The “superweak” interaction, imagined by Lincoln Wolfenstein, was intended to explain CP violation in neutral kaon decay by postulating a |ΔS| = 2 interaction which would change K0 to K0bar. In this model, the only CP violation in the kaon system would be indirect. The observation of direct CP violation in kaon decays, and its agreement with the Standard Model KM mechanism, rules out such a force.

Well, you asked.