Open Access

Observation of the Very Rare $Σ^{+} \to p μ^{+} μ^{-}$ Decay

R. Aaij ³⁸, A. S. W. Abdelmotteleb ⁵⁷, C. Abellan Beteta ⁵¹, F. Abudinén ⁵⁷, T. Ackernley ⁶¹, A. A. Adefisoye ⁶⁹, B. Adeva ⁴⁷, M. Adinolfi ⁵⁵, P. Adlarson ⁸⁴ et al. (LHCb Collaboration)

P. Adlarson ⁸⁴, C. Agapopoulou ¹⁴, C. A. Aidala ⁸⁶, Z. Ajaltouni¹¹, S. Akar ¹¹, K. Akiba ³⁸, P. Albicocco ²⁸, J. Albrecht ^19,b, F. Alessio ⁴⁹, Z. Aliouche ⁶³, P. Alvarez Cartelle ⁵⁶, R. Amalric ¹⁶, S. Amato ³, J. L. Amey ⁵⁵, Y. Amhis ¹⁴, L. An ⁶, L. Anderlini ²⁷, M. Andersson ⁵¹, A. Andreianov ⁴⁴, P. Andreola ⁵¹, M. Andreotti ²⁶, D. Andreou ⁶⁹, A. Anelli ^31,49,c, D. Ao ⁷, F. Archilli ^37,d, M. Argenton ²⁶, S. Arguedas Cuendis ^9,49, A. Artamonov ⁴⁴, M. Artuso ⁶⁹, E. Aslanides ¹³, R. Ataíde Da Silva ⁵⁰, M. Atzeni ⁶⁵, B. Audurier ¹², D. Bacher ⁶⁴, I. Bachiller Perea ⁵⁰, S. Bachmann ²², M. Bachmayer ⁵⁰, J. J. Back ⁵⁷, P. Baladron Rodriguez ⁴⁷, V. Balagura ¹⁵, A. Balboni ²⁶, W. Baldini ²⁶, L. Balzani ¹⁹, H. Bao ⁷, J. Baptista de Souza Leite ⁶¹, C. Barbero Pretel ^47,12, M. Barbetti ²⁷, I. R. Barbosa ⁷⁰, R. J. Barlow ⁶³, M. Barnyakov ²⁵, S. Barsuk ¹⁴, W. Barter ⁵⁹, J. Bartz ⁶⁹, S. Bashir ⁴⁰, B. Batsukh ⁵, P. B. Battista ¹⁴, A. Bay ⁵⁰, A. Beck ⁶⁵, M. Becker ¹⁹, F. Bedeschi ³⁵, I. B. Bediaga ², N. A. Behling ¹⁹, S. Belin ⁴⁷, K. Belous ⁴⁴, I. Belov ²⁹, I. Belyaev ³⁶, G. Benane ¹³, G. Bencivenni ²⁸, E. Ben-Haim ¹⁶, A. Berezhnoy ⁴⁴, R. Bernet ⁵¹, S. Bernet Andres ⁴⁶, A. Bertolin ³³, C. Betancourt ⁵¹, F. Betti ⁵⁹, J. Bex ⁵⁶, Ia. Bezshyiko ⁵¹, O. Bezshyyko ⁸⁵, J. Bhom ⁴¹, M. S. Bieker ¹⁸, N. V. Biesuz ²⁶, P. Billoir ¹⁶, A. Biolchini ³⁸, M. Birch ⁶², F. C. R. Bishop ¹⁰, A. Bitadze ⁶³, A. Bizzeti , T. Blake ⁵⁷, F. Blanc ⁵⁰, J. E. Blank ¹⁹, S. Blusk ⁶⁹, V. Bocharnikov ⁴⁴, J. A. Boelhauve ¹⁹, O. Boente Garcia ¹⁵, T. Boettcher ⁶⁸, A. Bohare ⁵⁹, A. Boldyrev ⁴⁴, C. S. Bolognani ⁸¹, R. Bolzonella ²⁶, R. B. Bonacci ¹, N. Bondar ^44,49, A. Bordelius ⁴⁹, F. Borgato ^33,49, S. Borghi ⁶³, M. Borsato ^31,c, J. T. Borsuk ⁸², E. Bottalico ⁶¹, S. A. Bouchiba ⁵⁰, M. Bovill ⁶⁴, T. J. V. Bowcock ⁶¹, A. Boyer ⁴⁹, C. Bozzi ²⁶, J. D. Brandenburg ⁸⁷, A. Brea Rodriguez ⁵⁰, N. Breer ¹⁹, J. Brodzicka ⁴¹, A. Brossa Gonzalo ^47,a, J. Brown ⁶¹, D. Brundu ³², E. Buchanan ⁵⁹, L. Buonincontri ^33,e, M. Burgos Marcos ⁸¹, A. T. Burke ⁶³, C. Burr ⁴⁹, J. S. Butter ⁵⁶, J. Buytaert ⁴⁹, W. Byczynski ⁴⁹, S. Cadeddu ³², H. Cai⁷⁴, A. Caillet ¹⁶, R. Calabrese ^26,f, S. Calderon Ramirez ⁹, L. Calefice ⁴⁵, S. Cali ²⁸, M. Calvi ^31,c, M. Calvo Gomez ⁴⁶, P. Camargo Magalhaes ^2,g, J. I. Cambon Bouzas ⁴⁷, P. Campana ²⁸, D. H. Campora Perez ⁸¹, A. F. Campoverde Quezada ⁷, S. Capelli ³¹, L. Capriotti ²⁶, R. Caravaca-Mora ⁹, A. Carbone ^25,h, L. Carcedo Salgado ⁴⁷, R. Cardinale ^29,i, A. Cardini ³², P. Carniti ^31,c, L. Carus ²², A. Casais Vidal ⁶⁵, R. Caspary ²², G. Casse ⁶¹, M. Cattaneo ⁴⁹, G. Cavallero ^26,49, V. Cavallini ^26,f, S. Celani ²², S. Cesare ^30,j, A. J. Chadwick ⁶¹, I. Chahrour ⁸⁶, H. Chang ^4,k, M. Charles ¹⁶, Ph. Charpentier ⁴⁹, E. Chatzianagnostou ³⁸, M. Chefdeville ¹⁰, C. Chen ⁵⁶, S. Chen ⁵, Z. Chen ⁷, A. Chernov ⁴¹, S. Chernyshenko ⁵³, X. Chiotopoulos ⁸¹, V. Chobanova ⁸³, M. Chrzaszcz ⁴¹, A. Chubykin ⁴⁴, V. Chulikov ^28,36, P. Ciambrone ²⁸, X. Cid Vidal ⁴⁷, G. Ciezarek ⁴⁹, P. Cifra ⁴⁹, P. E. L. Clarke ⁵⁹, M. Clemencic ⁴⁹, H. V. Cliff ⁵⁶, J. Closier ⁴⁹, C. Cocha Toapaxi ²², V. Coco ⁴⁹, J. Cogan ¹³, E. Cogneras ¹¹, L. Cojocariu ⁴³, S. Collaviti ⁵⁰, P. Collins ⁴⁹, T. Colombo ⁴⁹, M. Colonna ¹⁹, A. Comerma-Montells ⁴⁵, L. Congedo ²⁴, A. Contu ³², N. Cooke ⁶⁰, C. Coronel ⁶⁶, I. Corredoira ¹², A. Correia ¹⁶, G. Corti ⁴⁹, J. Cottee Meldrum ⁵⁵, B. Couturier ⁴⁹, D. C. Craik ⁵¹, M. Cruz Torres ^2,l, E. Curras Rivera ⁵⁰, R. Currie ⁵⁹, C. L. Da Silva ⁶⁸, S. Dadabaev ⁴⁴, L. Dai ⁷¹, X. Dai ⁴, E. Dall’Occo ⁴⁹, J. Dalseno ⁸³, C. D’Ambrosio ⁶², J. Daniel ¹¹, P. d’Argent ²⁴, G. Darze ³, A. Davidson ⁵⁷, J. E. Davies ⁶³, O. De Aguiar Francisco ⁶³, C. De Angelis ^32,m, F. De Benedetti ⁴⁹, J. de Boer ³⁸, K. De Bruyn ⁸⁰, S. De Capua ⁶³, M. De Cian ²², U. De Freitas Carneiro Da Graca ^2,n, E. De Lucia ²⁸, J. M. De Miranda ², L. De Paula ³, M. De Serio ^24,o, P. De Simone ²⁸, F. De Vellis ¹⁹, J. A. de Vries ⁸¹, F. Debernardis ²⁴, D. Decamp ¹⁰, S. Dekkers ¹, L. Del Buono ¹⁶, B. Delaney ⁶⁵, H.-P. Dembinski ¹⁹, J. Deng ⁸, V. Denysenko ⁵¹, O. Deschamps ¹¹, F. Dettori ^32,m, B. Dey ⁷⁸, P. Di Nezza ²⁸, I. Diachkov ⁴⁴, S. Didenko ⁴⁴, S. Ding ⁶⁹, L. Dittmann ²², V. Dobishuk ⁵³, A. D. Docheva ⁶⁰, C. Dong ^4,k, A. M. Donohoe ²³, F. Dordei ³², A. C. dos Reis ², A. D. Dowling ⁶⁹, W. Duan ⁷², P. Duda ⁸², M. W. Dudek ⁴¹, L. Dufour ⁴⁹, V. Duk ³⁴, P. Durante ⁴⁹, M. M. Duras ⁸², J. M. Durham ⁶⁸, O. D. Durmus ⁷⁸, A. Dziurda ⁴¹, A. Dzyuba ⁴⁴, S. Easo ⁵⁸, E. Eckstein ¹⁸, U. Egede ¹, A. Egorychev ⁴⁴, V. Egorychev ⁴⁴, S. Eisenhardt ⁵⁹, E. Ejopu ⁶³, L. Eklund ⁸⁴, M. Elashri ⁶⁶, J. Ellbracht ¹⁹, S. Ely ⁶², A. Ene ⁴³, J. Eschle ⁶⁹, S. Esen ²², T. Evans ³⁸, F. Fabiano ³², S. Faghih ⁶⁶, L. N. Falcao ², B. Fang ⁷, L. Fantini ^34,49,p, M. Faria ⁵⁰, K. Farmer ⁵⁹, D. Fazzini ^31,c, L. Felkowski ⁸², M. Feng ^5,7, M. Feo ², A. Fernandez Casani ⁴⁸, M. Fernandez Gomez ⁴⁷, A. D. Fernez ⁶⁷, F. Ferrari ^25,h, F. Ferreira Rodrigues ³, M. Ferrillo ⁵¹, M. Ferro-Luzzi ⁴⁹, S. Filippov ⁴⁴, R. A. Fini ²⁴, M. Fiorini ^26,f, M. Firlej ⁴⁰, K. L. Fischer ⁶⁴, D. S. Fitzgerald ⁸⁶, C. Fitzpatrick ⁶³, T. Fiutowski ⁴⁰, F. Fleuret ¹⁵, M. Fontana ²⁵, L. F. Foreman ⁶³, R. Forty ⁴⁹, D. Foulds-Holt ⁵⁶, V. Franco Lima ³, M. Franco Sevilla ⁶⁷, M. Frank ⁴⁹, E. Franzoso ^26,f, G. Frau ⁶³, C. Frei ⁴⁹, D. A. Friday ⁶³, J. Fu ⁷, Q. Führing ^19,56,b, Y. Fujii ¹, T. Fulghesu ¹³, E. Gabriel ³⁸, G. Galati ²⁴, M. D. Galati ³⁸, A. Gallas Torreira ⁴⁷, D. Galli ^25,h, S. Gambetta ⁵⁹, M. Gandelman ³, P. Gandini ³⁰, B. Ganie ⁶³, H. Gao ⁷, R. Gao ⁶⁴, T. Q. Gao ⁵⁶, Y. Gao ⁸, Y. Gao ⁶, Y. Gao ⁸, L. M. Garcia Martin ⁵⁰, P. Garcia Moreno ⁴⁵, J. García Pardiñas⁶⁵, P. Gardner ⁶⁷, K. G. Garg ⁸, L. Garrido ⁴⁵, C. Gaspar ⁴⁹, A. Gavrikov ³³, L. L. Gerken ¹⁹, E. Gersabeck ²⁰, M. Gersabeck ²⁰, T. Gershon ⁵⁷, S. Ghizzo ^29,i, Z. Ghorbanimoghaddam ⁵⁵, L. Giambastiani ^33,e, F. I. Giasemis ^16,q, V. Gibson ⁵⁶, H. K. Giemza ⁴², A. L. Gilman ⁶⁴, M. Giovannetti ²⁸, A. Gioventù ⁴⁵, L. Girardey ^63,58, C. Giugliano ^26,f, M. A. Giza ⁴¹, F. C. Glaser ^14,22, V. V. Gligorov ¹⁶, C. Göbel ⁷⁰, L. Golinka-Bezshyyko ⁸⁵, E. Golobardes ⁴⁶, D. Golubkov ⁴⁴, A. Golutvin ^62,49, S. Gomez Fernandez ⁴⁵, W. Gomulka ⁴⁰, F. Goncalves Abrantes ⁶⁴, M. Goncerz ⁴¹, G. Gong ^4,k, J. A. Gooding ¹⁹, I. V. Gorelov ⁴⁴, C. Gotti ³¹, E. Govorkova ⁶⁵, J. P. Grabowski ¹⁸, L. A. Granado Cardoso ⁴⁹, E. Graugés ⁴⁵, E. Graverini ^50,r, L. Grazette ⁵⁷, G. Graziani , A. T. Grecu ⁴³, L. M. Greeven ³⁸, N. A. Grieser ⁶⁶, L. Grillo ⁶⁰, S. Gromov ⁴⁴, C. Gu ¹⁵, M. Guarise ²⁶, L. Guerry ¹¹, V. Guliaeva ⁴⁴, P. A. Günther ²², A.