A study of the radiative KL→π±e ∓νγ decay and search for direct photon emission with the KLOE detector

Abstract

We present a measurement of the ratio R=Γ(K0e3γ;E*γ > 30 MeV, θ*γ>20°)/ Γ(K0e3) and a first measurement of the direct emission contribution in semileptonic KL decays. The measurement was performed at the DA NE φ factory by selecting φ→KLK S decays with the KLOE detector. We use 328 pb-1 of data, corresponding to about 3.5 million K0e3 events and about 9000 K0e3γ radiative events. Our result is R=(924±23stat±16syst)×10-5 for the branching ratio and =-2.3±1.3stat±1. 4syst for the effective strength parameter describing direct emission. © 2008 Springer-Verlag / Società Italiana di Fisica.