Measurement Of The Decay Rate Of The Radiative K-E3(0) Decay

Data from the NA31 experiment at CERN have been used to measure the decay K-L --> pi(+/-)e(-/+)v gamma (K-e3 gamma(0)). 1384 +/- 53 events of this decay type have been observed, The decay rate relative to K-e3(0) is found to be Gamma(K-e3 gamma(0), E(gamma)* greater than or equal to 30 MeV, Theta(e-gamma)* greater than or equal to 20 degrees)/Gamma(K-e3(0)) = (0.934 +/- 0.036(stat.)(-0.039)(+0.055)(syst.))% which corresponds to a branching ratio of BR(K-e3 gamma(0),E(gamma)* greater than or equal to 30 MeV, Theta(e-gamma)* greater than or equal to 20 degrees) = (0.361 +/- 0.014(stat.)(-0.015)(+0.021)(syst.))%. The result is in good agreement with theoretical predictions, The decay K-L --> pi(+/-)e(-/+)v gamma is found to be dominated by internal bremsstrahlung.