-K. Guseinov ⁵⁰, E. Gushchin ⁴⁴, Y. Guz ^6,49, T. Gys ⁴⁹, K. Habermann ¹⁸, T. Hadavizadeh ¹, C. Hadjivasiliou ⁶⁷, G. Haefeli ⁵⁰, C. Haen ⁴⁹, G. Hallett ⁵⁷, P. M. Hamilton ⁶⁷, J. Hammerich ⁶¹, Q. Han ³³, X. Han ^22,49, S. Hansmann-Menzemer ²², L. Hao ⁷, N. Harnew ⁶⁴, T. H. Harris ¹, M. Hartmann ¹⁴, S. Hashmi ⁴⁰, J. He ^7,s, F. Hemmer ⁴⁹, C. Henderson ⁶⁶, R. D. L. Henderson ^1,57, A. M. Hennequin ⁴⁹, K. Hennessy ⁶¹, L. Henry ⁵⁰, J. Herd ⁶², P. Herrero Gascon ²², J. Heuel ¹⁷, A. Hicheur ³, G. Hijano Mendizabal ⁵¹, J. Horswill ⁶³, R. Hou ⁸, Y. Hou ¹¹, N. Howarth ⁶¹, J. Hu ⁷², W. Hu ⁷, X. Hu ^4,k, W. Hulsbergen ³⁸, R. J. Hunter ⁵⁷, M. Hushchyn ⁴⁴, D. Hutchcroft ⁶¹, M. Idzik ⁴⁰, D. Ilin ⁴⁴, P. Ilten ⁶⁶, A. Inglessi ⁴⁴, A. Iniukhin ⁴⁴, A. Ishteev ⁴⁴, K. Ivshin ⁴⁴, H. Jage ¹⁷, S. J. Jaimes Elles ^76,49,48, S. Jakobsen ⁴⁹, E. Jans ³⁸, B. K. Jashal ⁴⁸, A. Jawahery ⁶⁷, V. Jevtic ¹⁹, E. Jiang ⁶⁷, X. Jiang ^5,7, Y. Jiang ⁷, Y. J. Jiang ⁶, M. John ⁶⁴, A. John Rubesh Rajan ²³, D. Johnson ⁵⁴, C. R. Jones ⁵⁶, T. P. Jones ⁵⁷, S. Joshi ⁴², B. Jost ⁴⁹, J. Juan Castella ⁵⁶, N. Jurik ⁴⁹, I. Juszczak ⁴¹, D. Kaminaris ⁵⁰, S. Kandybei ⁵², M. Kane ⁵⁹, Y. Kang ^4,k, C. Kar ¹¹, M. Karacson ⁴⁹, D. Karpenkov ⁴⁴, A. Kauniskangas ⁵⁰, J. W. Kautz ⁶⁶, M. K. Kazanecki ⁴¹, F. Keizer ⁴⁹, M. Kenzie ⁵⁶, T. Ketel ³⁸, B. Khanji ⁶⁹, A. Kharisova ⁴⁴, S. Kholodenko ^35,49, G. Khreich ¹⁴, T. Kirn ¹⁷, V. S. Kirsebom ^31,c, O. Kitouni ⁶⁵, S. Klaver ³⁹, N. Kleijne ^35,t, K. Klimaszewski ⁴², M. R. Kmiec ⁴², S. Koliiev ⁵³, L. Kolk ¹⁹, A. Konoplyannikov ⁶, P. Kopciewicz ⁴⁹, P. Koppenburg ³⁸, A. Korchin ⁵², M. Korolev ⁴⁴, I. Kostiuk ³⁸, O. Kot ⁵³, S. Kotriakhova , A. Kozachuk ⁴⁴, P. Kravchenko ⁴⁴, L. Kravchuk ⁴⁴, M. Kreps ⁵⁷, P. Krokovny ⁴⁴, W. Krupa ⁶⁹, W. Krzemien ⁴², O. Kshyvanskyi ⁵³, S. Kubis ⁸², M. Kucharczyk ⁴¹, V. Kudryavtsev ⁴⁴, E. Kulikova ⁴⁴, A. Kupsc ⁸⁴, V. Kushnir ⁵², B. Kutsenko ¹³, I. Kyryllin ⁵², D. Lacarrere ⁴⁹, P. Laguarta Gonzalez ⁴⁵, A. Lai ³², A. Lampis ³², D. Lancierini ⁶², C. Landesa Gomez ⁴⁷, J. J. Lane ¹, G. Lanfranchi ²⁸, C. Langenbruch ²², J. Langer ¹⁹, O. Lantwin ⁴⁴, T. Latham ⁵⁷, F. Lazzari ^35,49,r, C. Lazzeroni ⁵⁴, R. Le Gac ¹³, H. Lee ⁶¹, R. Lefèvre ¹¹, A. Leflat ⁴⁴, S. Legotin ⁴⁴, M. Lehuraux ⁵⁷, E. Lemos Cid ⁴⁹, O. Leroy ¹³, T. Lesiak ⁴¹, E. D. Lesser ⁴⁹, B. Leverington ²², A. Li ^4,k, C. Li ⁴, C. Li ¹³, H. Li ⁷², J. Li ⁸, K. Li ⁷⁵, L. Li ⁶³, M. Li ⁸, P. Li ⁷, P.-R. Li ⁷³, Q. Li ^5,7, S. Li ⁸, T. Li ⁷¹, T. Li ⁷², Y. Li ⁸, Y. Li ⁵, Z. Lian ^4,k, X. Liang ⁶⁹, S. Libralon ⁴⁸, C. Lin ⁷, T. Lin ⁵⁸, R. Lindner ⁴⁹, H. Linton ⁶², V. Lisovskyi ⁵⁰, R. Litvinov ^32,49, D. Liu ⁸, F. L. Liu ¹, G. Liu ⁷², K. Liu ⁷³, S. Liu ^5,7, W. Liu ⁸, Y. Liu ⁵⁹, Y. Liu ⁷³, Y. L. Liu ⁶², G. Loachamin Ordonez ⁷⁰, A. Lobo Salvia ⁴⁵, A. Loi ³², T. Long ⁵⁶, J. H. Lopes ³, A. Lopez Huertas ⁴⁵, S. López Soliño ⁴⁷, Q. Lu ¹⁵, C. Lucarelli ^27,u, D. Lucchesi ^33,e, M. Lucio Martinez ⁴⁸, Y. Luo ⁶, A. Lupato ^33,v, E. Luppi ^26,f, K. Lynch ²³, X.