## Physics Questions People Ask Fermilab

**Patterns in CP violation**

**You asked:**

I was wondering if there were any mathematical patterns noticed in CP
violation experiments, especially in regard to relationships between matter
and antimatter, the rate of decay and so forth.

Errol

Dear Errol,

When you talk about mathematical patterns, I assume you have in mind some symmetries. Well, CP violation is just the absence of a symmetry, and physicists talk about the asymmetry between matter and antimatter. If it wouldn't be for this tiny flaw in symmetry, a universe made out of antimatter would behave in exactly the same manner as a universe made out of matter. Physicists, however, have observed that this is not the case. Certain antimatter particles show slightly different decay properties than the corresponding matter particles. This has been known for a long time in the case of strange quarks, but know physicists start to see similar CP violation signs in the case of bottom quarks.

For the CP violation of particles involving bottom quarks, the description of CP violation is summarized in a graphic called the unitarity triangle. If CP symmetry would be perfect, then that triangle would be flat: it would be a line. The angle beta in the following diagram would be zero: http://www.fnal.gov/pub/ferminews/ferminews00-08-25/standard.pdf

Recent experimental results indicate that the angle beta is larger than 0 and less than 45 degrees: not a strong constraint yet. Within the next two years physicists expect much more precise results. Then they will be able to say whether the angle beta is, say, 20 degrees or 40 degrees. The experiments necessary to do these measurements take place at SLAC, California, and KEK, Japan. Fermilab will also carry out measurements in the near future.

To learn more about the topic I recommend that you read an article in FermiNews: http://www.fnal.gov/pub/ferminews/Ferminews00-08-25.pdf Pages 2 to 5.

You may also want to take a look at the webpages for the general public provided by SLAC: http://www2.slac.stanford.edu/vvc/experiments/babar.html

Best wishes,

Kurt Riesselmann

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- 04/28/2014
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