Measurement of the decay rate of the radiative Ke30 decay

Abstract Data from the NA31 experiment at CERN have been used to measure the decay K L → π ± e ± νγ ( K e 3 γ 0 ). 1384 ± 53 events of this decay type have been observed. The decay rate relative to K e 3 0 is found to be Γ(K e3γ 0 , E γ ∗ ≥ 30 MeV , Θ e-γ ∗ ≥ 20°) Γ(K e3 0 ) = (0.934 ± 0.036 ( stat. ) −0.039 +0.055 ( syst. )) % which corresponds to a branching ratio of BR (K e3γ 0 , E γ ∗ ≥ 30 MeV , Θ e-γ ∗ ≥ 20°) = (0.361 ± 0.014 ( stat. ) −0.015 +0.021 ( syst. )) %. The result is in good agreement with theoretical predictions. The decay K L → π ± e ± νγ is found to be dominated by internal bremsstrahlung.