CP violation refers to a very deep feature of our universe, a breakdown of something called CP symmetry. The “C” stands for charge conjugation, and the “P” for parity.
C symmetry would be if the laws of physics were identical if every particle in the universe were swapped with its corresponding antiparticle (and vice versa).
P symmetry would be if the laws of physics were identical if left and right were swapped, or the physics of a mirror-image universe were identical to ours.
CP symmetry is both C and P symmetry, together – particle-antiparticles swapped AND left-right swapped.
Of the four fundamental forces we know about – gravity, electromagnetism, the weak interaction (weak nuclear force), and the strong interaction (strong nuclear force) – the first two and the last seem to be symmetric under C and P separately. However, the weak was shown to violate P symmetry in the 1950s (T.D. Lee and C.N. Yang won the Nobel Prize for Physics, in 1957, for their work on this).
The first experiments to show CP violation – involving neutral kaons – were done in 1964 (Cronin and Fitch were awarded the Nobel Prize for Physics, in 1980, for their work on this … symmetry violations are fertile ground for Nobels!), and the extensive work done in so-called B factories (experiments on the decay of B mesons) in the early years of this century showed CP violation is not just a kaon phenomenon, but a feature of the weak interaction.
CP violation (or something much like it) is, very likely, why you are able to read these words today! Without CP violation, the universe would not have far more particles than antiparticles; they’d have almost all annihilated with the antiparticles during the time in the early, hot universe when baryons were formed.
But there’s a mystery: the CP violation discovered in B factories (and kaon experiments) – and incorporated into particle physics’ Standard Model – does not give rise the matter-antimatter asymmetry we observe in today’s universe.
As CP violation is such a big deal in particle physics, no surprise that there’s LOTS of material on it, out there on the web. Here are a few sites you might like to check out: CP News (University of Cincinnati), Why does CP violation matter to the universe? (CERN Courier), and CP Violation and B Physics (Stanford University).
Are there any Universe Today stories featuring CP violation? Sure! New Differences Between Matter and Antimatter, Why There’s More Matter Than Antimatter in the Universe, and Did Dark Matter Annihilate in Our Early Universe?
Antimatter, an Astronomy Cast episode, explores CP violation in more detail – check it out!
Source: Wikipedia
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