# Fitch and Cronin experiment

1. Jul 2, 2013

### sunrah

The Fitch and Cronin experiment is put forward as one of the very few examples of CP violation in weak interactions and as a possible explanation for matter anti-matter asymmetry.
The decay channels are

K → 3 pions
K → pi-plus + electron + antineutrino
K → pi-minus + positron + neutrino

Of these the neutral kaons prefer to decay into the positron channel. Griffith's says that if CP weren't violated these last two decays would have an equal probability of happening. How can a preference for antimatter can be used to explain a dominance of matter? Also in the second decay an antineutrino is produced is this somehow less important in this respect than the positron?

2. Jul 2, 2013

### Bill_K

This paper gives a detailed analysis of the semileptonic decays, and shows that CP violation makes them unequal. (Eqs.(2.47-8))

To get the dominance of matter over antimatter, CP violation must be somehow involved, but the details remain shrouded in mystery. There is not an obvious connection with the kaon decays.

"The explanation of how you possibly can make more particles than antiparticles always leads in the end to some explanation that basically just states that you need to be able to somehow make more particles than antiparticles." - Sascha Vongehr

Last edited: Jul 2, 2013