Rare Decay of K Meson

Abstract

We investigate the rare decay processes of the K mesons, K_{L,S} -> π^0 ν\barν and K^{+} -> π^+ ν\barν in LR model with lepton family number being well conserved. In these processes, scalar operators (\bar{s}d)(\barν_τν_τ), which are derived from box diagram in LR model, play an important role due to an enhancement factor M_{K}/m_{s} in the matrix element $<π|\bar{s}d|K>$. It is emphasized that the K_{L} decay process through the scalar operator is not the CP violating mode, so the B(K_L -> π^{0} ν\barν) remains non-zero even in the CP conserved limit. We present the pion energy spectrum for these processes and discuss the effects of LR model.