We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, $$\upmu ^+ \rightarrow \mathrm {e}^+\mathrm {X}, \mathrm {X} \rightarrow \upgamma \upgamma \ $$ . This search uses a dataset resulting from $$7.5\times 10^{14}$$ stopped muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013. No significant excess is found in the mass region 20–45 MeV/c $$^2$$ for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20–40 MeV/c $$^2$$ , down to $${\mathcal {O}}(10^{-11})$$ at 90% confidence level.
{
"_oai": {
"updated": "2020-12-17T00:38:11Z",
"id": "oai:repo.scoap3.org:57048",
"sets": [
"EPJC"
]
},
"authors": [
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pisa dell\u2019Universit\u00e0, Largo B. Pontecorvo 3, Pisa, 56127, Italy",
"organization": "INFN Sezione di Pisa dell\u2019Universit\u00e0"
}
],
"surname": "Baldini",
"given_names": "A.",
"full_name": "Baldini, A."
},
{
"affiliations": [
{
"country": "Switzerland",
"value": "Paul Scherrer Institut PSI, Villigen, 5232, Switzerland",
"organization": "Paul Scherrer Institut PSI"
},
{
"country": "Switzerland",
"value": "Swiss Federal Institute of Technology ETH, Zurich, 8093, Switzerland",
"organization": "Swiss Federal Institute of Technology ETH"
}
],
"surname": "Berg",
"given_names": "F.",
"full_name": "Berg, F."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Genova dell\u2019Universit\u00e0, Via Dodecaneso 33, Genoa, 16146, Italy",
"organization": "INFN Sezione di Genova dell\u2019Universit\u00e0"
}
],
"surname": "Biasotti",
"given_names": "M.",
"full_name": "Biasotti, M."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pavia dell\u2019Universit\u00e0, Via Bassi 6, Pavia, 27100, Italy",
"organization": "INFN Sezione di Pavia dell\u2019Universit\u00e0"
}
],
"surname": "Boca",
"given_names": "G.",
"full_name": "Boca, G."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pavia dell\u2019Universit\u00e0, Via Bassi 6, Pavia, 27100, Italy",
"organization": "INFN Sezione di Pavia dell\u2019Universit\u00e0"
}
],
"surname": "Cattaneo",
"given_names": "P.",
"full_name": "Cattaneo, P."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d, Piazzale A. Moro, Rome, 00185, Italy",
"organization": "INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d"
}
],
"surname": "Cavoto",
"given_names": "G.",
"full_name": "Cavoto, G."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pisa dell\u2019Universit\u00e0, Largo B. Pontecorvo 3, Pisa, 56127, Italy",
"organization": "INFN Sezione di Pisa dell\u2019Universit\u00e0"
}
],
"surname": "Cei",
"given_names": "F.",
"full_name": "Cei, F."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pisa dell\u2019Universit\u00e0, Largo B. Pontecorvo 3, Pisa, 56127, Italy",
"organization": "INFN Sezione di Pisa dell\u2019Universit\u00e0"
}
],
"surname": "Chiappini",
"given_names": "M.",
"full_name": "Chiappini, M."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d, Piazzale A. Moro, Rome, 00185, Italy",
"organization": "INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d"
}
],
"surname": "Chiarello",
"given_names": "G.",
"full_name": "Chiarello, G."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Matematica e Fisica, INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento, Via per Arnesano, Lecce, 73100, Italy",
"organization": "INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento"
}
],
"surname": "Chiri",
"given_names": "C.",
"full_name": "Chiri, C."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Matematica e Fisica, INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento, Via per Arnesano, Lecce, 73100, Italy",
"organization": "INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento"
}
],
"surname": "Corvaglia",
"given_names": "A.",
"full_name": "Corvaglia, A."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pavia dell\u2019Universit\u00e0, Via Bassi 6, Pavia, 27100, Italy",
"organization": "INFN Sezione di Pavia dell\u2019Universit\u00e0"
}
],
"surname": "Bari",
"given_names": "A.",
"full_name": "Bari, A."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Genova dell\u2019Universit\u00e0, Via Dodecaneso 33, Genoa, 16146, Italy",
"organization": "INFN Sezione di Genova dell\u2019Universit\u00e0"
}
],
"surname": "Gerone",
