Measurement of the decay rate of the radiative Ke30 decay

Data from the NA31 experiment at CERN have been used to measure the decay KL → π±e±νγ (Ke3γ0). 1384 ± 53 events of this decay type have been observed. The decay rate relative to Ke30 is found to be Γ(Ke3γ0, Eγ∗ ≥ 30 MeV, Θe-γ∗ ≥ 20°)Γ(Ke30) = (0.934 ± 0.036 (stat.) −0.039+0.055 (syst.)) % which corresponds to a branching ratio of BR(Ke3γ0, Eγ∗ ≥ 30 MeV, Θe-γ∗ ≥ 20°) = (0.361 ± 0.014 (stat.)−0.015+0.021 (syst.))%. The result is in good agreement with theoretical predictions. The decay KL → π±e±νγ is found to be dominated by internal bremsstrahlung.