Measurement of inner Bremsstrahlung in polarized muon decay with MEG

Adam, J.; Bai, X.; Baldini, A.M.; Baracchini, E.; Bemporad, C.; Boca, G.; Cattaneo, P.W.; Cavoto, G.; Cei, F.; Cerri, C.; De Gerone, M.; Egger, J.; Galli, G.; Hildebrandt, M.; Kettle, P.-R.; Kiselev, O.; Papa, A.; Renga, F.; Ritt, S.; Uchiyama, Y.; Zanello, D.

doi:10.1016/j.nuclphysbps.2014.02.019

Measurement of inner Bremsstrahlung in polarized muon decay with MEG

Adam J, Bai X, Baldini AM, Baracchini E, Bemporad C, Boca G, Cattaneo PW, Cavoto G, Cei F, Cerri C, De Gerone M, Egger J, Galli G, Hildebrandt M, Kettle P-R, Kiselev O, Papa A, Renga F, Ritt S, Uchiyama Y, Zanello D, et al.

Citation

Adam, J., Bai, X., Baldini, A. M., Baracchini, E., Bemporad, C., Boca, G., … Zanello, D. (2014). Measurement of inner Bremsstrahlung in polarized muon decay with MEG. Nuclear Physics B - Proceedings Supplements: Vol. 248-250. (pp. 108-111). Presented at the 1st conference on charged lepton flavor violation. https://doi.org/10.1016/j.nuclphysbps.2014.02.019

Persistent URL https://www.dora.lib4ri.ch/psi/islandora/object/psi:22995

A muon decay accompanied by a photon through the inner Bremmstrahlung process (μ→eνν^-γ, radiative muon decay) produces a time-correlated pair of positron and photon which becomes one of the main backgrounds in the search for μ→ eγ decay. This channel is also an important probe of timing calibration and cross-check of whole the experiment. We identified a large sample (~ 13000) of radiative muon decays in MEG data sample. The measured branching ratio in a region of interest in the μ→ eγ search is consistent with the standard model prediction. It is also the first measurement of the decay from polarized muons. The precision measurement of this mode enables us to use it as one of the normalization channels of μ→ eγ decay successfully reducing its uncertainty to less than 5%.