Branching fraction measurement of the Λ→pμ−ν¯μ decay

The LHCb collaboration

doi:10.1007/JHEP04(2026)096

Branching fraction measurement of the Λ→pμ−ν¯μ decay

The LHCb collaboration

National Institute for Subatomic Physics
University of Warwick
University of Zurich
University of Liverpool
Syracuse University
Instituto Galego de Física de Altas Enerxías (IGFAE)
University of Bristol
Uppsala University
Université Paris-Saclay
University of Michigan, Ann Arbor
Université Clermont Auvergne
National Institute for Nuclear Physics
TU Dortmund University
Lamarr Institute for Machine Learning and Artificial Intelligence
Vilnius University
CERN
University of Cambridge
Sorbonne Université
Universidade Federal do Rio de Janeiro
Peking University
University of A Coruna
University of Milan - Bicocca
University of Chinese Academy of Sciences
University of Rome Tor Vergata
Consejo Nacional de Rectores (CONARE)
CPPM
Swiss Federal Institute of Technology Lausanne
Massachusetts Institute of Technology
Laboratoire Leprince-Ringuet
University of Oxford
Heidelberg University
Ruhr University Bochum
Centro Brasileiro de Pesquisas Físicas
Pontifícia Universidade Católica do Rio de Janeiro
University of Manchester
University of Edinburgh
AGH University of Krakow
CAS - Institute of High Energy Physics
Ramon Llull University
Kyiv National Taras Shevchenko University
Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences
University of Bonn
Imperial College London
Université Savoie Mont Blanc
University of Modena and Reggio Emilia
University of Victoria BC
Los Alamos National Laboratory
Maastricht University
University of Ferrara
Monash University
Cracow University of Technology
Ohio State University
Wuhan University
University of Barcelona
Universidade Estadual de Campinas
University of Bologna
University of Genoa
Scuola Normale Superiore di Pisa
University of Milan
Tsinghua University
Eötvös Loránd University
NASU - Institute of Nuclear Research
Horia Hulubei National Institute of Physics and Nuclear Engineering
University of Glasgow
University of Cincinnati
National Autonomous University of Honduras
Hunan University
University of Cagliari
University of Groningen
Centro Federal de Educação Tecnológica Celso Suckow da Fonseca
University of Bari
Central China Normal University
University College Dublin
South China Normal University
Rutherford Appleton Laboratory
University of Perugia
University of Valencia
University of Maryland, College Park
NASU - Kharkov Institute of Physics and Technology
University of Freiburg
University of Padua
National Centre for Nuclear Research
University of Pisa
RWTH Aachen University
Universidad Nacional de Colombia
University of Birmingham
Vrije Universiteit Amsterdam
Henan Normal University
Lanzhou University
University of Bergamo
Universidad de Ingeniería y Tecnología
University of Siena
University of Basilicata
Max Planck Institute for Nuclear Physics
University of Alcalá
University of Urbino
Universidad Andrés Bello

Research output: Contribution to journal › Article › peer-review

Abstract

A measurement of the branching fraction for the decay Λ→pμ−ν¯μ is presented using pp collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb⁻¹. The result is obtained using Λ → pμ⁻ decays as a normalisation channel. The measured branching fraction is BΛ→pμ−ν¯μ=1.462±0.016±0.100±0.011×10−4, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalisation mode branching fraction, respectively. This result improves the precision of the branching fraction measurement by a factor of two compared to the previous best measurement and sets a more stringent bound on lepton flavour universality in s → u quark transitions. It is consistent with previous measurements, and the extracted lepton flavour universality test observable, Rμe=ΓΛ→pμ−ν¯μΓΛ→pe−ν¯e=0.175±0.012, agrees with the Standard Model prediction.

Original language	English
Article number	96
Journal	Journal of High Energy Physics
Volume	2026
Issue number	4
DOIs	https://doi.org/10.1007/JHEP04(2026)096
State	Published - Apr 2026
Externally published	Yes

Keywords

Branching fraction
Electroweak Interaction
Flavour Physics
Hadron-Hadron Scattering

