top that: quark soup, time travel and the end of the internet

From Gordon via Chad Fermilab is claiming single top quark decay to b quark + W

ie the accelerator produced a t-quark as part of some quark/anti-quark ensemble, without simultaneously producing an anti-t-quark.

So what does this all mean...

well, there are three generations of quarks - the up and down, from which all normal baryonic matter is made (ie protons and neutrons); strange and charming; and bottom and top (aka beauty and truth) - with top being the heaviest.

The three generations, or "flavours", essentially duplicate each other in key properties, except the successive quark pairs are more massive.
Why this should be is related to some deep underlying symmetries of particle physics, but one of the interesting consequences of there being three generations is that the different generations can "mix" - crudely speaking there are some quantum mechanical properties of each quark that look like a mix of the properties of the three generations of quarks.
The strength of this mixing is measured by the Kobayashi-Maskawa matrix and the value of this matrix essentially describes the probability that a quark of one "flavour" generation can transform to another through flavour changing weak decays. Normally this is seen through the decay of the heavier quarks, made in quark-anti-quark bound pairs; but, clearly, the reverse process must occur, so there is a small but finite probability if you inject enough energy into a quark ensemble that you will boost some quark up in flavour, and so transform a charm or up quark to a top quark.

The KM matrix is important, because if there are three generation entries in it, and they mix to non-zero degree, then the symmetry of parity with charge conjugation is not conserved.
Parity is symmetry under mirror reflectionl; charge conjugation is roughly the symmetry of exchanging positive and negative electric charges.

So the product CP is not conserved, and we know that, but measuring it is important.
One reason for that is the bigger symmetry CPT is conserved.
Here T is time reversal symmetry, and we can conclude that if CP is not generally conserved, but CPT is conserved, then T-symmetry must be violated.

That is to say, the universe is not symmetric under time reversal, which is interesting. And in principle the measurement of top quark formation will tell us what is going on with that.

One interesting aspect of violation of T-symmetry is that the asymmetry between matter andanti-matter (there is less anti-matter in the universe then matter, leaving a residue of matter when all is said and done, ie us) is tied to the T-symmetry violation.

ie if we couldn't make single top quarks, then the amount of matter and anti-matter would balance perfectly in the universe, and all would promptly annihilate leaving only a thermal radiation bath.
This would also probably mean the end of the internet.

So, we learn something important.
More data is needed.

Still don't think they're going to see the Higgs though...

Lubos has stuff on this also