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Science

Large Hadron Collider Discovers Three New Exotic Particles (home.cern) 91

The international LHCb collaboration at the Large Hadron Collider (LHC) has observed three never-before-seen particles: a new kind of "pentaquark" and the first-ever pair of "tetraquarks," which includes a new type of tetraquark. The findings, presented today at a CERN seminar, add three new exotic members to the growing list of new hadrons found at the LHC. They will help physicists better understand how quarks bind together into these composite particles. From a report: Quarks are elementary particles and come in six flavours: up, down, charm, strange, top and bottom. They usually combine together in groups of twos and threes to form hadrons such as the protons and neutrons that make up atomic nuclei. More rarely, however, they can also combine into four-quark and five-quark particles, or "tetraquarks" and "pentaquarks." These exotic hadrons were predicted by theorists at the same time as conventional hadrons, about six decades ago, but only relatively recently, in the past 20 years, have they been observed by LHCb and other experiments.

Most of the exotic hadrons discovered in the past two decades are tetraquarks or pentaquarks containing a charm quark and a charm antiquark, with the remaining two or three quarks being an up, down or strange quark or their antiquarks. But in the past two years, LHCb has discovered different kinds of exotic hadrons. Two years ago, the collaboration discovered a tetraquark made up of two charm quarks and two charm antiquarks, and two "open-charm" tetraquarks consisting of a charm antiquark, an up quark, a down quark and a strange antiquark. And last year it found the first-ever instance of a "double open-charm" tetraquark with two charm quarks and an up and a down antiquark. Open charm means that the particle contains a charm quark without an equivalent antiquark.

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Large Hadron Collider Discovers Three New Exotic Particles

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  • They keep finding these bloody things. Where will it end?
    • by Entrope ( 68843 )

      There used to be 108 of them, but demand was so high that they had to invent more in order to cash in on that large-particle-collider profit machine. Depending on who you ask, there may be anywhere between 418 and 913 so far.

      Gotta catch 'em all!

      • Back in my day, there was only 152 pokemans and we liked it that way.
    • Rather than "types" of things, it sounds more like combinations of something still not understood. It's kind of like "elements" before the atomic model was devised: they all seemed like multitudes of "dedicated" substances, when in fact they were merely combinations of electrons, protons, neutrons, and croutons. (Okay, I added the last because I'm hungry.)

      I'll propose these quark-ish things are all made of 3 types of undiscovered Dark Specks.

      • by Sique ( 173459 )
        That's exactly what this article is about: combinations of four and five quarks. Neutrons and protons have three of them, mesons two. You can imagine the new particles as kind of proton-meson or meson-meson combinations.
      • by HiThere ( 15173 )

        It's not even that. These are things with really short half-lives. It's sort of like the unstable transition stages in a chemical reaction, only much faster, and on a much smaller scale.

        And again, just like chemistry, it might be really useful to be able to predict how those transition stages worked. But it also might not And you can't tell ahead of time.

    • If it quarks like a duck, then maybe it is a duck. There may well be an infinite number of different quark particles. So yet another quark would just roll off my back like a duck.
    • Never?

      e=mc2 tells us that energy and mass are the same things. Particles are waves and we know that there can be an infinite variation of waves (think music), a few of which can be the stable quantum standing waves we call particles.

      Their existence provides empirical evidence to verify the mathematical models we use to describe reality which is the core purpose of physics.
  • TFS suggest they were predicted by theory but never observed before. So the title is misleading?
    It would be interesting if these were truly new - not predicted by the theories.

  • by LordHighExecutioner ( 4245243 ) on Tuesday July 05, 2022 @09:41AM (#62674684)
    ...but just new combinations of the old ones. If they had discovered a particle not predicted by the Standard Model, that would be very interesting!!!
    • by jd ( 1658 )

      Yes, it's true they're not fundamental particles, but they're still considered particles. What matters is that their energies and lifespans place additional constraints on the strength and behaviour of the strong nuclear force (the only nuclear force not adequately combined with the others, the model for the electro-weak force being now on pretty solid ground). If they can pin the strong nuclear force down sufficiently to merge with electro-weak, they'll have the Unified Theory they've been after for a whil

  • How can quarks and antiquarks exist in the same particle? Can atoms have electrons and positrons in them? I think physics should change its terminology because anti particles are not exactly antimatter. Anti particles can only annihilate their specific opposites. Anti particles do not have negative gravity. Anti particles have the same strong and weak force interactions that normal particles have. The only way positrons seem to differ from electrons is charge, and why does that cause them to annihilat
    • by Tablizer ( 95088 )

      > change its terminology because anti particles are not exactly antimatter.

      "Misunderstood matter"?

      > Anti particles do not have negative gravity.

      Nothing may have negative gravity, as it may not be a "force" like the other 3. Nobody really knows, gravity is still a great mystery. It would be nice if there were such a thing because then we could have flying cars that don't wake up the entire town.

      • Gravity doesnâ(TM)t actually exist as a force if it really is a manifestation of bent space.
        • That is correct. It's a fictional force if its nature is indeed as GR claims (even if GR is problematic at high energies).

          From a purely theoretical perspective, however, something with negative energy would have negative "gravity" (ignoring all of the massive fucking problems that exist if that is really possible)
          • by Tablizer ( 95088 )

            If gravity is just "bent space/time" how could something ever "fall up" using gravity alone? Other than maybe it can "fiddle with" time?

            • Other than maybe it can "fiddle with" time?