-R. Lyu ⁷, G. M. Ma ^4,k, S. Maccolini ¹⁹, F. Machefert ¹⁴, F. Maciuc ⁴³, B. Mack ⁶⁹, I. Mackay ⁶⁴, L. M. Mackey ⁶⁹, L. R. Madhan Mohan ⁵⁶, M. J. Madurai ⁵⁴, D. Magdalinski ³⁸, D. Maisuzenko ⁴⁴, J. J. Malczewski ⁴¹, S. Malde ⁶⁴, L. Malentacca ⁴⁹, A. Malinin ⁴⁴, T. Maltsev ⁴⁴, G. Manca ^32,m, G. Mancinelli ¹³, C. Mancuso ¹⁴, R. Manera Escalero ⁴⁵, F. M. Manganella ³⁷, D. Manuzzi ²⁵, D. Marangotto ³⁰, J. F. Marchand ¹⁰, R. Marchevski ⁵⁰, U. Marconi ²⁵, E. Mariani ¹⁶, S. Mariani ⁴⁹, C. Marin Benito ⁴⁵, J. Marks ²², A. M. Marshall ⁵⁵, L. Martel ⁶⁴, G. Martelli ^34,p, G. Martellotti ³⁶, L. Martinazzoli ⁴⁹, M. Martinelli ^31,c, D. Martinez Gomez ⁸⁰, D. Martinez Santos ⁸³, F. Martinez Vidal ⁴⁸, A. Martorell i Granollers ⁴⁶, A. Massafferri ², R. Matev ⁴⁹, A. Mathad ⁴⁹, V. Matiunin ⁴⁴, C. Matteuzzi ⁶⁹, K. R. Mattioli ¹⁵, A. Mauri ⁶², E. Maurice ¹⁵, J. Mauricio ⁴⁵, P. Mayencourt ⁵⁰, J. Mazorra de Cos ⁴⁸, M. Mazurek ⁴², M. McCann ⁶², T. H. McGrath ⁶³, N. T. McHugh ⁶⁰, A. McNab ⁶³, R. McNulty ²³, B. Meadows ⁶⁶, G. Meier ¹⁹, D. Melnychuk ⁴², F. M. Meng ^4,k, M. Merk ^38,81, A. Merli ⁵⁰, L. Meyer Garcia ⁶⁷, D. Miao ^5,7, H. Miao ⁷, M. Mikhasenko ⁷⁷, D. A. Milanes ^76,w, A. Minotti ^31,c, E. Minucci ²⁸, T. Miralles ¹¹, B. Mitreska ¹⁹, D. S. Mitzel ¹⁹, A. Modak ⁵⁸, L. Moeser ¹⁹, R. A. Mohammed ⁶⁴, R. D. Moise ¹⁷, E. F. Molina Cardenas ⁸⁶, T. Mombächer ⁴⁹, M. Monk ^57,1, S. Monteil ¹¹, A. Morcillo Gomez ⁴⁷, G. Morello ²⁸, M. J. Morello ^35,t, M. P. Morgenthaler ²², J. Moron ⁴⁰, W. Morren ³⁸, A. B. Morris ⁴⁹, A. G. Morris ¹³, R. Mountain ⁶⁹, H. Mu ^4,k, Z. M. Mu ⁶, E. Muhammad ⁵⁷, F. Muheim ⁵⁹, M. Mulder ⁸⁰, K. Müller ⁵¹, F. Muñoz-Rojas ⁹, R. Murta ⁶², V. Mytrochenko ⁵², P. Naik ⁶¹, T. Nakada ⁵⁰, R. Nandakumar ⁵⁸, T. Nanut ⁴⁹, I. Nasteva ³, M. Needham ⁵⁹, E. Nekrasova ⁴⁴, N. Neri ^30,j, S. Neubert ¹⁸, N. Neufeld ⁴⁹, P. Neustroev⁴⁴, J. Nicolini ⁴⁹, D. Nicotra ⁸¹, E. M. Niel ⁴⁹, N. Nikitin ⁴⁴, Q. Niu⁷³, P. Nogarolli ³, P. Nogga ¹⁸, C. Normand ⁵⁵, J. Novoa Fernandez ⁴⁷, G. Nowak ⁶⁶, C. Nunez ⁸⁶, H. N. Nur ⁶⁰, A. Oblakowska-Mucha ⁴⁰, V. Obraztsov ⁴⁴, T. Oeser ¹⁷, S. Okamura ^26,f, A. Okhotnikov⁴⁴, O. Okhrimenko ⁵³, R. Oldeman ^32,m, F. Oliva ⁵⁹, M. Olocco ¹⁹, C. J. G. Onderwater ⁸¹, R. H. O’Neil ⁴⁹, D. Osthues ¹⁹, J. M. Otalora Goicochea ³, P. Owen ⁵¹, A. Oyanguren ⁴⁸, O. Ozcelik ⁵⁹, F. Paciolla ^35,x, A. Padee ⁴², K. O. Padeken ¹⁸, B. Pagare ⁵⁷, T. Pajero ⁴⁹, A. Palano ²⁴, M. Palutan ²⁸, X. 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Sagidova ⁴⁴, D. Sahoo ⁷⁸, N. Sahoo ⁵⁴, B. Saitta ^32,m, M. Salomoni ^31,49,c, I. Sanderswood ⁴⁸, R. Santacesaria ³⁶, C. Santamarina Rios ⁴⁷, M. Santimaria ²⁸, L. Santoro ², E. Santovetti ³⁷, A. Saputi ^26,49, D. Saranin ⁴⁴, A. Sarnatskiy ⁸⁰, G. Sarpis ⁵⁹, M. Sarpis ⁷⁹, C. Satriano ^36,y, A. Satta ³⁷, M. Saur ⁷³, D. Savrina ⁴⁴, H. Sazak ¹⁷, F. Sborzacchi ^49,28, A. Scarabotto ¹⁹, S. Schael ¹⁷, S. Scherl ⁶¹, M. Schiller ⁶⁰, H. Schindler ⁴⁹, M. Schmelling ²¹, B. Schmidt ⁴⁹, S. Schmitt ¹⁷, H. Schmitz¹⁸, O. Schneider ⁵⁰, A. Schopper ⁶², N. Schulte ¹⁹, S. Schulte ⁵⁰, M. H. Schune ¹⁴, G. Schwering ¹⁷, B. Sciascia ²⁸, A. Sciuccati ⁴⁹, I. Segal ⁷⁷, S. Sellam ⁴⁷, A. Semennikov ⁴⁴, T. Senger ⁵¹, M. Senghi Soares ³⁹, A. Sergi ^29,i, N. Serra ⁵¹, L. Sestini ²⁷, A. Seuthe ¹⁹, B. Sevilla Sanjuan ⁴⁶, Y. Shang ⁶, D. M. Shangase ⁸⁶, M. Shapkin ⁴⁴, R. S. Sharma ⁶⁹, I. Shchemerov ⁴⁴, L. Shchutska ⁵⁰, T. Shears ⁶¹, L. Shekhtman ⁴⁴, Z. Shen ³⁸, S. Sheng ^5,7, V. Shevchenko ⁴⁴, B. Shi ⁷, Q. Shi ⁷, Y. Shimizu ¹⁴, E. Shmanin ²⁵, R. Shorkin ⁴⁴, J. D. Shupperd ⁶⁹, R. Silva Coutinho ⁶⁹, G. Simi ^33,e, S. Simone ^24,o, M. Singha ⁷⁸, N. Skidmore ⁵⁷, T. Skwarnicki ⁶⁹, M. W. Slater ⁵⁴, E. Smith ⁶⁵, K. Smith ⁶⁸, M. Smith ⁶², L. Soares Lavra ⁵⁹, M. D. Sokoloff ⁶⁶, F. J. P. Soler ⁶⁰, A. Solomin ⁵⁵, A. Solovev ⁴⁴, I. Solovyev ⁴⁴, N. S. Sommerfeld ¹⁸, R. Song ¹, Y. Song ⁵⁰, Y. Song ^4,k, Y. S. Song ⁶, F. L. Souza De Almeida ⁶⁹, B. Souza De Paula ³, E. Spadaro Norella ^29,i, E. Spedicato ²⁵, J. G. Speer ¹⁹, E. Spiridenkov⁴⁴, P. Spradlin ⁶⁰, V. Sriskaran ⁴⁹, F. Stagni ⁴⁹, M. Stahl ⁷⁷, S. Stahl ⁴⁹, S. Stanislaus ⁶⁴, M. Stefaniak ⁸⁷, E. N. Stein ⁴⁹, O. Steinkamp ⁵¹, O. Stenyakin⁴⁴, H. Stevens ¹⁹, D. Strekalina ⁴⁴, Y. Su ⁷, F. Suljik ⁶⁴, J. Sun ³², L. Sun ⁷⁴, D. Sundfeld ², W. Sutcliffe ⁵¹, K. Swientek ⁴⁰, F. Swystun ⁵⁶, A. Szabelski ⁴², T. Szumlak ⁴⁰, Y. Tan ^4,k, Y. Tang ⁷⁴, Y. T. Tang ⁷, M. D. Tat ²², A. Terentev ⁴⁴, F. Terzuoli ^35,49,x, F. Teubert ⁴⁹, U. Thoma ¹⁸, E. Thomas ⁴⁹, D. J. D. Thompson ⁵⁴, H. Tilquin ⁶², V. Tisserand ¹¹, S. T’Jampens ¹⁰, M. Tobin ⁵, L. Tomassetti ^26,f, G. Tonani ^30,j, X. Tong ⁶, T. Tork ³⁰, D. Torres Machado ², L. Toscano ¹⁹, D. Y. Tou ^4,k, C. Trippl ⁴⁶, G. Tuci ²², N. Tuning ³⁸, L. H. Uecker ²², A. Ukleja ⁴⁰, D. J. Unverzagt ²², A. Upadhyay ⁷⁸, B. Urbach ⁵⁹, A. Usachov ³⁹, A. Ustyuzhanin ⁴⁴, U. Uwer ²², V. Vagnoni ²⁵, V. Valcarce Cadenas ⁴⁷, G. Valenti ²⁵, N. Valls Canudas ⁴⁹, J. van Eldik ⁴⁹, H. Van Hecke ⁶⁸, E. van Herwijnen ⁶², C. B. Van Hulse ^47,z, R. Van Laak ⁵⁰, M. van Veghel ³⁸, G. Vasquez ⁵¹, R. Vazquez Gomez ⁴⁵, P. Vazquez Regueiro ⁴⁷, C. Vázquez Sierra ⁸³, S. Vecchi ²⁶, J. J. Velthuis ⁵⁵, M. Veltri ^27,aa, A. Venkateswaran ⁵⁰, M. Verdoglia ³², M. Vesterinen ⁵⁷, D. Vico Benet ⁶⁴, P. Vidrier Villalba ⁴⁵, M. Vieites Diaz ⁴⁷, X. Vilasis-Cardona ⁴⁶, E. Vilella Figueras ⁶¹, A. Villa ²⁵, P. Vincent ¹⁶, B. Vivacqua ³, F. C. Volle ⁵⁴, D. vom Bruch ¹³, N. Voropaev ⁴⁴, K. Vos ⁸¹, C. Vrahas ⁵⁹, J. Wagner ¹⁹, J. Walsh ³⁵, E. J. Walton ^1,57, G. Wan ⁶, A. Wang ⁷, C. Wang ²², G. Wang ⁸, H. Wang ⁷³, J. Wang ⁶, J. Wang ⁵, J. Wang ^4,k, J. Wang ⁷⁴, M. Wang ⁴⁹, N. W. Wang ⁷, R. Wang ⁵⁵, X. Wang ⁸, X. Wang ⁷², X. W. Wang ⁶², Y. Wang ⁷⁵, Y. Wang ⁶, Y. W. Wang ⁷³, Z. Wang ¹⁴, Z. Wang ^4,k, Z. Wang ³⁰, J. A. Ward ^57,1, M. Waterlaat ⁴⁹, N. K. Watson ⁵⁴, D. Websdale ⁶², Y. Wei ⁶, J. Wendel ⁸³, B. D. C. Westhenry ⁵⁵, C. White ⁵⁶, M. Whitehead ⁶⁰, E. Whiter ⁵⁴, A. R. Wiederhold ⁶³, D. Wiedner ¹⁹, G. Wilkinson ^64,49, M. K. Wilkinson ⁶⁶, M. Williams ⁶⁵, M. J. Williams ⁴⁹, M. R. J. Williams ⁵⁹, R. Williams ⁵⁶, Z. Williams ⁵⁵, F. F. Wilson ⁵⁸, M. Winn ¹², W. Wislicki ⁴², M. Witek ⁴¹, L. Witola ¹⁹, G. Wormser ¹⁴, S. A. Wotton ⁵⁶, H. Wu ⁶⁹, J. Wu ⁸, X. Wu ⁷⁴, Y. Wu ^6,56, Z. Wu ⁷, K. Wyllie ⁴⁹, S. Xian ⁷², Z. Xiang ⁵, Y. Xie ⁸, T. X. Xing ³⁰, A. Xu ³⁵, L. Xu ^4,k, L. Xu ^4,k, M. Xu ⁵⁷, Z. Xu ⁴⁹, Z. Xu ⁷, Z. Xu ⁵, K. Yang ⁶², X. Yang ⁶, Y. Yang ^29,i, Z. Yang ⁶, V. Yeroshenko ¹⁴, H. Yeung ⁶³, H. Yin ⁸, X. Yin ⁷, C. Y. Yu ⁶, J. Yu ⁷¹, X. Yuan ⁵, Y Yuan ^5,7, E. Zaffaroni ⁵⁰, M. Zavertyaev ²¹, M. Zdybal ⁴¹, F. Zenesini ²⁵, C. Zeng ^5,7, M. Zeng ^4,k, C. Zhang ⁶, D. Zhang ⁸, J. Zhang ⁷, L. Zhang ^4,k, R. Zhang ⁸, S. Zhang ⁷¹, S. Zhang ⁶⁴, Y. Zhang ⁶, Y. Z. Zhang ^4,k, Z. Zhang ^4,k, Y. Zhao ²², A. Zhelezov ²², S. Z. Zheng ⁶, X. Z. Zheng ^4,k, Y. Zheng ⁷, T. Zhou ⁶, X. Zhou ⁸, Y. Zhou ⁷, V. Zhovkovska ⁵⁷, L. Z. Zhu ⁷, X. Zhu ^4,k, X. Zhu ⁸, Y. Zhu ¹⁷, V. Zhukov ¹⁷, J. Zhuo ⁴⁸, Q. Zou ^5,7, D. Zuliani ^33,e, and G. Zunica ⁵⁰ (LHCb Collaboration)

