The Standard Model contains at least three sources of CP violation. The first of these, involving the Cabibbo–Kobayashi–Maskawa matrix in the quark sector, has been observed experimentally and can only account for a small portion of the CP violation required to explain the matter-antimatter asymmetry.

The strong interaction should also violate CP, in principle, but turns out that it doesn't, CP violation in the strong sector is also too small to account for the necessary CP violation in the early universe.

Same for PMS matrix in the Neutrino sector.

But, how do I measure the CP necessary?

  • $\begingroup$ You are using the word "measure" but the question seems to be asking for another theoretical source of CP violation. Or do I misunderstand? $\endgroup$ Commented Jun 3, 2014 at 15:33
  • 1
    $\begingroup$ No, it is , to calculate te necessary CP. $\endgroup$
    – IamZack
    Commented Jun 3, 2014 at 15:41

1 Answer 1


We have a pretty good idea of the thermal history of the universe. Combining this with the Sakharov criteria for baryogenesis allows one to calculate the necessary CP violation in terms of the strength of the bayon-number violating interaction and how far out of equilibrium the universe was.

Taking a purely SM approach and having only sphalerons as baryon-number violating interactions in combination with the standard big bang evolution of the universe leaves one with too little CP violation in the sphaleron interactions.

Therefore one needs to find either new baryon number violation, new CP violation or a deviation from the standard big bang evolution.


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