"given_names": "M.",
"full_name": "Gerone, M."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pisa dell\u2019Universit\u00e0, Largo B. Pontecorvo 3, Pisa, 56127, Italy",
"organization": "INFN Sezione di Pisa dell\u2019Universit\u00e0"
}
],
"surname": "Francesconi",
"given_names": "M.",
"full_name": "Francesconi, M."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pisa dell\u2019Universit\u00e0, Largo B. Pontecorvo 3, Pisa, 56127, Italy",
"organization": "INFN Sezione di Pisa dell\u2019Universit\u00e0"
}
],
"surname": "Galli",
"given_names": "L.",
"full_name": "Galli, L."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Genova dell\u2019Universit\u00e0, Via Dodecaneso 33, Genoa, 16146, Italy",
"organization": "INFN Sezione di Genova dell\u2019Universit\u00e0"
}
],
"surname": "Gatti",
"given_names": "F.",
"full_name": "Gatti, F."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Matematica e Fisica, INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento, Via per Arnesano, Lecce, 73100, Italy",
"organization": "INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento"
}
],
"surname": "Grancagnolo",
"given_names": "F.",
"full_name": "Grancagnolo, F."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pisa dell\u2019Universit\u00e0, Largo B. Pontecorvo 3, Pisa, 56127, Italy",
"organization": "INFN Sezione di Pisa dell\u2019Universit\u00e0"
}
],
"surname": "Grassi",
"given_names": "M.",
"full_name": "Grassi, M."
},
{
"affiliations": [
{
"country": "Russia",
"value": "Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090, Russia",
"organization": "Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences"
},
{
"country": "Russia",
"value": "Novosibirsk State Technical University, Novosibirsk, 630092, Russia",
"organization": "Novosibirsk State Technical University"
},
{
"country": "Russia",
"value": "Novosibirsk State University, Novosibirsk, 630090, Russia",
"organization": "Novosibirsk State University"
}
],
"surname": "Grigoriev",
"given_names": "D.",
"full_name": "Grigoriev, D."
},
{
"affiliations": [
{
"country": "Switzerland",
"value": "Paul Scherrer Institut PSI, Villigen, 5232, Switzerland",
"organization": "Paul Scherrer Institut PSI"
}
],
"surname": "Hildebrandt",
"given_names": "M.",
"full_name": "Hildebrandt, M."
},
{
"affiliations": [
{
"country": "Switzerland",
"value": "Paul Scherrer Institut PSI, Villigen, 5232, Switzerland",
"organization": "Paul Scherrer Institut PSI"
},
{
"country": "Switzerland",
"value": "Swiss Federal Institute of Technology ETH, Zurich, 8093, Switzerland",
"organization": "Swiss Federal Institute of Technology ETH"
}
],
"surname": "Hodge",
"given_names": "Z.",
"full_name": "Hodge, Z."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Ieki",
"given_names": "K.",
"full_name": "Ieki, K."
},
{
"affiliations": [
{
"country": "Russia",
"value": "Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090, Russia",
"organization": "Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences"
},
{
"country": "Russia",
"value": "Novosibirsk State University, Novosibirsk, 630090, Russia",
"organization": "Novosibirsk State University"
}
],
"surname": "Ignatov",
"given_names": "F.",
"full_name": "Ignatov, F."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Iwai",
"given_names": "R.",
"full_name": "Iwai, R."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Iwamoto",
"given_names": "T.",
"full_name": "Iwamoto, T."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Kobayashi",
"given_names": "S.",
"full_name": "Kobayashi, S."
},
{
"affiliations": [
{
"country": "Switzerland",
"value": "Paul Scherrer Institut PSI, Villigen, 5232, Switzerland",
"organization": "Paul Scherrer Institut PSI"
}
],
"surname": "Kettle",
"given_names": "P.R.",
"full_name": "Kettle, P.R."
},
{
"affiliations": [
{
"country": "USA",
"value": "University of California, Irvine, CA, 92697, USA",
"organization": "University of California"
}
],
"surname": "Kyle",
"given_names": "W.",
"full_name": "Kyle, W."
},
{
"affiliations": [
{
"country": "JINR",
"value": "Joint Institute for Nuclear Research, Dubna, 141980, Russia",
"organization": "Joint Institute for Nuclear Research"
}
],
"surname": "Khomutov",
"given_names": "N.",
"full_name": "Khomutov, N."