¹School of Physics and Astronomy, Monash University, Melbourne, Australia
²Centro Brasileiro de Pesquisas Físicas (CBPF), Rio de Janeiro, Brazil
³Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
⁴Department of Engineering Physics, Tsinghua University, Beijing, China
⁵Institute Of High Energy Physics (IHEP), Beijing, China
⁶School of Physics State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China
⁷University of Chinese Academy of Sciences, Beijing, China
⁸Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China
⁹Consejo Nacional de Rectores (CONARE), San Jose, Costa Rica
¹⁰Université Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France
¹¹Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France
¹²Université Paris-Saclay, Centre d’Etudes de Saclay (CEA), IRFU, Saclay, France, Gif-Sur-Yvette, France
¹³Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France
¹⁴Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
¹⁵Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
¹⁶LPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3, Paris, France
¹⁷I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany
¹⁸Universität Bonn - Helmholtz-Institut für Strahlen und Kernphysik, Bonn, Germany
¹⁹Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany
²⁰Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
²¹Max-Planck-Institut für Kernphysik (MPIK), Heidelberg, Germany
²²Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
²³School of Physics, University College Dublin, Dublin, Ireland
²⁴INFN Sezione di Bari, Bari, Italy
²⁵INFN Sezione di Bologna, Bologna, Italy
²⁶INFN Sezione di Ferrara, Ferrara, Italy
²⁷INFN Sezione di Firenze, Firenze, Italy
²⁸INFN Laboratori Nazionali di Frascati, Frascati, Italy
²⁹INFN Sezione di Genova, Genova, Italy
³⁰INFN Sezione di Milano, Milano, Italy
³¹INFN Sezione di Milano-Bicocca, Milano, Italy
³²INFN Sezione di Cagliari, Monserrato, Italy
³³INFN Sezione di Padova, Padova, Italy
³⁴INFN Sezione di Perugia, Perugia, Italy
³⁵INFN Sezione di Pisa, Pisa, Italy
³⁶INFN Sezione di Roma La Sapienza, Roma, Italy
³⁷INFN Sezione di Roma Tor Vergata, Roma, Italy
³⁸Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands
³⁹Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, Netherlands
⁴⁰AGH - University of Krakow, Faculty of Physics and Applied Computer Science, Kraków, Poland
⁴¹Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland
⁴²National Center for Nuclear Research (NCBJ), Warsaw, Poland
⁴³Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania
⁴⁴Authors affiliated with an institute formerly covered by a cooperation agreement with CERN
⁴⁵ICCUB, Universitat de Barcelona, Barcelona, Spain
⁴⁶La Salle, Universitat Ramon Llull, Barcelona, Spain
⁴⁷Instituto Galego de Física de Altas Enerxías (IGFAE), Universidade de Santiago de Compostela, Santiago de Compostela, Spain
⁴⁸Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia - CSIC, Valencia, Spain
⁴⁹European Organization for Nuclear Research (CERN), Geneva, Switzerland
⁵⁰Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
⁵¹Physik-Institut, Universität Zürich, Zürich, Switzerland
⁵²NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine
⁵³Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine
⁵⁴School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom
⁵⁵H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom
⁵⁶Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
⁵⁷Department of Physics, University of Warwick, Coventry, United Kingdom
⁵⁸STFC Rutherford Appleton Laboratory, Didcot, United Kingdom
⁵⁹School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
⁶⁰School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom
⁶¹Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom
⁶²Imperial College London, London, United Kingdom
⁶³Department of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
⁶⁴Department of Physics, University of Oxford, Oxford, United Kingdom
⁶⁵Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
⁶⁶University of Cincinnati, Cincinnati, Ohio, USA
⁶⁷University of Maryland, College Park, Maryland, USA
⁶⁸Los Alamos National Laboratory (LANL), Los Alamos, New Mexico, USA
⁶⁹Syracuse University, Syracuse, New York, USA
⁷⁰Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil (associated with Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil)
⁷¹School of Physics and Electronics, Hunan University, Changsha City, China (associated with Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China)
⁷²Guangdong Provincial Key Laboratory of Nuclear Science, Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Institute of Quantum Matter, South China Normal University, Guangzhou, China (associated with Department of Engineering Physics, Tsinghua University, Beijing, China)
⁷³Lanzhou University, Lanzhou, China (associated with Institute Of High Energy Physics (IHEP), Beijing, China)
⁷⁴School of Physics and Technology, Wuhan University, Wuhan, China (associated with Department of Engineering Physics, Tsinghua University, Beijing, China)
⁷⁵Henan Normal University, Xinxiang, China (associated with Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China)
⁷⁶Departamento de Fisica, Universidad Nacional de Colombia, Bogota, Colombia (associated with LPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3, Paris, France)
⁷⁷Ruhr Universitaet Bochum, Fakultaet f. Physik und Astronomie, Bochum, Germany (associated with Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany)
⁷⁸Eotvos Lorand University, Budapest, Hungary (associated with European Organization for Nuclear Research (CERN), Geneva, Switzerland)
⁷⁹Faculty of Physics, Vilnius University, Vilnius, Lithuania (associated with Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany)
⁸⁰Van Swinderen Institute, University of Groningen, Groningen, Netherlands (associated with Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands)
⁸¹Universiteit Maastricht, Maastricht, Netherlands (associated with Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands)
⁸²Tadeusz Kosciuszko Cracow University of Technology, Cracow, Poland (associated with Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland)
⁸³Universidade da Coruña, A Coruña, Spain (associated with La Salle, Universitat Ramon Llull, Barcelona, Spain)
⁸⁴Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden (associated with School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom)
⁸⁵Taras Schevchenko University of Kyiv, Faculty of Physics, Kyiv, Ukraine (associated with Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France)
⁸⁶University of Michigan, Ann Arbor, Michigan, USA (associated with Syracuse University, Syracuse, New York, USA)
⁸⁷Ohio State University, Columbus, USA (associated with Los Alamos National Laboratory (LANL), Los Alamos, New Mexico, USA)

