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Matter, Anti-Matter, and a New Subatomic Particle?
sciencehabit writes "Physicists may have finally figured out why the universe contains more matter than antimatter. The key lies in a flaw in the relationship between the two and a potentially new subatomic particle. 'Other researchers, however, say the results, published today in Nature, should be interpreted cautiously. It could all be an effect produced by run-of-the-mill particles'."
Anyone remember the particle-of-the-week on Star Trek? Yeah. Modern physics feels like that sometimes.
Where does dark matter fit into that cosmological view?
A flaw in our understanding of it. Quit making flames for the sake of making flames because there is no basis in the article for what you said. You'll look less stupid in the process.
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So did Garrett Lisi predict the new particles? Do they fit into the E8 algebra thing that his theory is based on?
Without this "flaw" matter and anti-matter would have cancelled out almost perfectly early on in the Big Bang leaving nowhere near enough matter (or anti-matter) to form galaxies or stars. So this "flaw" is what allows us to exist. I would not call it a flaw, but rather a design feature. Without breaking this symmetry the Universe would be a really boring place, in much the same way that a tree is more interesting than a cube even though the cube has far more symmetry.
All this paper shows is that there is a difference between CP violation in the charged B mesons and the neutral B mesons. This is somewhat unexpected and while you cannot rule out something new it is also true that they cannot rule out QCD (strong force) effects.
The problem the strong force is that it is so strong at low energy that our normal technique to calculate what is going on (called perturbation theory) does not work because, rather than small perturbations, the strong interaction causes huge changes. This means that theorists have to make approximations in order to calculate anything and so their results may well just show a flaw in their assumptions rather than a flaw in our understanding of physics.
An excellent example of this was with my grad student experiment which was also measuring CP violation but with kaons. Before our measurement the theorists were saying that there was absolutely no way at all they could have a certain parameter (epsilon'/epsilon) to have a value greater than 1e-3 and it would likely be a lot lower. So, we measured it at around 1.7e-3 and, lo and behold, the theorists adjusted their models and suddenly it was in agreement with theory.
So while this might be an indication of something new I am not yet convinces that it is anything more than an incorrect assumption in a QCD calculation somewhere. Such calculations are fantastically difficult and while in this case there are things that will make it easier, it is not yet convincing evidence.
Baryons are hadrons (particles composed by quarks), specifically three quarks, and the proton and neutron are the lightest and most stable of baryons.
The Baryogenesis theory, as proposed by Sakharov, describes a set of three conditions which all had to be met together in order to have a matter-asymetric universe. A baryogenic reaction sets off from a baryon-symmetric state to produce a final state which has a greater content of particles than anti-particles; or, in effect, no anti-particles and a "small" ammount of matter particles (in comparison to the number of annihilation photon "sea" which might be interpreted as the Cosmic Background Radiation). According to Sakharov, a potencially baryogenic reaction has to satisfy all of three conditions:
- It must violate the baryonic number, i.e., the number of baryons in the final state must differ from the initial state. This might seem a trivial requirement, but under the current (very successful) Standard Model of Particle Physics, it is not.
- It must violate CP (charge-parity) symmetry. In other words, the physics of the reaction/decay must be different from its charge-conjugated (and parity-conjugated) counterpart. Specifically, the rate of a baryogenic reaction must differ from the reaction involving the corresponding anti-particles, due to a non-trivial theoretical result known as "CPT theorem".
- It must happen away from equilibrium (thermal and "chemical"). In other words, the reaction rate must be faster than the time it takes for the mixture between initial and final state domain contents to mix and reach equilibrium.
The first two conditions are mostly related to particle physics, and the third is more oriented to cosmology and especially the macroscopic treatment of the universe with (relativistic) thermodynamics. IMHO, the trickiest is to find a decay that satisfies the first condition, since in the Standard Model of Particle Physics this should not happen directly (technically, the baryon number operator does not show up explicitly in the Standard Model Hamiltonian).From what I've gathered, this is the job of looking for a "new" particle whose decay can, not only, satisfy the three Sakharov conditions, but also give the correct predictions. The matter-to-radiation content is fairly precise: it's very small, but not null, about 1 matter particle (think "hydrogen atom") per 10 billion (1010) cosmic background radiation photons. It's one thing to find a particle whose decay satisfies the Sakharov conditions, especially one that violates the baryon number conservation "directly" (i.e., as a "first order" process); it's another thing entirely to justify that that same decay is enough to give that particle-to-photon ratio within an order of magnitude.
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