},
{
"affiliations": [
{
"country": "JINR",
"value": "Joint Institute for Nuclear Research, Dubna, 141980, Russia",
"organization": "Joint Institute for Nuclear Research"
}
],
"surname": "Kolesnikov",
"given_names": "A.",
"full_name": "Kolesnikov, A."
},
{
"affiliations": [
{
"country": "JINR",
"value": "Joint Institute for Nuclear Research, Dubna, 141980, Russia",
"organization": "Joint Institute for Nuclear Research"
}
],
"surname": "Kravchuk",
"given_names": "N.",
"full_name": "Kravchuk, N."
},
{
"affiliations": [
{
"country": "JINR",
"value": "Joint Institute for Nuclear Research, Dubna, 141980, Russia",
"organization": "Joint Institute for Nuclear Research"
}
],
"surname": "Kuchinskiy",
"given_names": "N.",
"full_name": "Kuchinskiy, N."
},
{
"affiliations": [
{
"country": "USA",
"value": "University of California, Irvine, CA, 92697, USA",
"organization": "University of California"
}
],
"surname": "Libeiro",
"given_names": "T.",
"full_name": "Libeiro, T."
},
{
"affiliations": [
{
"country": "USA",
"value": "University of California, Irvine, CA, 92697, USA",
"organization": "University of California"
}
],
"surname": "Lim",
"given_names": "G.",
"full_name": "Lim, G."
},
{
"affiliations": [
{
"country": "JINR",
"value": "Joint Institute for Nuclear Research, Dubna, 141980, Russia",
"organization": "Joint Institute for Nuclear Research"
}
],
"surname": "Malyshev",
"given_names": "V.",
"full_name": "Malyshev, V."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Matsuzawa",
"given_names": "N.",
"full_name": "Matsuzawa, N."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d, Piazzale A. Moro, Rome, 00185, Italy",
"organization": "INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d"
}
],
"surname": "Meucci",
"given_names": "M.",
"full_name": "Meucci, M."
},
{
"affiliations": [
{
"country": "Japan",
"value": "KEK, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan",
"organization": "KEK, High Energy Accelerator Research Organization"
}
],
"surname": "Mihara",
"given_names": "S.",
"full_name": "Mihara, S."
},
{
"affiliations": [
{
"country": "USA",
"value": "University of California, Irvine, CA, 92697, USA",
"organization": "University of California"
}
],
"surname": "Molzon",
"given_names": "W.",
"full_name": "Molzon, W."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Mori",
"given_names": "Toshinori",
"full_name": "Mori, Toshinori"
},
{
"affiliations": [
{
"country": "Switzerland",
"value": "Paul Scherrer Institut PSI, Villigen, 5232, Switzerland",
"organization": "Paul Scherrer Institut PSI"
}
],
"surname": "Mtchedilishvili",
"given_names": "A.",
"full_name": "Mtchedilishvili, A."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Nakao",
"email": "mitsutaka.r.nakao@gmail.com",
"full_name": "Nakao, M.",
"given_names": "M."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Natori",
"given_names": "H.",
"full_name": "Natori, H."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pisa dell\u2019Universit\u00e0, Largo B. Pontecorvo 3, Pisa, 56127, Italy",
"organization": "INFN Sezione di Pisa dell\u2019Universit\u00e0"
}
],
"surname": "Nicol\u00f2",
"given_names": "D.",
"full_name": "Nicol\u00f2, D."
},
{
"affiliations": [
{
"country": "Japan",
"value": "KEK, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan",
"organization": "KEK, High Energy Accelerator Research Organization"
}
],
"surname": "Nishiguchi",
"given_names": "H.",
"full_name": "Nishiguchi, H."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Nishimura",
"given_names": "M.",
"full_name": "Nishimura, M."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Ogawa",
"given_names": "S.",
"full_name": "Ogawa, S."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Onda",
"given_names": "R.",
"full_name": "Onda, R."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Ootani",
"given_names": "W.",
"full_name": "Ootani, W."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Oya",
"given_names": "A.",
"full_name": "Oya, A."
