Test of lepton universality in beauty-quark decays (2024)

Data availability

LHCb data used in this analysis will be released according to the LHCb external data access policy, which can be downloaded from http://opendata.cern.ch/record/410/files/LHCb-Data-Policy.pdf. The raw data in all of the figures of this paper, and additional supplementary material, can be downloaded from https://cds.cern.ch/record/2758740, where no access codes are required. In addition, the likelihood profile shown in Extended Data Fig. 4 has been added to the HEPData platform at https://www.hepdata.net/record/ins1852846?version=1.

Code availability

LHCb software used to process the data analysed in this paper is available at https://gitlab.cern.ch/lhcb.

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Machine finds tantalising hints of new physics
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Acknowledgements

We thank our colleagues in the CERN accelerator departments for the excellent performance of the LHC, and the technical and administrative staff at the LHCb institutes. We acknowledge support from CERN and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST and NSFC (China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN (Italy); NWO (Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MSHE (Russia); MICINN (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); DOE NP and NSF (United States). We acknowledge the computing resources that are provided by CERN, IN2P3 (France), KIT and DESY (Germany), INFN (Italy), SURF (the Netherlands), PIC (Spain), GridPP (United Kingdom), RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH (Romania), CBPF (Brazil), PL-GRID (Poland) and NERSC (United States). We are indebted to the communities behind the multiple open-source software packages on which we depend. Individual groups or members have received support from ARC and ARDC (Australia); AvH Foundation (Germany); EPLANET, Marie Skłodowska-Curie Actions and ERC (European Union); A*MIDEX, ANR, Labex P2IO and OCEVU, and Région Auvergne-Rhône-Alpes (France); Key Research Program of Frontier Sciences of CAS, CAS PIFI, CAS CCEPP, Fundamental Research Funds for the Central Universities, and Sci. & Tech. Program of Guangzhou (China); RFBR, RSF and Yandex LLC (Russia); GVA, XuntaGal and GENCAT (Spain); the Leverhulme Trust, the Royal Society and UKRI (United Kingdom).

