An experimental investigation of the radiative structure decay K + → e +υγ

Abstract

The decay K + → e + υγ has been investigated. For the structure-dependent part with positive γ-helicity (SD +) the branching ratio Γ( SD +) Γ( K μ2 ) = (2.33 ± 0.42) × 10 −5 is obtained from 51 ± 3 events observed in the kinematical region E e ⩾ 235 MeV, E γ > 48 MeV and θ e γ > 140°. For the corresponding part with negative γ-helicity we obtain an upper limit Γ(SD −)/ Γ(SD +) < 11 (90% CL) from the sample of electrons with energies 220 MeV ⩽ E e < 230 MeV and with no γ in the backward direction. This upper limit implies that the ratio of structure-dependent axial vector amplitudes lies outside the region −1.8 < a K υ K < −0.54 . For the decay K + → e +νν ν the limit Γ( K + → e +νν ν)/Γ( K e2 ) < 3.8 90% confidence level) was found.