Decays KL, S → π0π0γ and KL, S → π0π0e+e− as probes of chiral dynamics

Abstract

The decays K L, S → π 0 π 0 γ are examples of quadrupole transitions (E 2 and M 2 respectively) which are forbidden in chiral perturbation theory (ChPT) at O(p 4 ). At the same time, the virtual photon amplitude K L → π 0π 0γ ∗ is calculable in ChPT. Using a plausible estimate for the real photon amplitude K L → π 0 π 0 γ, we show that the decay rate of K L → π 0 π 0 e + e − contains comparable contributions from the E2 and virtual photon mechanisms, and that the two components can be clearly distinguished in the invariant mass spectrum of the e + e − pair.