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Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands
R. Aaij,J. S. Butter,K. Carvalho Akiba,S. Ferreres Sole,E. Gabriel,R. E. Geertsema,L. M. Greeven,K. Heijhoff,W. Hulsbergen,D. Hynds,E. Jans,S. Klaver,P. Koppenburg,I. Kostiuk,H. S. Kuindersma,M. Lucio Martinez,V. Lukashenko,A. Mauri,M. Merk,A. Pellegrino,C. Sanchez Gras,M. Schubiger,A. Snoch,N. Tuning,A. Usachov,M. van Beuzekom&M. Veronesi
Physik-Institut, Universität Zürich, Zürich, Switzerland
C. Abellán Beteta,M. Atzeni,R. Bernet,C. Betancourt,Ia. Bezshyiko,A. Buonaura,D. De Simone,V. Denysenko,J. Eschle,M. Ferrillo,D. Lancierini,O. Lantwin,A. Mathad,K. Müller,P. Owen,N. Serra,R. Silva Coutinho,O. Steinkamp&Z. Wang
Oliver Lodge Laboratory, University of Liverpool, Liverpool, UK
T. Ackernley,T. J. V. Bowco*ck,G. Casse,A. J. Chadwick,C. A. Chavez Barajas,K. Dreimanis,S. Farry,V. Franco Lima,T. Halewood-leagas,J. P. Hammerich,T. Harrison,K. Hennessy,D. Hutchcroft,P. J. Marshall,J. V. Mead,K. Rinnert,E. Rodrigues,T. Shears,K. A. Thomson,E. Vilella Figueras,H. M. Wark&L. E. Yeomans
Instituto Galego de Física de Altas Enerxías (IGFAE), Universidade de Santiago de Compostela, Santiago de Compostela, Spain
B. Adeva,P. Baladron Rodriguez,O. Boente Garcia,A. Brea Rodriguez,A. Casais Vidal,V. Chobanova,X. Cid Vidal,J. Dalseno,L. Dieste Maronas,A. Fernandez Prieto,A. Gallas Torreira,B. Garcia Plana,A. Gioventù,J. Lomba Castro,D. Martinez Santos,C. J. Parkinson,M. Plo Casasus,C. Prouve,M. Romero Lamas,A. Romero Vidal,J. J. Saborido Silva,C. Santamarina Rios,S. Sellam,R. Vazquez Gomez&P. Vazquez Regueiro
H.H. Wills Physics Laboratory, University of Bristol, Bristol, UK
M. Adinolfi,S. Bhasin,P. Camargo Magalhaes,M. G. Chapman,R. Lane,S. Maddrell-Mander,L. R. Madhan Mohan,A. M. Marshall,P. Naik,D. P. O’Hanlon,K. Petridis,G. J. Pomery,J. H. Rademacker,J. J. Velthuis,R. Wang,B. D. C. Westhenry&M. Whitehead
Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, MI, France
H. Afsharnia,Z. Ajaltouni,E. Cogneras,O. Deschamps,R. Lefèvre,J. Maratas,S. Monteil,P. Perret,D. Popov,H. Sazak,L. Soares Lavra&V. Tisserand
University of Michigan, Ann Arbor, USA
C. A. Aidala,D. S. Fitzgerald,S. H. Lee,K. R. Mattioli,C. Nunez,J. D. Roth&D. M. Shangase
INFN Sezione di Milano, Milano, Italy
S. Aiola,J. Fu,P. Gandini,L. Henry,D. Marangotto,A. Merli,N. Neri,M. Petruzzo&E. Spadaro Norella
University of Cincinnati, Cincinnati, OH, USA
S. Akar,P. Ilten,B. Meadows,C. Pappenheimer,M. D. Sokoloff,M. Stahl&D. Vieira
Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany
J. Albrecht,A. Battig,M. Becker,M. S. Bieker,J. A. Boelhauve,L. Calefice,E. Dall’Occo,H.-P. Dembinski,Q. Fuehring,L. L. Gerken,K. Heinicke,S. E. Hollitt,P. Ibis,V. Jevtic,B. Khanji,J. Langer,V. Lisovskyi,P. Mackowiak,G. Meier,A. Mödden,T. Mombächer,N. S. Nolte,M. Saur,M. Schellenberg,A. Seuthe,B. Spaan,H. Stevens&D. Wiedner
European Organization for Nuclear Research (CERN), Geneva, Switzerland
F. Alessio,L. An,C. Bertella,F. Betti,M. P. Blago,N. Bondar,A. Boyer,M. Brodski,C. Burr,J. Buytaert,W. Byczynski,M. Cattaneo,G. Cavallero,Ph. Charpentier,G. Ciezarek,M. Clemencic,J. Closier,V. Coco,P. Collins,T. Colombo,G. Corti,B. Couturier,C. D’Ambrosio,P. d’Argent,H. Dijkstra,L. Dufour,P. Durante,T. Evans,M. Féo,M. Ferro-Luzzi,R. Forty,M. Frank,C. Frei,W. Funk,S. Gambetta,C. Gaspar,C. Giugliano,E. L. Gkougkousis,E. Govorkova,L. A. Granado Cardoso,T. Gys,C. Haen,J. Haimberger,C. Hasse,M. Hatch,A. M. Hennequin,R. Jacobsson,S. Jakobsen,D. Johnson,B. Jost,N. Jurik,M. Karacson,F. Keizer,R. D. Krawczyk,D. Lacarrere,R. Lindner,B. Malecki,C. Marin Benito,L. Martinazzoli,R. Matev,Z. Mathe,M. Mazurek,M. Mikhasenko,M. Milovanovic,D. S. Mitzel,F. Muheim,M. Mulder,D. Müller,P. Muzzetto,N. Neufeld,P. R. Pais,A. Pearce,M. Pepe Altarelli,M. Petric,F. Pisani,S. Ponce,D. Popov,L. Promberger,P. Roloff,T. Ruf,M. Salomoni,H. Schindler,B. Schmidt,A. Schopper,R. Schwemmer,P. Seyfert,F. Stagni,S. Stahl,M. Szymanski,F. Teubert,E. Thomas,N. Tuning,A. Valassi,C. Vázquez Sierra,K. Wyllie&O. Zenaiev
