auger_Observatory
|
| > But since these high energy particles have an estimated
| arrival rate of just 1 per km2 per century, the Auger
| Observatory has created a detection area of 3,000 km2
| (1,200 sq mi)--the size of Rhode Island, or Luxembourg--
| in order to record a large number of these events. It is
| located in the western Mendoza Province, Argentina, near
| the Andes.
|
| Pierre Auger is looking at air showers -
| https://en.wikipedia.org/wiki/Air_shower_(physics)
|
| ---
|
| I'd also suggest checking out PBS Space Time (in general)
| and in particular this episode - The Oh My God Particle -
| https://youtu.be/osvOr5wbkUw
| jug wrote:
| Could it simply be far travelled gamma-ray bursts? Not sure
| how it works, if tiny bits of them towards Earth can
| survive very far, without far less likely extinction
| events. Just trying to think of extremely energetic
| sources...
|
| Of course, we aren't entirely sure of what GRB's come from
| _either_ :D
| metalliqaz wrote:
| no they aren't gamma rays
| jug wrote:
| I have to keep reminding me of this! We're here down on Earth
| looking for ways to push science further and reconcile the
| quantum world with the Standard Model, while the atmosphere
| may already produce things like gravitons or some exotic
| version of Supersymmetry that demands higher energies than
| expected.
| turbinerneiter wrote:
| So we just need to lift the measurement equipment into the
| upper atmosphere and wait :D
| snowwrestler wrote:
| You joke, but before powerful particle accelerators,
| physicists really did just lift detectors higher into the
| atmosphere--either on planes or by carrying them up very
| tall mountains.
| turbinerneiter wrote:
| I know of some high altitude balloon and satellite
| experiments as well. I guess size and weight are a
| limiting factor to what one can detect with those.
| FredPret wrote:
| So we should build the Even Larger Hadron Collider? (I vote
| yes to use my tax dollars for this)
| ars wrote:
| It's not exactly the same - the energy of solar rays is
| higher, but the residual momentum is a problem. Most of the
| available energy is needed to conserve momentum in the final
| product, unlike the LHC which collides two particles moving
| in opposite directions, leaving all kinetic energy available.
| ufmace wrote:
| Yup. The main advantage of the LHC is that they're happening
| right in the middle of a giant sophisticated detector and at
| known energy and timing.
| peteradio wrote:
| LHCb != LHC
|
| LHCb refers to the specific detector and group responsible for
| measurements related to b-quark.
| ChrisArchitect wrote:
| Space marketing is tough as it is with space station updates,
| rovers, Mars etc from NASA et al, but this is just a whole other
| struggle. Is the general public supposed to care about the LHC
| starting up again etc? Higgs Boson was a total 'meh' moment ten
| years ago after a bit of hype. I suppose particle physics etc is
| just too obscure.
| immmmmm wrote:
| composite particles: quarks and gluons in weird configuration :)
|
| still the desert otherwise, a higgs and nothing else :(
| OseArp wrote:
| It may need clarifying that "exotic hadron" simply and
| specifically means "hadron with more than three quarks." What's
| being reproted is finding new particles belonging to a family
| that already has several known members.
|
| https://en.wikipedia.org/wiki/Exotic_hadron
___________________________________________________________________
(page generated 2022-07-05 23:00 UTC)