CP violation: why not in K*, B* vector mesons?

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Discussion Overview

The discussion revolves around the topic of CP violation in mesons, specifically questioning why CP violation has been observed in neutral K and B mesons but not in spin 1 mesons like K* and B*. The scope includes theoretical considerations and experimental challenges related to particle physics.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants note that CP violation has been measured in neutral K and B mesons, but express concern over the limited number of systems available for such measurements.
  • One participant suggests that the K* and B* mesons, being spin 1, may not exhibit CP violation due to their decay mechanisms, which are different from those of spin 0 mesons.
  • Another participant points out that CP violation is associated with weak decays, implying that the decay processes of K* and B* may not allow for such observations.
  • A later reply questions whether particle-antiparticle mixing could be observed in neutral K* and B*, but another participant asserts that mixing is also a weak process and not observable in these mesons due to their short lifetimes.

Areas of Agreement / Disagreement

Participants generally agree that CP violation is linked to weak decays and that the decay characteristics of K* and B* mesons present challenges for observing such phenomena. However, there is no consensus on whether the inability to observe CP violation in these mesons is due to fundamental reasons or experimental difficulties.

Contextual Notes

Limitations include the dependence on the specific decay processes of the mesons and the implications of their lifetimes on the observability of mixing and CP violation.

franoisbelfor
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Experimentalists have measured CP violation in neutral K and B mesons.
Everybody is unhappy that so far there are only 2 systems so
for which these measurements are possible.
(Neutral D mesons are predicted to show such a small effect that it
is probably unmeasurable for a long time.)
All these are spin 0 mesons.

But why is it not possible to test CP violation also in spin 1 mesons,
such as K* and B*? Is there a fundamental reason or is it simply that
experiments are too difficult?

François
 
Physics news on Phys.org
The K* decays strongly and the B* decays electromagnetically, and CP violation is a phenomenon that occurs in weak decays.
 
Vanadium 50 said:
The K* decays strongly and the B* decays electromagnetically, and CP violation is a phenomenon that occurs in weak decays.

Ah, thanks for the clarification. Could it then at least be possible to observe particle-antiparticle mixing, for the neutral K* and B*? Or is that also only visible in weak decays?

François
 
I'm afraid not.

Mixing is second-order weak. Neither the K* nor B* last long enough to observe this, by many orders of magnitude.
 

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