School of Physics and Astronomy, University of Glasgow, Glasgow, UK
M. Alexander,D. Bobulska,G. Coombs,L. Douglas,L. Eklund,D. A. Friday,I. Longstaff,M. Petric,G. Sarpis,M. Schiller,F. J. P. Soler&P. Spradlin
ICCUB, Universitat de Barcelona, Barcelona, Spain
A. Alfonso Albero,A. Camboni,J. M. Fernandez-tenllado Arribas,P. Garcia Moreno,L. Garrido,P. Gironella Gironell,S. Gomez Fernandez,E. Graugés,J. Mauricio&D. Sanchez Gonzalo
Department of Physics and Astronomy, University of Manchester, Manchester, UK
Z. Aliouche,R. J. Barlow,A. Bitadze,S. Borghi,J. L. Cobbledick,A. Davis,O. De Aguiar Francisco,S. De Capua,D. Dutta,C. Fitzpatrick,E. Gersabeck,M. Gersabeck,L. Grillo,M. Hilton,G. Lafferty,J. J. Lane,A. Lupato,T. H. Mcgrath,A. McNab,B. Mitreska,D. Murray,Y. Pan,C. Parkes,F. Reiss,N. Skidmore,P. Svihra,S. Taneja,D. J. White&G. Zunica
Petersburg Nuclear Physics Institute NRC Kurchatov Institute (PNPI NRC KI), Gatchina, Russia
G. Alkhazov,A. Andreianov,N. Bondar,A. Chubykin,V. Chulikov,A. Dzyuba,D. Ilin,A. Inglessi,K. Ivshin,S. Kotriakhova,P. Kravchenko,O. Maev,D. Maisuzenko,N. Sagidova,A. Solovev,I. Solovyev,A. Vorobyev&N. Voropaev
Cavendish Laboratory, University of Cambridge, Cambridge, UK
P. Alvarez Cartelle,F. C. R. Bishop,H. V. Cliff,B. Delaney,V. Gibson,C. R. Jones,G. H. Lovell,J. G. Smeaton,I. Williams&S. A. Wotton
Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
S. Amato,L. De Paula,F. Ferreira Rodrigues,M. Gandelman,A. Hicheur,J. H. Lopes,L. Meyer Garcia,I. Nasteva,J. M. Otalora Goicochea,E. Polycarpo,M. S. Rangel,F. L. Souza De Almeida&B. Souza De Paula
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
Y. Amhis,S. Barsuk,J. A. B. Coelho,F. Desse,F. Machefert,E. M. Niel,P. Robbe,M. H. Schune&G. Wormser
INFN Sezione di Firenze, Firenze, Italy
L. Anderlini,A. Bizzeti,G. Graziani,S. Mariani,G. Passaleva&M. Veltri
INFN Sezione di Ferrara, Ferrara, Italy
M. Andreotti,W. Baldini,C. Bozzi,R. Calabrese,M. Fiorini,E. Franzoso,C. Giugliano,P. Griffith,M. Guarise,S. Kotriakhova,E. Luppi,A. Minotti,L. Minzoni,I. Neri,L. L. Pappalardo,B. Passalacqua,B. G. Siddi,I. Slazyk,L. Tomassetti&S. Vecchi
Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
F. Archilli,S. Bachmann,D. Berninghoff,M. Borsato,G. Frau,D. Gerick,J. P. Grabowski,P. A. Günther,X. Han,S. Hansmann-Menzemer,J. Hu,R. Kopecna,B. Leverington,P. Li,H. Malygina,J. Marks,D. J. Unverzagt,U. Uwer,C. Wang,L. Witola&A. Zhelezov
Institute for High Energy Physics NRC Kurchatov Institute (IHEP NRC KI), Protvino, Russia
A. Artamonov,K. Belous,Y. Guz,S. Kholodenko,V. Obraztsov,S. Poslavskii,V. Romanovskiy,M. Shapkin,O. Stenyakin&O. Yushchenko
Syracuse University, Syracuse, NY, USA
M. Artuso,B. Batsukh,A. Beiter,H. C. Bernstein,S. Blusk,S. Ely,Z. Li,X. Liang,R. Mountain,M. E. Olivares,T. T. H. Pham,M. Poliakova,I. Polyakov,M. S. Rudolph,J. D. Shupperd,T. Skwarnicki,S. Stone,A. Venkateswaran,M. Wilkinson,H. Wu,Y. Yao&X. Yuan
Yandex School of Data Analysis, Moscow, Russia
K. Arzymatov,V. Belavin,M. Borisyak,T. Gaintseva,A. Philippov,S. Popov,F. Ratnikov&A. Ustyuzhanin
Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France
E. Aslanides,J. Cerasoli,J. Cogan,D. Gerstel,R. Le Gac,O. Leroy,G. Mancinelli,C. Meaux,P. K. Resmi,A. Poluektov,R. I. Rabadan Trejo&D. Vom Bruch
Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
B. Audurier,V. Balagura,F. Fleuret,F. A. Garcia Rosales&E. Maurice
Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