},
{
"affiliations": [
{
"country": "USA",
"value": "University of California, Irvine, CA, 92697, USA",
"organization": "University of California"
}
],
"surname": "Palo",
"given_names": "D.",
"full_name": "Palo, D."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Matematica e Fisica, INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento, Via per Arnesano, Lecce, 73100, Italy",
"organization": "INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento"
}
],
"surname": "Panareo",
"given_names": "M.",
"full_name": "Panareo, M."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pisa dell\u2019Universit\u00e0, Largo B. Pontecorvo 3, Pisa, 56127, Italy",
"organization": "INFN Sezione di Pisa dell\u2019Universit\u00e0"
},
{
"country": "Switzerland",
"value": "Paul Scherrer Institut PSI, Villigen, 5232, Switzerland",
"organization": "Paul Scherrer Institut PSI"
}
],
"surname": "Papa",
"given_names": "A.",
"full_name": "Papa, A."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d, Piazzale A. Moro, Rome, 00185, Italy",
"organization": "INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d"
}
],
"surname": "Pettinacci",
"given_names": "V.",
"full_name": "Pettinacci, V."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Genova dell\u2019Universit\u00e0, Via Dodecaneso 33, Genoa, 16146, Italy",
"organization": "INFN Sezione di Genova dell\u2019Universit\u00e0"
}
],
"surname": "Pizzigoni",
"given_names": "G.",
"full_name": "Pizzigoni, G."
},
{
"affiliations": [
{
"country": "Russia",
"value": "Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090, Russia",
"organization": "Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences"
},
{
"country": "Russia",
"value": "Novosibirsk State University, Novosibirsk, 630090, Russia",
"organization": "Novosibirsk State University"
}
],
"surname": "Popov",
"given_names": "A.",
"full_name": "Popov, A."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d, Piazzale A. Moro, Rome, 00185, Italy",
"organization": "INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d"
}
],
"surname": "Renga",
"given_names": "F.",
"full_name": "Renga, F."
},
{
"affiliations": [
{
"country": "Switzerland",
"value": "Paul Scherrer Institut PSI, Villigen, 5232, Switzerland",
"organization": "Paul Scherrer Institut PSI"
}
],
"surname": "Ritt",
"given_names": "S.",
"full_name": "Ritt, S."
},
{
"affiliations": [
{
"country": "JINR",
"value": "Joint Institute for Nuclear Research, Dubna, 141980, Russia",
"organization": "Joint Institute for Nuclear Research"
}
],
"surname": "Rozhdestvensky",
"given_names": "A.",
"full_name": "Rozhdestvensky, A."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pavia dell\u2019Universit\u00e0, Via Bassi 6, Pavia, 27100, Italy",
"organization": "INFN Sezione di Pavia dell\u2019Universit\u00e0"
}
],
"surname": "Rossella",
"given_names": "M.",
"full_name": "Rossella, M."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Sawada",
"given_names": "R.",
"full_name": "Sawada, R."
},
{
"affiliations": [
{
"country": "Switzerland",
"value": "Paul Scherrer Institut PSI, Villigen, 5232, Switzerland",
"organization": "Paul Scherrer Institut PSI"
}
],
"surname": "Schwendimann",
"given_names": "P.",
"full_name": "Schwendimann, P."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Pisa dell\u2019Universit\u00e0, Largo B. Pontecorvo 3, Pisa, 56127, Italy",
"organization": "INFN Sezione di Pisa dell\u2019Universit\u00e0"
}
],
"surname": "Signorelli",
"given_names": "G.",
"full_name": "Signorelli, G."
},
{
"affiliations": [
{
"country": "Switzerland",
"value": "Paul Scherrer Institut PSI, Villigen, 5232, Switzerland",
"organization": "Paul Scherrer Institut PSI"
}
],
"surname": "Stoykov",
"given_names": "A.",
"full_name": "Stoykov, A."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Matematica e Fisica, INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento, Via per Arnesano, Lecce, 73100, Italy",
"organization": "INFN Sezione di Lecce dell\u2019Universit\u00e0 del Salento"
}
],
"surname": "Tassielli",
"given_names": "G.",
"full_name": "Tassielli, G."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Toyoda",
"given_names": "K.",
"full_name": "Toyoda, K."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Uchiyama",
"given_names": "Y.",
"full_name": "Uchiyama, Y."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Usami",
"given_names": "M.",
"full_name": "Usami, M."
},
{
"affiliations": [
{
"country": "Italy",
"value": "Dipartimento di Fisica, INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d, Piazzale A. Moro, Rome, 00185, Italy",
"organization": "INFN Sezione di Roma dell\u2019Universit\u00e0 \u201cSapienza\u201d"
}
],
"surname": "Voena",
"given_names": "C.",
"full_name": "Voena, C."
