https://doi.org/10.1140/epjc/s10052-016-3947-6
Regular Article - Experimental Physics
Measurement of the radiative decay of polarized muons in the MEG experiment
1
INFN Sezione di Pisa; Dipartimento di Fisica, dell’Università, Largo B. Pontecorvo 3, 56127, Pisa, Italy
2
Scuola Normale Superiore, Piazza dei Cvalieri 7, 56127, Pisa, Italy
3
Paul Scherrer Institut PSI, 5232, Villigen, Switzerland
4
Swiss Federal Institute of Technology ETH, 8093, Zurich, Switzerland
5
ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
6
INFN Sezione di Genova; Dipartimento di Fisica, dell’Università, Via Dodecaneso 33, 16146, Genoa, Italy
7
INFN Sezione di Pavia; Dipartimento di Fisica, dell’Università, Via Bassi 6, 27100, Pavia, Italy
8
INFN Sezione di Lecce; Dipartimento di Matematica e Fisica, dell’Università del Salento, Via per Arnesano, 73100, Lecce, Italy
9
INFN Sezione di Roma; Dipartimento di Fisica, dell’Università “Sapienza”, Piazzale A. Moro, 00185, Rome, Italy
10
Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences, 630090, Novosibirsk, Russia
11
Novosibirsk State Technical University, 630092, Novosibirsk, Russia
12
Novosibirsk State University, 630090, Novosibirsk, Russia
13
KEK, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
14
University of California, Irvine, CA, 92697, USA
15
Joint Institute for Nuclear Research, 141980, Dubna, Russia
16
INFN, Laboratori Nazionali di Frascati, Via E. Fermi, 40-00044, Frascati, Rome, Italy
* e-mail: uchiyama@icepp.s.u-tokyo.ac.jp
Received:
21
December
2015
Accepted:
9
February
2016
Published online:
29
February
2016
We studied the radiative muon decay μ+ →
e+νν̅γ by using for the first time an almost fully polarized muon source. We identified a large sample (~13,000) of these decays in a total sample of 
positive muon decays collected in the MEG experiment in the years 2009–2010 and measured the branching ratio
for 
and 
, consistent with the Standard Model prediction. The precise measurement of this decay mode provides a basic tool for the timing calibration, a normalization channel, and a strong quality check of the complete MEG experiment in the search for 
process.
© The Author(s), 2016