M. Bachmayer,A. Bay,V. Bellee,F. Blanc,S. A. Bouchiba,S. Celani,S. Cholak,M. De Cian,S. Ek-In,L. Ferreira Lopes,E. Graverini,G. Haefeli,D. Hill,V. S. Kirsebom,V. Macko,M. Marinangeli,T. Nakada,T. Nanut,T. D. Nguyen,C. Nguyen-Mau,G. Pietrzyk,F. Redi,A. B. Rodrigues,O. Schneider,S. Schulte,L. Shchutska,P. Stefko,M. E. Stramaglia,M. T. Tran,C. Trippl,A. Tully,M. Van Dijk,M. Vieites Diaz&E. Zaffaroni
Department of Physics, University of Warwick, Coventry, UK
J. J. Back,T. Blake,A. Brossa Gonzalo,M. F. Cicala,C. M. Costa Sobral,L. M. Garcia Martin,T. Gershon,R. J. Hunter,T. P. Jones,M. Kenzie,M. Kreps,T. Latham,O. Lupton,E. Millard,A. G. Morris,B. Pagare,M. Ramos Pernas,N. Sahoo&M. Vesterinen
Centro Brasileiro de Pesquisas Físicas (CBPF), Rio de Janeiro, Brazil
J. Baptista Leite,I. Bediaga,M. Cruz Torres,J. M. De Miranda,A. C. dos Reis,A. Gomes,A. Massafferri,G. Punzi&D. Torres Machado
Imperial College London, London, UK
W. Barter,M. Birch,M. J. Bradley,A. Golutvin,M. Hecker,F. Kress,T. Lin,M. McCann,R. D. Moise,R. Newcombe,M. Patel,M. Smith&D. Websdale
INFN Sezione di Genova, Genova, Italy
M. Bartolini,R. Cardinale,F. Fontanelli,A. Petrolini&A. Sergi
National University of Science and Technology ‘MISIS’, Moscow, Russia
F. Baryshnikov,S. Didenko,A. Golutvin,S. Gromov,A. Ishteev,A. Kondybayeva,S. Legotin,N. Polukhina,D. Saranin,I. Shchemerov,E. Shmanin,O. Steinkamp,D. Strekalina,E. Trifonova,E. Ursov&E. van Herwijnen
I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany
J. M. Basels,L. Carus,S. Escher,A. Guth,J. Heuel,T. Kirn,S. Kretzschmar,C. Langenbruch,M. Materok,S. Nieswand,S. Schael,E. Smith&V. Zhukov
INFN Sezione di Pisa, Pisa, Italy
G. Bassi,F. Bedeschi,F. Lazzari,A. Lusiani,M. J. Morello,L. Pica,M. Rama,R. Ribatti,G. Tuci&J. Walsh
INFN Sezione di Cagliari, Monserrato, Italy
S. Belin,D. Brundu,S. Cadeddu,A. Cardini,A. Contu,F. Dettori,F. Dordei,M. Garau,A. Lai,A. Lampis,R. Litvinov,A. Loi,G. Manca,P. Muzzetto,R. Oldeman,B. Saitta&J. Sun
Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia
I. Belov,A. Berezhnoy,I. V. Gorelov,M. Korolev,A. Leflat,N. Nikitin,D. Savrina&V. Zhukov
Institute of Theoretical and Experimental Physics NRC Kurchatov Institute (ITEP NRC KI), Moscow, Russia
I. Belyaev,A. Danilina,V. Egorychev,D. Golubkov,P. Gorbounov,A. Konoplyannikov,T. Kvaratskheliya,V. Matiunin,T. Ovsiannikova,D. Pereima,D. Savrina,A. sem*nnikov&A. Smetkina
INFN Laboratori Nazionali di Frascati, Frascati, Italy
G. Bencivenni,L. Calero Diaz,S. Cali,P. Campana,P. Ciambrone,P. De Simone,P. Di Nezza,M. Giovannetti,G. Lanfranchi,G. Morello,M. Palutan,M. Poli Lener,M. Rotondo,M. Santimaria&B. Sciascia
LPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3, Paris, France
E. Ben-Haim,P. Billoir,L. Calefice,M. Charles,L. Del Buono,S. Esen,M. Fontana,V. V. Gligorov,T. Grammatico,F. Polci,R. Quagliani,D. Y. Tou,P. Vincent&S. G. Weber
Universita degli Studi di Padova, Universita e INFN, Padova, Padova, Italy
A. Bertolin,D. Lucchesi,M. Morandin,L. Sestini,G. Simi&D. Zuliani
Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland
J. Bhom,J. T. Borsuk,J. Brodzicka,A. Chernov,M. Chrzaszcz,M. W. Dudek,A. Dziurda,M. Goncerz,M. Jezabek,W. Kucewicz,M. Kucharczyk,T. Lesiak,J. J. Malczewski,A. Ossowska,K. Prasanth,M. Witek&M. Zdybal
School of Physics and Technology, Wuhan University, Wuhan, China
L. Bian,H. Cai,B. Fang,X. Huang,L. Sun&J. Wang
University of Birmingham, Birmingham, UK
S. Bifani,R. Calladine,G. Chatzikonstantinidis,N. Cooke,J. Plews,M. W. Slater,P. N. Swallow&N. K. Watson
Università di Modena e Reggio Emilia, Modena, Italy
A. Bizzeti
Department of Physics, University of Oxford, Oxford, UK
