title: New constraint on the existence of the μ+ → e+ γ decay.
abstract: The analysis of a combined data set, totaling 3.6 × 10(14) stopped muons on target, in the search for the lepton flavor violating decay μ(+) → e(+)γ is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of 5.7 × 10(-13) (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.
authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland and Swiss Federal Institute of Technology ETH, CH-8093 Zürich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Adam
authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: X
authors.initials: X
authors.lastname: Bai
authors.affiliation: INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
authors.forename: A M
authors.initials: AM
authors.lastname: Baldini
authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan and KEK, High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan and University of California, Irvine, California 92697, USA.
authors.forename: E
authors.initials: E
authors.lastname: Baracchini
authors.affiliation: INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy and Dipartimento di Fisica, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Bemporad
authors.affiliation: INFN Sezione di Pavia, dell'Università, Via Bassi 6, 27100 Pavia, Italy and Dipartimento di Fisica, dell'Università, Via Bassi 6, 27100 Pavia, Italy.
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authors.affiliation: INFN Sezione di Pavia, dell'Università, Via Bassi 6, 27100 Pavia, Italy.
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authors.initials: PW
authors.lastname: Cattaneo
authors.affiliation: INFN Sezione di Roma, dell'Università "Sapienza", Piazzale A. Moro, 00185 Roma, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Cavoto
authors.affiliation: INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy and Dipartimento di Fisica, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
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authors.lastname: Cei
authors.affiliation: INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Cerri
authors.affiliation: INFN Sezione di Pavia, dell'Università, Via Bassi 6, 27100 Pavia, Italy and Dipartimento di Fisica, dell'Università, Via Bassi 6, 27100 Pavia, Italy.
authors.forename: A
authors.initials: A
authors.lastname: de Bari
authors.affiliation: INFN Sezione di Genova, dell'Università, Via Dodecaneso 33, 16146 Genova, Italy and Dipartimento di Fisica, dell'Università, Via Dodecaneso 33, 16146 Genova, Italy.
authors.forename: M
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authors.lastname: De Gerone
authors.affiliation: Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
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authors.lastname: Doke
authors.affiliation: INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
authors.forename: S
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authors.lastname: Dussoni
authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Egger
authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Fujii
authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland and INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Galli
authors.affiliation: INFN Sezione di Genova, dell'Università, Via Dodecaneso 33, 16146 Genova, Italy and Dipartimento di Fisica, dell'Università, Via Dodecaneso 33, 16146 Genova, Italy.
authors.forename: F
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authors.lastname: Gatti
authors.affiliation: University of California, Irvine, California 92697, USA.
authors.forename: B
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authors.affiliation: INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
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authors.lastname: Grassi
authors.affiliation: INFN Sezione di Roma, dell'Università "Sapienza", Piazzale A. Moro, 00185 Roma, Italy.
authors.forename: A
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authors.lastname: Graziosi
authors.affiliation: Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia and Novosibirsk State Technical University, 630092 Novosibirsk, Russia.
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authors.affiliation: KEK, High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
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authors.lastname: Haruyama
authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland.
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authors.lastname: Hildebrandt
authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Y
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authors.lastname: Hisamatsu
authors.affiliation: Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia.
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authors.lastname: Ignatov
authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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authors.lastname: Iwamoto
authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: D
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authors.lastname: Kaneko
authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland.
authors.forename: P-R
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authors.lastname: Kettle
authors.affiliation: Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia.
authors.forename: B I
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authors.affiliation: Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia.
authors.forename: N
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authors.lastname: Khomotov
authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland.
authors.forename: O
authors.initials: O
authors.lastname: Kiselev
authors.affiliation: Joint Institute for Nuclear Research, 141980 Dubna, Russia.
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authors.lastname: Korenchenko
authors.affiliation: Joint Institute for Nuclear Research, 141980 Dubna, Russia.
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authors.lastname: Kravchuk
authors.affiliation: University of California, Irvine, California 92697, USA.
authors.forename: G
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authors.affiliation: KEK, High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
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authors.affiliation: KEK, High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Mihara
authors.affiliation: University of California, Irvine, California 92697, USA.
authors.forename: W
authors.initials: W
authors.lastname: Molzon
authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: T
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authors.lastname: Mori
authors.affiliation: Joint Institute for Nuclear Research, 141980 Dubna, Russia.
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authors.lastname: Mzavia
authors.affiliation: INFN Sezione di Pavia, dell'Università, Via Bassi 6, 27100 Pavia, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Nardò
authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland and ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan and KEK, High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Natori
authors.affiliation: INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy and Dipartimento di Fisica, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
authors.forename: D
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authors.lastname: Nicolò
authors.affiliation: KEK, High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: H
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authors.lastname: Nishiguchi
authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Y
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authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: W
authors.initials: W
authors.lastname: Ootani
authors.affiliation: INFN Sezione di Lecce, dell'Università, Via per Arnesano, 73100 Lecce, Italy and Dipartimento di Fisica, dell'Università, Via per Arnesano, 73100 Lecce, Italy.
authors.forename: M
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authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland.
authors.forename: A
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authors.affiliation: INFN Sezione di Roma, dell'Università "Sapienza", Piazzale A. Moro, 00185 Roma, Italy.
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authors.affiliation: Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia.
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authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland and INFN Sezione di Roma, dell'Università "Sapienza", Piazzale A. Moro, 00185 Roma, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Renga
authors.affiliation: INFN Sezione di Roma, dell'Università "Sapienza", Piazzale A. Moro, 00185 Roma, Italy and Dipartimento di Fisica, dell'Università "Sapienza", Piazzale A. Moro, 00185 Roma, Italy.
authors.forename: E
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authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland.
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authors.affiliation: INFN Sezione di Pavia, dell'Università, Via Bassi 6, 27100 Pavia, Italy.
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authors.affiliation: INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
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authors.affiliation: INFN Sezione di Pisa, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy and Dipartimento di Fisica, dell'Università, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
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authors.affiliation: University of California, Irvine, California 92697, USA.
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authors.affiliation: Paul Scherrer Institut PSI, CH-5232 Villigen, Switzerland and ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Y
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authors.lastname: Uchiyama
authors.affiliation: INFN Sezione di Roma, dell'Università "Sapienza", Piazzale A. Moro, 00185 Roma, Italy.
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authors.initials: C
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authors.affiliation: University of California, Irvine, California 92697, USA.
authors.forename: F
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authors.affiliation: KEK, High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
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authors.affiliation: ICEPP, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: S
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authors.affiliation: University of California, Irvine, California 92697, USA.
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authors.affiliation: INFN Sezione di Roma, dell'Università "Sapienza", Piazzale A. Moro, 00185 Roma, Italy.
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