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Observation of the Very Rare Σ+→𝑝⁢𝜇+⁢𝜇−Decay

  • LHCb Collaboration

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The first observation of the Σ+ →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±16  Σ+→𝑝⁢𝜇+⁢𝜇− decays is obtained, where the uncertainty is statistical only. A branching fraction of (1.08±0.17)×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.
Original languageEnglish
Article number051801
Pages (from-to)1-14
Number of pages14
JournalPhysical review letters
Volume135
Issue number5
Early online date29 Jul 2025
DOIs
Publication statusPublished - 1 Aug 2025

Funding

We express our gratitude to our colleagues in the CERN accelerator departments for the excellent performance of the LHC. We thank the technical and administrative staff at the LHCb institutes. We acknowledge support from CERN and from the national agencies: ARC (Australia); 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); MCID/IFA (Romania); MICIU and AEI (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); DOE NP and NSF (USA). We acknowledge the computing resources that are provided by ARDC (Australia), Centro Brasileiro de Pesquisas Físicas (CBPF) (Brazil), CERN, IHEP and LZU (China), IN2P3 (France), KIT and DESY (Germany), INFN (Italy), SURF (Netherlands), Polish WLCG (Poland), IFIN-HH (Romania), PIC (Spain), CSCS (Switzerland), and GridPP (United Kingdom). 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 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); Minciencias (Colombia); EPLANET, Marie Skłodowska-Curie Actions, ERC, and NextGenerationEU (European Union); A*MIDEX, ANR, IPhU and Labex P2IO, and Région Auvergne-Rhône-Alpes (France); Alexander-von-Humboldt Foundation (Germany); ICSC (Italy); Severo Ochoa and María de Maeztu Units of Excellence, GVA, XuntaGal, GENCAT, InTalent-Inditex and Prog. Atracción Talento CM (Spain); SRC (Sweden); the Leverhulme Trust, the Royal Society and UKRI (United Kingdom).

Funders
Ministerio de Ciencia, Innovación y Universidades
Agence Nationale de la Recherche
Australian Research Council
National Academy of Sciences of Ukraine
Narodowe Centrum Nauki
Institut national de physique nucléaire et de physique des particules
Science and Technology Facilities Council
H2020 Marie Skłodowska-Curie Actions
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Program of Guangzhou
Financiadora de Estudos e Projetos
Centre National de la Recherche Scientifique
Bundesministerium für Forschung, Technologie und Raumfahrt
NSF
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Deutsche Forschungsgemeinschaft
Canadian Anesthesiologists' Society
Région Auvergne-Rhône-Alpes
International Council of Shopping Centers
Agencia Estatal de Investigación
CAS Center for Excellence in Particle Physics
Ministry of Science and Technology of the People's Republic of China
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
NextGenerationEU
Sociedad Española de Reumatología
European Research Council
EPLANET
Ministerstwo Edukacji i Nauki
CERN
Nuclear Physics
Fundamental Research Funds for the Central Universities
Alexander von Humboldt-Stiftung
Istituto Nazionale di Fisica Nucleare
National Natural Science Foundation of China

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