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Q & A: How do neutral kaon -decays violate CP?

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Most recent answer: 06/07/2015
How do neutral kaon -decays violate CP?
- Mace (age 17)

Hello Mace,

There are a variety of examples that involve CP violation in K decays, see:  .  Perhaps the most simple one is the ratio of decay rates

  K0L -> π+ + e- + ν e  and   K0L -> π- + e+ + ν~ e .   If CP were not violated the rates would be the same.  They are measured to be slightly different.

Many experiments show that the strong interactions do not violate CP invariance.  It is the weak interaction that is the culprit.    This leads to an unsolved puzzle in the makeup of the universe:  there is an overwhelming abundance of ordinary matter around while there are only a few anti-matter particles.  This calls for CP violation in the early universe, otherwise all the matter and anti-matter would annihilate and the only thing left over would be photons.   Calculations show that the weak interaction is not enough to supply this fact.   We just don't know the answer to this puzzle.  


(published on 06/07/2015)

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