M. Bjørn,K. M. Fischer,F. Goncalves Abrantes,B. R. Gruberg Cazon,T. H. Hanco*ck,N. Harnew,M. John,L. Li,S. Malde,R. A. Mohammed,C. H. Murphy,T. Pajero,M. Pili,H. Pullen,V. Renaudin,A. Rollings,L. G. Scantlebury Smead,J. C. Smallwood,F. Suljik,G. Wilkinson&Y. Zhang
Massachusetts Institute of Technology, Cambridge, MA, USA
T. Boettcher,D. C. Craik,O. Kitouni,C. Weisser&M. Williams
National Research University Higher School of Economics, Moscow, Russia
A. Boldyrev,D. Derkach,M. Hushchyn,M. Karpov,A. Maevskiy,F. Ratnikov,A. Ryzhikov&A. Ustyuzhanin
Budker Institute of Nuclear Physics (SB RAS), Novosibirsk, Russia
A. Bondar,S. Eidelman,P. Krokovny,V. Kudryavtsev,T. Maltsev,L. Shekhtman&V. Vorobyev
University of Maryland, College Park, MD, USA
S. Braun,A. D. Fernez,M. Franco Sevilla,P. M. Hamilton,A. Jawahery,W. Parker,Y. Sun&Z. Yang
Guangdong Provencial Key Laboratory of Nuclear Science, Institute of Quantum Matter, South China Normal University, Guangzhou, China
A. Bursche,J. Hu,H. Li&G. Liu
Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS), Moscow, Russia
A. Butkevich,S. Filippov,E. Gushchin,L. Kravchuk&S. Luchuk
Università di Ferrara, Ferrara, Italy
R. Calabrese,M. Fiorini,P. Griffith,E. Luppi,L. Minzoni,L. L. Pappalardo,I. Slazyk&L. Tomassetti
INFN Sezione di Milano-Bicocca, Milano, Italy
M. Calvi,S. Capelli,P. Carniti,D. Fazzini,J. García Pardiñas,C. Gotti,M. Martinelli,C. Matteuzzi,S. Meloni&E. B. Shields
Università di Milano Bicocca, Milano, Italy
M. Calvi,S. Capelli,P. Carniti,D. Fazzini,J. García Pardiñas,L. Martinazzoli,M. Martinelli,S. Meloni&E. B. Shields
DS4DS, La Salle, Universitat Ramon Llull, Barcelona, Spain
M. Calvo Gomez,A. Camboni,E. Golobardes,N. Valls Canudas&X. Vilasis-Cardona
University of Chinese Academy of Sciences, Beijing, China
A. F. Campoverde Quezada,Y. Fan,J. He,W. Huang,H. Liu,X. Lyu,R. Ma,W. Qian,J. Qin,Z. Xiang,J. Xu,Q. Xu,Z. Xu,S. Yang,Y. Yang,Y. Zheng,X. Zhou,Y. Zhou&Z. Zhu
INFN Sezione di Bologna, Bologna, Italy
L. Capriotti,A. Carbone,A. Falabella,F. Ferrari,D. Galli,S. Maccolini,D. Manuzzi,U. Marconi,C. Patrignani,S. Perazzini,M. Soares,V. Vagnoni,G. Valenti&S. Zucchelli
Università di Bologna, Bologna, Italy
L. Capriotti,A. Carbone,F. Ferrari,D. Galli,S. Maccolini,D. Manuzzi,C. Patrignani&S. Zucchelli
INFN Sezione di Roma Tor Vergata, Roma, Italy
G. Carboni,E. Santovetti&A. Satta
Institute Of High Energy Physics (IHEP), Beijing, China
I. Carli,S. Chen,Y. Li,Y. Li,S. Liu,Y. Lu,L. Ma,M. Tobin,J. Wang&Q. Zou
Univ. Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France
M. Chefdeville,D. Decamp,A. G. Downes,Ph. Ghez,J. F. Marchand,M.-N. Minard,B. Pietrzyk,B. Quintana,M. Reboud&S. T’Jampens
Center for High Energy Physics, Tsinghua University, Beijing, China
C. Chen,J. Fan,Y. Gan,G. Gong,C. Gu,F. Jiang,Y. Kang,X. Liu,Y. Luo,H. Mu,Z. Ren,J. Wang,M. Wang,Z. Wang,L. Xu,D. Yang,Z. Yang,M. Zeng,L. Zhang&X. Zhu
School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
P. E. L. Clarke,R. Currie,S. Eisenhardt,S. Gambetta,K. Gizdov,S. E. Mitchell,F. Muheim,M. Needham,S. Petrucci,G. Robertson,M. R. J. Williams&J. B. Zonneveld
Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania
L. Cojocariu,A. Ene,L. Giubega,A. Grecu,F. Maciuc,V. Placinta&M. Straticiuc
INFN Sezione di Bari, Bari, Italy
L. Congedo,M. De Serio,R. A. Fini,A. Palano,M. Pappagallo,A. Pastore&S. Simone
Università di Bari, Bari, Italy
L. Congedo,M. De Serio,M. Pappagallo&S. Simone
Los Alamos National Laboratory (LANL), Los Alamos, NM, USA
J. Crkovská,C. L. Da Silva,C. T. Dean,J. M. Durham,E. Epple&G. J. Kunde
Van Swinderen Institute, University of Groningen, Groningen, Netherlands
K. De Bruyn,C. J. G. Onderwater&M. van Veghel
Universiteit Maastricht, Maastricht, Netherlands
J. A. de Vries,M. Merk&C. J. Pawley
Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Kraków, Poland