^*Full author list given at the end of the Letter.
^aDeceased.
^bAlso at Lamarr Institute for Machine Learning and Artificial Intelligence, Dortmund, Germany.
^cAlso at Università degli Studi di Milano-Bicocca, Milano, Italy.
^dAlso at Università di Roma Tor Vergata, Roma, Italy.
^eAlso at Università di Padova, Padova, Italy.
^fAlso at Università di Ferrara, Ferrara, Italy.
^gAlso at Facultad de Ciencias Fisicas, Madrid, Spain.
^hAlso at Università di Bologna, Bologna, Italy.
ⁱAlso at Università di Genova, Genova, Italy.
^jAlso at Università degli Studi di Milano, Milano, Italy.
^kAlso at Center for High Energy Physics, Tsinghua University, Beijing, China.
^lAlso at Universidad Nacional Autónoma de Honduras, Tegucigalpa, Honduras.
^mAlso at Università di Cagliari, Cagliari, Italy.
ⁿAlso at Centro Federal de Educacão Tecnológica Celso Suckow da Fonseca, Rio De Janeiro, Brazil.
^oAlso at Università di Bari, Bari, Italy.
^pAlso at Università di Perugia, Perugia, Italy.
^qAlso at LIP6, Sorbonne Université, Paris, France.
^rAlso at Università di Pisa, Pisa, Italy.
^sAlso at Hangzhou Institute for Advanced Study, UCAS, Hangzhou, China.
^tAlso at Scuola Normale Superiore, Pisa, Italy.
^uAlso at Università di Firenze, Firenze, Italy.
^vAlso at Università di Bergamo, Bergamo, Italy.
^wAlso at Universidad de Ingeniería y Tecnología (UTEC), Lima, Peru.
^xAlso at Università di Siena, Siena, Italy.
^yAlso at Università della Basilicata, Potenza, Italy.
^zAlso at Universidad de Alcalá, Alcalá de Henares, Spain.
^aaAlso at Università di Urbino, Urbino, Italy.