},
{
"affiliations": [
{
"country": "Japan",
"value": "ICEPP, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan",
"organization": "ICEPP, The University of Tokyo"
}
],
"surname": "Yanai",
"given_names": "K.",
"full_name": "Yanai, K."
},
{
"affiliations": [
{
"country": "Russia",
"value": "Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090, Russia",
"organization": "Budker Institute of Nuclear Physics of Siberian Branch of Russian Academy of Sciences"
},
{
"country": "Russia",
"value": "Novosibirsk State University, Novosibirsk, 630090, Russia",
"organization": "Novosibirsk State University"
}
],
"surname": "Yudin",
"given_names": "Yu.",
"full_name": "Yudin, Yu."
}
],
"titles": [
{
"source": "Springer",
"title": "Search for lepton flavour violating muon decay mediated by a new light particle in the MEG experiment"
}
],
"dois": [
{
"value": "10.1140/epjc/s10052-020-8364-1"
}
],
"publication_info": [
{
"page_end": "21",
"journal_title": "European Physical Journal C",
"material": "article",
"journal_volume": "80",
"artid": "s10052-020-8364-1",
"year": 2020,
"page_start": "1",
"journal_issue": "9"
}
],
"$schema": "http://repo.scoap3.org/schemas/hep.json",
"acquisition_source": {
"date": "2020-12-17T01:30:51.118360",
"source": "Springer",
"method": "Springer",
"submission_number": "ff488d363ffe11ebbd0e02163e01809a"
},
"page_nr": [
21
],
"license": [
{
"url": "https://creativecommons.org/licenses//by/4.0",
"license": "CC-BY-4.0"
}
],
"copyright": [
{
"holder": "The Author(s)",
"year": "2020"
}
],
"control_number": "57048",
"record_creation_date": "2020-09-18T02:30:20.886172",
"_files": [
{
"checksum": "md5:1ef10ebfe43054bda3bdf5e1551dfe32",
"filetype": "xml",
"bucket": "a192ec7c-9339-4350-8d25-ab2ac6203053",
"version_id": "fa8d2c7a-5372-4d53-b4c8-b6c285528886",
"key": "10.1140/epjc/s10052-020-8364-1.xml",
"size": 43617
},
{
"checksum": "md5:68c05d3c53a47987e5f191c98b0db518",
"filetype": "pdf/a",
"bucket": "a192ec7c-9339-4350-8d25-ab2ac6203053",
"version_id": "af09303e-7bf7-4522-9c17-9a4d2f021379",
"key": "10.1140/epjc/s10052-020-8364-1_a.pdf",
"size": 3747455
}
],
"collections": [
{
"primary": "European Physical Journal C"
}
],
"arxiv_eprints": [
{
"categories": [
"hep-ex"
],
"value": "2005.00339v1"
}
],
"abstracts": [
{
"source": "Springer",
"value": "We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, $$\\upmu ^+ \\rightarrow \\mathrm {e}^+\\mathrm {X}, \\mathrm {X} \\rightarrow \\upgamma \\upgamma \\ $$ <math> <mrow> <msup> <mi>\u03bc</mi> <mo>+</mo> </msup> <mo>\u2192</mo> <msup> <mrow> <mi>e</mi> </mrow> <mo>+</mo> </msup> <mi>X</mi> <mo>,</mo> <mi>X</mi> <mo>\u2192</mo> <mi>\u03b3</mi> <mi>\u03b3</mi> <mspace width=\"4pt\"></mspace> </mrow> </math> . This search uses a dataset resulting from $$7.5\\times 10^{14}$$ <math> <mrow> <mn>7.5</mn> <mo>\u00d7</mo> <msup> <mn>10</mn> <mn>14</mn> </msup> </mrow> </math> stopped muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009\u20132013. No significant excess is found in the mass region 20\u201345 MeV/c $$^2$$ <math> <msup> <mrow></mrow> <mn>2</mn> </msup> </math> for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20\u201340 MeV/c $$^2$$ <math> <msup> <mrow></mrow> <mn>2</mn> </msup> </math> , down to $${\\mathcal {O}}(10^{-11})$$ <math> <mrow> <mi>O</mi> <mo>(</mo> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>11</mn> </mrow> </msup> <mo>)</mo> </mrow> </math> at 90% confidence level."
}
],
"imprints": [
{
"date": "2020-09-17",
"publisher": "Springer"
}
]
}