Eur. Phys. J. C (2016) 76: 434
https://doi.org/10.1140/epjc/s10052-016-4271-x

Regular Article - Experimental Physics

Search for the lepton flavour violating decay with the full dataset of the MEG experiment

MEG Collaboration

¹ Paul Scherrer Institut PSI, 5232, Villigen, Switzerland
² Swiss Federal Institute of Technology ETH, CH-8093, Zurich, Switzerland
³ ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
⁴ INFN Sezione di Pisa, dell’Università, Largo B. Pontecorvo 3, 56127, Pisa, Italy
⁵ Dipartimento di Fisica, dell’Università, Largo B. Pontecorvo 3, 56127, Pisa, Italy
⁶ Scuola Normale Superiore, Piazza dei Cavalieri, 56127, Pisa, Italy
⁷ University of California, Irvine, CA, 92697, USA
⁸ INFN Sezione di Pavia, dell’Università, Via Bassi 6, 27100, Pavia, Italy
⁹ Dipartimento di Fisica, dell’Università, Via Bassi 6, 27100, Pavia, Italy
¹⁰ INFN Sezione di Roma, dell’Università “Sapienza”, Piazzale A. Moro, 00185, Rome, Italy
¹¹ Dipartimento di Fisica, dell’Università “Sapienza”, Piazzale A. Moro, 00185, Rome, Italy
¹² INFN Sezione di Genova, dell’Università, Via Dodecaneso 33, 16146, Genoa, Italy
¹³ Dipartimento di Fisica, dell’Università, Via Dodecaneso 33, 16146, Genoa, Italy
¹⁴ Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, 169-8555, Japan
¹⁵ Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences, 630090, Novosibirsk, Russia
¹⁶ KEK, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
¹⁷ Joint Institute for Nuclear Research, 141980, Dubna, Russia
¹⁸ INFN Sezione di Lecce, dell’Università del Salento, Via per Arnesano, 73100, Lecce, Italy
¹⁹ Dipartimento di Matematica e Fisica, dell’Università del Salento, Via per Arnesano, 73100, Lecce, Italy
²⁰ Novosibirsk State Technical University, 630092, Novosibirsk, Russia
²¹ Novosibirsk State University, 630090, Novosibirsk, Russia
²² Present address: INFN, Laboratori Nazionali di Frascati, Via E. Fermi, 40-00044, Frascati, Rome, Italy
²³ Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK

^* e-mail: fabrizio.cei@pi.infn.it

Received: 1 June 2016
Accepted: 11 July 2016
Published online: 3 August 2016

Abstract

The final results of the search for the lepton flavour violating decay based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013 and totalling stopped muons on target are presented. No significant excess of events is observed in the dataset with respect to the expected background and a new upper limit on the branching ratio of this decay of (90 % confidence level) is established, which represents the most stringent limit on the existence of this decay to date.