The radiative decay of the muon, positive-muon to position + neutrino + e-neutrino + mu'-antineutrino was measured using muons from the Columbia University Nevis Synchrocyclotron. The positron and gamma-ray decay products were observed at relative angles near 180 degrees, using scintillation counters and two 9 in. x 10 in. NaI crystals, which enabled simultaneous measurement of the positron and gamma energies. The pulses from the crystals were displayed on oscilloscopes and photographed, and the measured amplitudes of these pulses were calibrated using the positron spectrum of the nonradiative decay. The two-dimensional energy spectrum for positrons and gammas was obtained for about 900 events, after subtraction of background. This spectrum and the measured rate, obtained by normalizing to the nonradiative decay, were compared with theoretical predictions for the radiative decay. The results were in good agreement with the theory, within statistics, for the case of pure V-A coupling. (Author).

A measurement of the radiative muon decay [mu] --> e v e̳ v [m̳u̳] [gamma] branching fraction was done on the basis of the radiative decay data of MEG experiment. The data were taken periodically one day per week with the beam intensity of 1.2x106 [mu] + / s from September to December, 2008. The positron was measured by a spectrometer with gradient magnetic field. The photon was detected by an innovative ̃900 liter liquid xenon scintillation detector. The measurement was carried out with a cut-and-count approach. We report the radiative muon decay branching fraction to be B([mu] --> e vv̄ [gamma]) = (2.84 ± 0.20(stat) ± 0.05(syst))x10−7, with Ee̳> 46 MeV, E [gamma]> 30 MeV, and the opening angle between the two particles [theta] e̳ [gamma] in its full kinematic range. Distributions of three observables, E e̳, E [gamma], and [theta] e̳ [gamma], as well as their kinematic correlations were verified to be consistent with the radiative decays. The measurement is in excellent agreement with the prediction of the Standard Model.