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10.1007/JHEP04(2026)096

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title = "Branching fraction measurement of the Λ→pμ−ν¯μ decay",

abstract = "A measurement of the branching fraction for the decay Λ→pμ−ν¯μ is presented using pp collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb−1. The result is obtained using Λ → pμ− decays as a normalisation channel. The measured branching fraction is BΛ→pμ−ν¯μ=1.462±0.016±0.100±0.011×10−4, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalisation mode branching fraction, respectively. This result improves the precision of the branching fraction measurement by a factor of two compared to the previous best measurement and sets a more stringent bound on lepton flavour universality in s → u quark transitions. It is consistent with previous measurements, and the extracted lepton flavour universality test observable, Rμe=ΓΛ→pμ−ν¯μΓΛ→pe−ν¯e=0.175±0.012, agrees with the Standard Model prediction.",

keywords = "Branching fraction, Electroweak Interaction, Flavour Physics, Hadron-Hadron Scattering",

author = "\{The LHCb collaboration\} and R. Aaij and Abdelmotteleb, \{A. S.W.\} and \{Abellan Beteta\}, C. and F. Abudin{\'e}n and T. Ackernley and Adefisoye, \{A. A.\} and B. Adeva and M. Adinolfi and P. Adlarson and C. Agapopoulou and Aidala, \{C. A.\} and Z. Ajaltouni and S. Akar and K. Akiba and P. Albicocco and J. Albrecht and R. Aleksiejunas and F. Alessio and \{Alvarez Cartelle\}, P. and R. Amalric and S. Amato and Amey, \{J. L.\} and Y. Amhis and L. An and L. Anderlini and M. Andersson and P. Andreola and M. Andreotti and \{Andres Estrada\}, S. and A. Anelli and D. Ao and C. Arata and F. Archilli and Z. Areg and M. Argenton and \{Arguedas Cuendis\}, S. and L. Arnone and A. Artamonov and M. Artuso and E. Aslanides and \{Ata{\'i}de Da Silva\}, R. and M. Atzeni and B. Audurier and Authier, \{J. A.\} and D. Bacher and \{Bachiller Perea\}, I. and S. Bachmann and M. Bachmayer and Back, \{J. J.\} and \{Calderon Ramirez\}, S.",

note = "Publisher Copyright: {\textcopyright} The Author(s) 2026.",

year = "2026",

month = apr,

doi = "10.1007/JHEP04(2026)096",

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volume = "2026",

journal = "Journal of High Energy Physics",

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T1 - Branching fraction measurement of the Λ→pμ−ν¯μ decay

AU - The LHCb collaboration

AU - Aaij, R.

AU - Abdelmotteleb, A. S.W.

AU - Abellan Beteta, C.

AU - Abudinén, F.

AU - Ackernley, T.

AU - Adefisoye, A. A.

AU - Adeva, B.

AU - Adinolfi, M.

AU - Adlarson, P.

AU - Agapopoulou, C.

AU - Aidala, C. A.

AU - Ajaltouni, Z.

AU - Akar, S.

AU - Akiba, K.

AU - Albicocco, P.

AU - Albrecht, J.

AU - Aleksiejunas, R.

AU - Alessio, F.

AU - Alvarez Cartelle, P.

AU - Amalric, R.

AU - Amato, S.

AU - Amey, J. L.

AU - Amhis, Y.

AU - An, L.

AU - Anderlini, L.

AU - Andersson, M.

AU - Andreola, P.

AU - Andreotti, M.

AU - Andres Estrada, S.

AU - Anelli, A.

AU - Ao, D.

AU - Arata, C.

AU - Archilli, F.

AU - Areg, Z.

AU - Argenton, M.

AU - Arguedas Cuendis, S.

AU - Arnone, L.

AU - Artamonov, A.

AU - Artuso, M.

AU - Aslanides, E.

AU - Ataíde Da Silva, R.

AU - Atzeni, M.

AU - Audurier, B.

AU - Authier, J. A.

AU - Bacher, D.

AU - Bachiller Perea, I.

AU - Bachmann, S.

AU - Bachmayer, M.

AU - Back, J. J.

AU - Calderon Ramirez, S.

PY - 2026/4

Y1 - 2026/4

N2 - A measurement of the branching fraction for the decay Λ→pμ−ν¯μ is presented using pp collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb−1. The result is obtained using Λ → pμ− decays as a normalisation channel. The measured branching fraction is BΛ→pμ−ν¯μ=1.462±0.016±0.100±0.011×10−4, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalisation mode branching fraction, respectively. This result improves the precision of the branching fraction measurement by a factor of two compared to the previous best measurement and sets a more stringent bound on lepton flavour universality in s → u quark transitions. It is consistent with previous measurements, and the extracted lepton flavour universality test observable, Rμe=ΓΛ→pμ−ν¯μΓΛ→pe−ν¯e=0.175±0.012, agrees with the Standard Model prediction.

AB - A measurement of the branching fraction for the decay Λ→pμ−ν¯μ is presented using pp collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb−1. The result is obtained using Λ → pμ− decays as a normalisation channel. The measured branching fraction is BΛ→pμ−ν¯μ=1.462±0.016±0.100±0.011×10−4, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalisation mode branching fraction, respectively. This result improves the precision of the branching fraction measurement by a factor of two compared to the previous best measurement and sets a more stringent bound on lepton flavour universality in s → u quark transitions. It is consistent with previous measurements, and the extracted lepton flavour universality test observable, