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Science

Antimatter Decay Rates Explain Existence Of Matter 9

Paintthemoon writes: "The Stanford Linear Accelerator Center released a paper Friday that may explain why matter won the battle with antimatter following the big bang. In studies of B mesons, they determined that there is a significant differential in decay rates between B mesons and anti-B mesons. Similar studies in the 60s of K mesons led to a Nobel Prize."
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Antimatter Decay Rates Explain Existance Of Matter

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  • by Kris_J ( 10111 ) on Saturday July 07, 2001 @05:18PM (#101393) Homepage Journal
    What this says to me is that there is something smaller than the B meson and that the "positive" version is (now) much more prevalent than the "anti" version, such that anti-B mesons get annihilated in the sub-sub-atomic version of a matter-antimatter reaction faster than the B meson.

    That is to say that this is a symptom, not a cause.

    --

  • if in fourteen billion years, the amount of antimatter in the universe has decayed to such a minimal level, then in fourteen billion more years, will the level of regular matter be at a similarily small level?

    The nearly nonexistent level of antimatter in the modern universe is not the result of decay, but of annihilation: matter meets antimatter, and poof! The problem is that there should then be no matter in the universe, either (it would have gone poof with the antimatter). We can explain this by either saying that they are produced at unequal rates (if we begin with more matter than antimatter, we will be left with more matter after the reactions have taken place) or by saying that one decays more quickly than the other: they would be produced at equal rates (which is what we'd expect anyway), but one decays before it has an opportunity to interact with the other, producing the same result.

    So, as another poster has pointed out, we are in no foreseeable danger of decaying out of existence (at the subatomic level). This result doesn't change that, but suggests why we've made it this far at all.

  • This is unlikely, because protons apparently don't decay . I've heard other places that the estimated half-life for protons is longer than the age of the universe, and expected to be longer than the total lifespan of the universe.

    These two statements say essentially the same thing; we have not observed protons decaying. Your link cites an experiment which determined that, if protons do decay, it would be about 10^33 years before it happened to a given proton; this does not mean that protons do not decay, but only that, if they do, they would take much longer to do so than is predicted by the simplest Grand Unified Theory. Thus, regardless of whether protons decay or not, that GUT is incorrect in its prediction.

  • by pubudu ( 67714 ) on Saturday July 07, 2001 @06:50PM (#101396)
    What this says to me is that there is something smaller than the B meson and that the "positive" version is (now) much more prevalent than the "anti" version, such that anti-B mesons get annihilated in the sub-sub-atomic version of a matter-antimatter reaction faster than the B meson.

    The experiment deals with decay, not annihilation. The B meson is made up of smaller particles, viz. a bottom quark and some other anti-quark (up, down, or strange); the B- meson is made up of an anti-bottom quark and some other quark. The other quarks (u, u-, d, d-, s, s-) are more stable than the bottom quarks; therefore, the decay of B and B- mesons is most likely caused by the decay of b and b- quarks (into charm and c- quarks). Seeing that B- mesons decay more quickly than B mesons, we infer that the b- quarks decay into c- quarks more quickly than b quarks decay into c quarks. That is, in this instance (as in the case of K mesons), the antimatter particle decays more rapidly than its matter counterpart. (We can't measure the decay rates of b and b- quarks directly because quarks are only observable in color-neutral particles, so we must observe these particles in their decay to determine the decay of these quarks.)

    But as the experiment deals with decay, and not annihilation, the prevelance of one (matter/antimatter) over the other does not explain the results.

    btw, here's [aip.org] a non-MSNBC article that deals with the issue. Here's [rl.ac.uk] a page that discusses the decay of b quarks in Bs (bottom-strange combination) mesons.

  • That is to say that this is a symptom, not a cause
    You're right, but that's not the point. This experiment is really a kind of double negative rather than a positive.

    What I mean is this: there are many models that might explain why there is more matter than antimatter. However they generally presuppose a difference between matter and antimatter and so if such differences are not observed we can reject these models out of hand. What an experiment like this does is make us even more sure that there is a difference between matter and antimatter meaning that all those models that we previously rejected are now open for business again.

    Ie. this experiment contradicts a proposition that could have been used to counter certain explanations of the matter-antimatter imbalance.

    It's not necessarily the B-mesons themselves that are interesting.

    --
  • I've heard of K mesons, Mu mesons, and Pi mesons (and proud to say: I even had some of that stuff on a test once). But I have never heard of B mesons. I am not made out of B mesons. I am made out of protons, neutrons, and electrons (so the tribal shamans tell me). I don't even think that B mesons are on the INGREDIENTS list for any of the stuff I am made of.

    So what's the big deal?

    How does this B meson stuff affect me, or anything I can even detect?

    By the way: the big bang never happenned. Check out the book by that title for a popularization of Hans Alfven's steady state hypothesis. Microwave backgounds, and Hubble redshifts are neat, but circumstantial, and dont really prove anything. Alfven (rip) has done some crazy cool work and is worth a look. UFO enthusiasts are not invited....
  • if in fourteen billion years, the amount of antimatter in the universe has decayed to such a minimal level, then in fourteen billion more years, will the level of regular matter be at a similarily small level?
  • I don't even know what a meson is

    I probably have this horribly wrong, please correct me.

    does it mean regular matter is (over time) longer lasting and therefore stronger than antimatter?

  • This is unlikely, because protons apparently don't decay [bu.edu]. I've heard other places that the estimated half-life for protons is longer than the age of the universe, and expected to be longer than the total lifespan of the universe. Physics majors please correct me.

Reality must take precedence over public relations, for Mother Nature cannot be fooled. -- R.P. Feynman

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