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posted by janrinok on Monday September 30 2019, @09:48AM   Printer-friendly
from the Higgsldy-Piggsldy-my-dark-boson,-she-makes-matter-for-everyone dept.

Space reports on a potential solution to the baryon asymmetry problem (why the ratio of matter to antimatter in our universe is ~1 billion to 1).

The puzzler is that in almost all interactions, matter and antimatter are created in equal proportion. It is apparently a fundamental symmetry of the universe. Yet,

Somehow, when the universe was incredibly young, almost all the antimatter disappeared, leaving just the normal stuff. Theorists have long stalked the ever-elusive explanation — and more important, a way to test that explanation with experiments.

Three physicists from Brookhaven National Laboratory in New York and the University of Kansas have proposed a new theory, published in arXiv, that details a possible solution involving three Higgs Bosons. One of these is the Higgs we know at 125GeV with two proposed new ones in the 1 TeV neighborhood.

The two new Higgs decay into showers of particles at slightly different rates and with slightly different preferences for matter over antimatter. These differences build up over time, and when the electroweak force splits up, there's enough of a difference in matter-antimatter particle populations "built in" to the universe that normal matter ends up dominating over antimatter.

The abstract of the paper notes that the prediction "is in principle a testable model." This testing may have to wait for another generation of colliders however.

It is also worth noting that 1000GeV appears to be at least in part a prediction of convenience to facilitate testing, the theory could be reworked for higher values, but "There's no use predicting the existence of a particle that can never be detected."

 


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  • (Score: 2) by Immerman on Monday September 30 2019, @02:01PM (6 children)

    by Immerman (3985) on Monday September 30 2019, @02:01PM (#900791)

    And what's the mechanism by which antimatter was preferentially sucked in, while the matter created at the same spot was not?

    Without a suggested mechanism, it's all just idle speculation. Within current theory there's no reason to expect either to be dominant - everything should have just kept cycling between matter and energy forever.

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  • (Score: 0) by Anonymous Coward on Monday September 30 2019, @05:23PM (5 children)

    by Anonymous Coward on Monday September 30 2019, @05:23PM (#900867)

    Imagine billions of matter-antimatter pairs popping into existence with most annihilating each other but a few appearing right at the event horizon so that one of the pair gets sucked in before they can annihilate. What mechanism would ensure this occurred at exactly equal rates for matter and antimatter (not on average, but exactly even all the time)?

    All you need is a tiny imbalance that would then grow until one type of matter dominated. That should be the default hypothesis. The situation with equal amounts is not stable except in a homogeneous universe (which we do not live in).

    • (Score: 2) by Immerman on Monday September 30 2019, @05:44PM (4 children)

      by Immerman (3985) on Monday September 30 2019, @05:44PM (#900878)

      The imbalance woudn't "grow until one type of matter dominated" unless there was some mechanism that was preferentially pulling one type of matter into the kugelblitz. Otherwise it's just a random buildup that's going to be very close to balanced. Like flipping coins - you can get a significant imbalance at low numbers, but if the odds of getting heads are exactly 50%, then as the number of coin flips approaches infinity the balance approaches the statistical ideal.

      You're also assuming that the entire universe was at the boundary of this singularity during the formation of matter - but at that point the universe had likely already doubled in size something like 100 times in a tiny fraction of a second (the inflationary "bang" of the big bang) - there was no longer any causal linkages between different parts of the universe, so even if you had some sort of singularity gobbling antimatter in one corner, the rest of the universe would be unaffected.

      A chance imbalance with a singularity also assumes that there was vastly more material in the early universe than there is now, since it would have gobbled up most of the matter along with all the antimatter - and all that's left now is an infinitesimal fraction of what originally existed... which I think would drastically rewrite pretty much everything we think we know about the early stages of the universe. In contrast, a similarly slight imbalance in the decay path from energy to matter would leave 100% of the original material present, with all the antimatter converted into matter as mass-energy cycles from energy to matter and antimatter, which annihilate back into energy except for the slight excess of matter, and the cycle just keeps repeating until only matter is left. At the insane energy densities of the early universe that could happen *very* fast.

      • (Score: 0) by Anonymous Coward on Monday September 30 2019, @06:04PM

        by Anonymous Coward on Monday September 30 2019, @06:04PM (#900891)

        The imbalance woudn't "grow until one type of matter dominated" unless there was some mechanism that was preferentially pulling one type of matter into the kugelblitz

        Imagine you have 1 proton and 0 antiprotons. Then there is a 50/50 chance the next particle is a proton, in which case you have two protons. otherwise you are back to 0 protons and zero antiprotons. Then you would start over... you eventually get 1 proton and 0 antiprotons (or vice versa, "proton" just means the type that comes first). So you eventually get 2 protons, then if the next is an antiproton you are left with 1 proton and zero antiprotons... etc. Whichever type came first will preferentially grow because all the later anti-particles are going to get annihilated, while the particles do not.

      • (Score: 1, Informative) by Anonymous Coward on Monday September 30 2019, @06:31PM (2 children)

        by Anonymous Coward on Monday September 30 2019, @06:31PM (#900905)

        Here is a simulation in R. You can see starting from zero particles with equal odds... one of the types will eventually dominate:

        n_steps = 1e6
        res     = matrix(ncol = 2, nrow = n_steps)

        n0 = n1 = 0
        for(i in 1:n_steps){
          x = sample(0:1, 1)

          if(x == 0){
            if(n1 > 0){
              n1 = n1 - 1
            }else{
              n0 = n0 + 1
            }
          }

          if(x == 1){
            if(n0 > 0){
              n0 = n0 - 1
            }else{
              n1 = n1 + 1
            }
          }

          res[i, ] = c(n0, n1)
          if(i %% 1000 == 0){
            plot(res[1:i, 1], ylim = range(res[1:i, ]), type = "l", lwd = 3, panel.first = grid())
            lines(res[1:i, 2], col = "Red", lwd = 3)
          }
        }

        They trade off for awhile but eventually it just becomes too unlikely to get an anti-particle dense sequence so that the anti-particles to annihilate all the existing particles and begin accumulating instead. If you left it running long enough you will see it switch again though... but the point is there will be long periods where one type of particle dominates.

        I left it going but took a screenshot after about 200k steps: https://i.ibb.co/G9bVzRp/kugel.png [i.ibb.co]

        • (Score: 2) by PartTimeZombie on Monday September 30 2019, @08:51PM (1 child)

          by PartTimeZombie (4827) on Monday September 30 2019, @08:51PM (#900984)

          That is very interesting, thanks for that.

          I'm pretty sure the Universe is written in C though.

          • (Score: 0) by Anonymous Coward on Monday September 30 2019, @09:12PM

            by Anonymous Coward on Monday September 30 2019, @09:12PM (#900992)

            I doubt you could create such a concise script including live plotting, etc in C.