A. Dendek,M. Firlej,T. Fiutowski,M. Idzik,P. Kopciewicz,W. Krupa,O. Madejczyk,M. W. Majewski,J. Moron,A. Oblakowska-Mucha,B. Rachwal,J. Ryzka,K. Swientek&T. Szumlak
Università di Cagliari, Cagliari, Italy
F. Dettori,C. Giugliano,G. Manca,R. Oldeman&B. Saitta
Eotvos Lorand University, Budapest, Hungary
B. Dey
Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine
V. Dobishuk,S. Koliiev,I. Kostiuk,O. Kot&V. Pugatch
School of Physics, University College Dublin, Dublin, Ireland
A. M. Donohoe,L. Mcconnell,R. McNulty,N. V. Raab&C. B. Van Hulse
NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine
A. Dovbnya&S. Kandybei
INFN Sezione di Perugia, Perugia, Italy
V. Duk&M. Piccini
STFC Rutherford Appleton Laboratory, Didcot, UK
S. Easo,R. Nandakumar,A. Papanestis,S. Ricciardi&F. F. Wilson
School of Physics and Astronomy, Monash University, Melbourne, Victoria, Australia
U. Egede&T. Hadavizadeh
Novosibirsk State University, Novosibirsk, Russia
S. Eidelman,P. Krokovny,V. Kudryavtsev,T. Maltsev,L. Shekhtman&V. Vorobyev
Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
L. Eklund
Università di Genova, Genova, Italy
F. Fontanelli&A. Petrolini
School of Physics State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China
Y. Gao,Y. Shang,Z. Shen,J. Wang,A. Xu,Z. Xu,S. Zhang&Y. Zhang
National Center for Nuclear Research (NCBJ), Warsaw, Poland
H. K. Giemza,K. Klimaszewski,W. Krzemien,D. Melnychuk,A. Szabelski,A. Ukleja&W. Wislicki
Università di Roma Tor Vergata, Roma, Italy
M. Giovannetti&E. Santovetti
Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil
C. Göbel
Universidade Federal do Triângulo Mineiro (UFTM), Uberaba-MG, Brazil
A. Gomes
Institute of Particle Physics, Central China Normal University, Wuhan, China
Q. Han,W. Hu,S. Li,Y. Wang,D. Xiao,Y. Xie,M. Xu,H. Yin&D. Zhang
Hangzhou Institute for Advanced Study, UCAS, Hangzhou, China
J. He
Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia - CSIC, Valencia, Spain
L. Henry,B. K. Jashal,F. Martinez Vidal,A. Oyanguren,C. Remon Alepuz&J. Ruiz Vidal
Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, Netherlands
T. Ketel,H. S. Kuindersma,G. Raven&M. Senghi Soares
National Research Tomsk Polytechnic University, Tomsk, Russia
A. Kharisova,G. Panshin&A. Vagner
Faculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, Kraków, Poland
W. Kucewicz
Università di Siena, Siena, Italy
F. Lazzari
Università di Padova, Padova, Italy
D. Lucchesi
Scuola Normale Superiore, Pisa, Italy
A. Lusiani&M. J. Morello
National Research Centre Kurchatov Institute, Moscow, Russia
A. Malinin,A. Petrov&V. Shevchenko
Università degli Studi di Milano, Milano, Italy
D. Marangotto,N. Neri&E. Spadaro Norella
MSU–Iligan Institute of Technology (MSU-IIT), Iligan, Philippines
J. Maratas
Università di Firenze, Firenze, Italy
S. Mariani
INFN Sezione di Roma La Sapienza, Roma, Italy
G. Martellotti,D. Pinci,R. Santacesaria,A. Sarti&C. Satriano
Institut für Physik, Universität Rostock, Rostock, Germany
N. Meinert,H. Viemann&R. Waldi
Departamento de Fisica, Universidad Nacional de Colombia, Bogota, Colombia
D. A. Milanes,I. A. Monroy&J. A. Rodriguez Lopez
Universität Bonn Helmholtz-Institut für Strahlen und Kernphysik, Bonn, Germany
A. B. Morris,S. Neubert&M. Sarpis
Hanoi University of Science, Hanoi, Vietnam
C. Nguyen-Mau
Università di Pisa, Pisa, Italy
L. Pica,G. Punzi&G. Tuci
P.N. Lebedev Physical Institute, Russian Academy of Sciences (LPI RAS), Moscow, Russia
N. Polukhina&M. Zavertyaev
Università della Basilicata, Potenza, Italy
C. Satriano
Max-Planck-Institut für Kernphysik (MPIK), Heidelberg, Germany
M. Schmelling&M. Zavertyaev
Università di Urbino, Urbino, Italy
M. Veltri
Physics and Micro Electronic College, Hunan University, Changsha City, China
J. Yu