              That's GR in a nutshell.
              Diverging four-vectors through spacetime (which have longer proper distances than are visible in 3d space) are responsible for what we see as attraction (or repulsion in the case of a negative stress-energy tensor). This is why time dilates in a gravity well. "Space" is smaller and "Time" is longer (those 2 being intimately linked).

              I.e., gravity is the distortion of (space)time.

              In the case of a positive stress-energy tensor, the curvature of space (as projected in 3d space- but

    • by gtall ( 79522 )

      " it is just a unique kind of matter particle that happens to annihilate a specific kind of similar particle and has an opposite charge"

      Hence the term "antimatter". What the hell difference would it make if they called it them, say, Oppositely Concerned Paired Molides.

    • by sjames ( 1099 )

      Quarks and anti-quarks can form as virtual particle pairs and can mutually annihilate in some configurations.

  • quarks are made of stuff too. Smaller stuff I'm sure. And that stuff is also made of stuff and... so on.
    • by Tablizer ( 95088 )

      It's fractal recursive turtles all the way down to the fractal recursive turtles.

    • by sjames ( 1099 )

      Quite possibly not, or possibly not in a way we will be able to observe.

    • by jd ( 1658 )

      If quarks are made of anything, it's likely to be either superstrings or pure mathematics. We can't build an accelerator to split something into strings, although it's just possible that the energies in space are sufficiently high that we can see strings if we built a detector there. However, we can potentially detect supersymmetry particles and these necessitate superstrings, although we really want the long-promised 100 mile accelerator to be sure of finding those.

      Again, building a detector in space stand

      • Quantum Field Theory describes how all particles are generated from the various fields that exist across the entire universe. It is "theory" in every common usage of that word, but utterly fascinating just the same: https://youtu.be/zNVQfWC_evg [youtu.be] (1h 18s of David Tong at RI describing QFT for laypersons).

        Fun Fact: Did you know that the force carrier for some of these subatomic particles is the photon? That means that you're being held together by light!
    • That would be the end of the standard model.

      Not saying it's impossible, but I'm not going to bet on it happening.
      Composite leptons pose all kinds of problems that we should have encountered by now. Pair production statistics and muon/electron annihilation would be all wrong.

      So no, quarks likely aren't made of stuff too.
      • The observable universe is most likely not the whole story, and since we can only observe such a tiny amount I doubt we will ever have a full understanding of the cosmos before we self destruct.
        • Oh, I agree entirely with you on that regard.

          I'm just saying that, as far as we can measure the observable Universe, it's highly unlikely we'll ever find muons to be composite particles within that limited framework.
          That's string theory stuff- which hell, could ultimately end up being right. But the standard model is what it is, because it works as the universe is observed. Any speculation that directly breaks it is unlikely to be true in any way we can ever measure.
  • By the end of the summary I was laughing out loud at how totally stupid the article made me feel!

    Unless you are in the field, how can you read the following and not feel absolutely worthless?

    Two years ago, the collaboration discovered a tetraquark made up of two charm quarks and two charm antiquarks, and two "open-charm" tetraquarks consisting of a charm antiquark, an up quark, a down quark and a strange antiquark. And last year it found the first-ever instance of a "double open-charm" tetraquark wit
    • by GoTeam ( 5042081 )
      Shit, I read everything wrong. I thought a quark was a type of NFT. If I can't crypto-NFT anything from this article, then it isn't science and doesn't belong on Slashdot!
    • If you cannot grok a quark then you need to hand your geek card back.
    • by nebaz ( 453974 )

      Been a while, but I basically remember quarks being the basic building blocks of protons and neutrons. 6 types of quarks:
      top, bottom, strange, charm, up, down. (Not sure why up and down AND top and bottom). But the above just describes some new particles made up of these things. I guess there are antiquarks too. If I recall correctly, protons and neutrons contain 3 quarks generally.

      This is just saying there are some particles that contain 4 or 5 quarks. I don't think it's too hard to parse the sentenc

  • What's so special about charm, and why is an open-charm tetraquark more significant than an open-bottom tetraquark for instance?

    On another note, I just learned charm and bottom are the heaviest types of quark. Other quarks decay to lighter quarks, eventually into charm and bottom. I made up a mnemonic device about "bottom" and "charm" but I'm not going to share it.

    • by Mal-2 ( 675116 )

      I hope your mnemonic doesn't break too hilariously when you substitute "truth" for "top" and "beauty" for "bottom", as some sources do. They're the same quarks, but only the initial is actually a standard. The rest of the name is convention, and there happen to be two conventions.

    • by ceoyoyo ( 59147 )

      You might want to reconsider your mnemonic. The top and bottom quarks are the heaviest. Quarks can decay in various ways, but often end up as the lightest ones: the up and down.

      • by piojo ( 995934 )

        Ugh, thank you for the correction, and I'm not sure how I got that so completely wrong. Obviously conservation of energy says a particle can't decay to a heavier particle. I must have been too mentally occupied trying to imagine what it really meant for particles to be so perfectly opposite that they become pure energy upon contact (intentionally not thinking of them as waves).

        • by ceoyoyo ( 59147 )

          Well, if it makes you feel better, they're just creating a system with zero net conserved quantities (charge being the main one) so they can decay into photons.

          If it makes you feel even better, all the particles concerned are just energy to start with.

  • The truth is that they are finding precious little of any relevance, and nothing at all of what would make a big difference - like e.g. supersymmetric partners, without which string theory is far, far less compelling. But, they have to get the hype machine going in top gear in order to drum up support for LHC's successor, with a multi-billion dollar price tag that could instead be devoted to much more promising projects in the physical sciences.

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