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Phys. Rev. Lett. 135, 051801 – Published 29 July, 2025

DOI: https://doi.org/10.1103/r3v2-kmmp

Abstract

The first observation of the $Σ^{+} \to p μ^{+} μ^{-}$ decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of $5.4 {fb}^{- 1}$ , collected with the LHCb detector at a center-of-mass energy of 13 TeV. A yield of $237 \pm 16 Σ^{+} \to p μ^{+} μ^{-}$ decays is obtained, where the uncertainty is statistical only. A branching fraction of $(1.08 \pm 0.17) \times 10^{- 8}$ is measured, where the uncertainty includes statistical and systematic sources. No evidence of resonant structures is found in the dimuon invariant-mass distribution. All results are compatible with standard model expectations. This represents the rarest decay of a baryon ever observed.

Physics Subject Headings (PhySH)

Article Text

Supplemental Material

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http://cds.cern.ch/record/2929686

Phys. Rev. Lett. 135, 051801– Published 29 July, 2025

Vol. 135, Iss. 5 — 1 August 2025

Received 9 April 2025
Accepted 2 June 2025

DOI: https://doi.org/10.1103/r3v2-kmmp

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Observation of the Very Rare $Σ^{+} \to p μ^{+} μ^{-}$ Decay

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Observation of the Very Rare Σ+→pμ+μ− Decay

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Observation of the Very Rare $Σ^{+} \to p μ^{+} μ^{-}$ Decay