Consortia

LHCb collaboration

R. Aaij
,C. Abellán Beteta
,T. Ackernley
,B. Adeva
,M. Adinolfi
,H. Afsharnia
,C. A. Aidala
,S. Aiola
,Z. Ajaltouni
,S. Akar
,J. Albrecht
,F. Alessio
,M. Alexander
,A. Alfonso Albero
,Z. Aliouche
,G. Alkhazov
,P. Alvarez Cartelle
,S. Amato
,Y. Amhis
,L. An
,L. Anderlini
,A. Andreianov
,M. Andreotti
,F. Archilli
,A. Artamonov
,M. Artuso
,K. Arzymatov
,E. Aslanides
,M. Atzeni
,B. Audurier
,S. Bachmann
,M. Bachmayer
,J. J. Back
,P. Baladron Rodriguez
,V. Balagura
,W. Baldini
,J. Baptista Leite
,R. J. Barlow
,S. Barsuk
,W. Barter
,M. Bartolini
,F. Baryshnikov
,J. M. Basels
,G. Bassi
,B. Batsukh
,A. Battig
,A. Bay
,M. Becker
,F. Bedeschi
,I. Bediaga
,A. Beiter
,V. Belavin
,S. Belin
,V. Bellee
,K. Belous
,I. Belov
,I. Belyaev
,G. Bencivenni
,E. Ben-Haim
,A. Berezhnoy
,R. Bernet
,D. Berninghoff
,H. C. Bernstein
,C. Bertella
,A. Bertolin
,C. Betancourt
,F. Betti
,Ia. Bezshyiko
,S. Bhasin
,J. Bhom
,L. Bian
,M. S. Bieker
,S. Bifani
,P. Billoir
,M. Birch
,F. C. R. Bishop
,A. Bitadze
,A. Bizzeti
,M. Bjørn
,M. P. Blago
,T. Blake
,F. Blanc
,S. Blusk
,D. Bobulska
,J. A. Boelhauve
,O. Boente Garcia
,T. Boettcher
,A. Boldyrev
,A. Bondar
,N. Bondar
,S. Borghi
,M. Borisyak
,M. Borsato
,J. T. Borsuk
,S. A. Bouchiba
,T. J. V. Bowco*ck
,A. Boyer
,C. Bozzi
,M. J. Bradley
,S. Braun
,A. Brea Rodriguez
,M. Brodski
,J. Brodzicka
,A. Brossa Gonzalo
,D. Brundu
,A. Buonaura
,C. Burr
,A. Bursche
,A. Butkevich
,J. S. Butter
,J. Buytaert
,W. Byczynski
,S. Cadeddu
,H. Cai
,R. Calabrese
,L. Calefice
,L. Calero Diaz
,S. Cali
,R. Calladine
,M. Calvi
,M. Calvo Gomez
,P. Camargo Magalhaes
,A. Camboni
,P. Campana
,A. F. Campoverde Quezada
,S. Capelli
,L. Capriotti
,A. Carbone
,G. Carboni
,R. Cardinale
,A. Cardini
,I. Carli
,P. Carniti
,L. Carus
,K. Carvalho Akiba
,A. Casais Vidal
,G. Casse
,M. Cattaneo
,G. Cavallero
,S. Celani
,J. Cerasoli
,A. J. Chadwick
,M. G. Chapman
,M. Charles
,Ph. Charpentier
,G. Chatzikonstantinidis
,C. A. Chavez Barajas
,M. Chefdeville
,C. Chen
,S. Chen
,A. Chernov
,V. Chobanova
,S. Cholak
,M. Chrzaszcz
,A. Chubykin
,V. Chulikov
,P. Ciambrone
,M. F. Cicala
,X. Cid Vidal
,G. Ciezarek
,P. E. L. Clarke
,M. Clemencic
,H. V. Cliff
,J. Closier
,J. L. Cobbledick
,V. Coco
,J. A. B. Coelho
,J. Cogan
,E. Cogneras
,L. Cojocariu
,P. Collins
,T. Colombo
,L. Congedo
,A. Contu
,N. Cooke
,G. Coombs
,G. Corti
,C. M. Costa Sobral
,B. Couturier
,D. C. Craik
,J. Crkovská
,M. Cruz Torres
,R. Currie
,C. L. Da Silva
,E. Dall’Occo
,J. Dalseno
,C. D’Ambrosio
,A. Danilina
,P. d’Argent
,A. Davis
,O. De Aguiar Francisco
,K. De Bruyn
,S. De Capua
,M. De Cian
,J. M. De Miranda
,L. De Paula
,M. De Serio
,D. De Simone
,P. De Simone
,J. A. de Vries
,C. T. Dean
,D. Decamp
,L. Del Buono
,B. Delaney
,H.-P. Dembinski
,A. Dendek
,V. Denysenko
,D. Derkach
,O. Deschamps
,F. Desse
,F. Dettori
,B. Dey
,P. Di Nezza
,S. Didenko
,L. Dieste Maronas
,H. Dijkstra
,V. Dobishuk
,A. M. Donohoe
,F. Dordei
,A. C. dos Reis
,L. Douglas
,A. Dovbnya
,A. G. Downes
,K. Dreimanis
,M. W. Dudek
,L. Dufour
,V. Duk
,P. Durante
,J. M. Durham
,D. Dutta
,A. Dziurda
,A. Dzyuba
,S. Easo
,U. Egede
,V. Egorychev
,S. Eidelman
,S. Eisenhardt
,S. Ek-In
,L. Eklund
,S. Ely
,A. Ene
,E. Epple
,S. Escher
,J. Eschle
,S. Esen
,T. Evans
,A. Falabella
,J. Fan
,Y. Fan
,B. Fang
,S. Farry
,D. Fazzini
,M. Féo
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Contributions

All contributing authors, as listed at the end of the manuscript, have contributed to the publication, being variously involved in the design and construction of the detector, writing software, calibrating sub-systems, operating the detector, acquiring data and analysing the processed data.

Corresponding author

Correspondence to A. Bertolin.

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Extended data

Extended Data Fig. 1 Simulated K+e− mass distributions for signal and various cascade background samples.

The signal is represented by the orange shaded region and the various cascade background contributions by red, dark blue and light blue shaded regions. The distributions are all normalised to unity. (Left, with log y-scale) the bremsstrahlung correction to the momentum of the electron is applied, resulting in a tail to the right. The region to the left of the vertical dashed line is rejected. (Right, with linear y-scale) the mass is computed only from the track information. The notation \({\pi }_{[\to {e}^{-}]}^{-}\) (\({e}_{[\to {\pi }^{-}]}^{-}\)) is used to denote an pion (electron) that is reconstructed as an electron (pion). The region between the dashed vertical lines is rejected.

