An Exciting Asymmetry?

[Update: See the later post entitled “CDF Says No“.]

A big mystery in physics is why there is more matter than anti-matter. (Of course, which we call the matter and which we call the “anti-matter” is a… matter of convention. Take your pick.) It is hoped that there is some mechanism in the laws of physics (at a very basic level concerning particle interactions) that will become apparent that explains it. It’s also hoped that the mechanism itself might have some understandable origin too. The mechanism would operate in the first tiny fractions of a second of the universe’s life when the primordial soup of particles and antiparticles (created from, roughly speaking, the energy of the big bang) began to cool down as the universe expanded. Rather than them annihilating all back into energy again, the mechanism would create an imbalance between the two, giving rise to a matter-filled universe, from which we emerged. So what could be the mechanism, can we isolate it in our theories and in our experiments? Build a good model of it? Explain it?

This is all very first and foremost in people’s minds when there’s a new experiment switched on that is probing the unknown – the Large Hadron Collider. Well, actually, it has been recently announced that a suitable mechanism (or, more precisely, its effects) has been seen in action at the Tevatron experiment at Fermilab in Illinios. There are new strong signals of large CP violating (the technical term for the kind of imbalance that is sought) processes in B-meson systems. Mesons are particles made of pairs of quarks (B-mesons involve b-quarks), and they decay after being made in the collisions at the Tevatron collider, the products of the decay being studied closely in the detectors. It is in looking at these decays that something significant seems to be showing up, as announced by the D0 collaboration. It is not that CP violation has not been seen before (there’s even a Nobel prize for it). It is the amount needed to explain the world around us that’s the issue. The little bit that is known to happen is simply not enough to give the amount of matter that we see. This is news of a large effect, possibly large enough to generate the imbalance in the early universe.

It’s all very exciting if it is confirmed, and we’ll all be looking to other experiments (and especially the LHC) to perhaps give more insight into the physics that’s going on. This is perhaps just the beginning of a gold-rush in the physics, no doubt beginning with everyone trying to see how to incorporate the new effects in their favourite models, and/or constructing new models to reproduce them. As Jester says in a recent blog post:

in the coming weeks theorists will derive this operator using extra dimensions, little Higgs, fat Higgs, unhiggs, supersymmetry, bricks, golf balls, and old tires.

You can read, for example, Jester’s post and Dennis Overbye’s New York Times article* for more on all this. (Don’t miss Joe Lykken’s quote at the end of the latter!)

-cvj

* Thanks Shelley!

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7 Responses to An Exciting Asymmetry?

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  3. Quaoar says:

    It is possible that this experiment is biased by the very fact that it is being observed in a “matter” universe?

  4. TR says:

    How are we able to tell how big the asymmetry must have been to account for our universe? Even if there is only a 1E-10000000 chance of any given particle/antiparticle not having annihilated each other, isn’t it possible that the Big Bang simply produced 1E+10000000 more matter than current contents of the universe?

    BTW – Cool question Quaoar!

  5. Clifford says:

    Quaoar – Not sure I understand the question. As I say at the top, what is called matter vs anti-matter is a convention. If that’s not what you’re asking then I guess you’re asking about whether the experiment depends on being in this universe in some deeper sense and the answer is yes. But why should it not be that way? We are asking a question that pertains to this universe (that has meaning in this universe) and so it is entirely natural that the means we use to address the question are also of this universe too. Context is important.

    Best,

    -cvj

  6. Clifford says:

    TR – We know how much matter there is (or, if you prefer, how much anti-matter there isn’t), so we know how much asymmetry we need.

    You also ask: “isn’t it possible that the Big Bang simply produced 1E+10000000 more matter than current contents of the universe?”

    Well, that’s the point. How did it do that? It needs an asymmetry. We want to know the origin of that asymmetry. It it not enough to say “it just does it”. We’re doing science, not religion or some other such non-minimalist endeavour.

    Cheers,

    -cvj

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