Extended Data Fig. 2 Nonresonant candidates invariant mass distributions.

Distribution of the invariant mass m(K⁺ℓ⁺ℓ⁻) for nonresonant candidates in the (left) sample previously analysed¹¹ and (right) the new data sample. The top row shows the fit to the muon modes and the subsequent rows the fits to the electron modes triggered by (second row) one of the electrons, (third row) the kaon and (last row) by other particles in the event. The fit projections are superimposed, with dotted lines describing the signal contribution and solid areas representing each of the background components described in the text and listed in the legend. Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. The y-axis in each figure shows the number of candidates in an interval of the indicated width.

Extended Data Fig. 3 Resonant candidates invariant mass distributions.

Distribution of the invariant mass m_J/ψ(K⁺ℓ⁺ℓ⁻) for resonant candidates in the (left) sample previously analysed¹¹ and (right) the new data sample. The top row shows the fit to the muon modes and the subsequent rows the fits to the electron modes triggered by (second row) one of the electrons, (third row) the kaon and (last row) by other particles in the event. The fit projections are superimposed, with dotted lines describing the signal contribution and solid areas representing each of the background components described in the text and listed in the legend. Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. The y-axis in each figure shows the number of candidates in an interval of the indicated width.

Extended Data Fig. 4 Likelihood function from the fit to the nonresonant B+ → K+ℓ+ℓ− candidates.

Ratio between the likelihood value (L) and that found by the fit (\({L}_{\max }\)) as a function of R_K. The extent of the dark, medium and light blue regions shows the values allowed for R_K at 1σ, 3σ and 5σ levels. The red line indicates the prediction from the SM.

Extended Data Fig. 5 Differential rJ/ψ measurement.

(Top) distributions of the reconstructed spectra of (left) the angle between the leptons, α(ℓ⁺, ℓ⁻), and (right) the minimum p_T of the leptons for B⁺ → K⁺ℓ⁺ℓ⁻ and B⁺ → J/ψ( → ℓ⁺ℓ⁻)K⁺ decays. (Bottom) the single ratio r_J/ψ relative to its average value \(< {r}_{J/\psi } >\) as a function of these variables. In the electron minimum p_T spectra, the structure at 2800 MeV/c is related to the trigger threshold. Uncertainties on the data points are statistical only and represent one standard deviation.

Extended Data Fig. 6 Double differential rJ/ψ measurement.

(Left) the value of r_J/ψ, relative to the average value of r_J/ψ, measured in two-dimensional bins of the maximum lepton momentum, p(ℓ), and the opening angle between the two leptons, α(ℓ⁺, ℓ⁻). (Right) the bin definition in this two-dimensional space together with the distribution for B⁺ → K⁺e⁺e⁻ (B⁺ → J/ψ( → e⁺e⁻)K⁺) decays depicted as red (blue) contours. Uncertainties on the data points are statistical only and represent one standard deviation.

Extended Data Fig. 7 Distribution of m(K+e+e−) in simulated B+ → K+e+e− decays.

Distribution of m(K⁺e⁺e⁻) in simulated B⁺ → K⁺e⁺e⁻ decays. The orange shaded area corresponds to B⁺ → K⁺e⁺e⁻ candidates with true q² (\({q}_{{{{\rm{t}}}}rue}^{2}\)) outside the [1.1, 6.0] GeV ²/c⁴ interval. The green and purple components correspond to candidates with \({q}_{{{{\rm{t}}}}rue}^{2} > 6.0\) GeV ²/c⁴ and \({q}_{{{{\rm{t}}}}rue}^{2} < 1.1\) GeV ²/c⁴, respectively. Linear (top) and logarithmic (bottom) scales are shown.

Extended Data Fig. 8 Candidate invariant mass distributions.

Distribution of the invariant mass m(K⁺e⁺e⁻) for B⁺ → K⁺e⁺e⁻ candidates. The fit projection is superimposed, with a black dotted line describing the signal contribution and solid areas representing each of the background components described in the text and listed in the legend. For illustration, the expected distribution of signal candidates with true q² outside the interval [1.1, 6.0]GeV²/c⁴ is shown as a grey dashed and dotted line. Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. The y-axis in each figure shows the number of candidates in an interval of the indicated width.

Extended Data Table 1 Nonresonant and resonant mode q2 and m(K+ℓ+ℓ−) ranges.

The variables m(K⁺ℓ⁺ℓ⁻) and m_J/ψ(K⁺ℓ⁺ℓ⁻) are used for nonresonant and resonant decays, respectively.

Extended Data Table 2 Yields of the nonresonant and resonant decay modes.

Yields of the nonresonant and resonant decay modes obtained from the fits to the data. The quoted uncertainty is the combination of statistical and systematic effects.

Supplementary information

Supplementary references.

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LHCb collaboration. Test of lepton universality in beauty-quark decays. Nat. Phys. 18, 277–282 (2022). https://doi.org/10.1038/s41567-021-01478-8

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Received: 22 March 2021
Accepted: 30 November 2021
Published: 15 March 2022
Issue Date: March 2022
DOI: https://doi.org/10.1038/s41567-021-01478-8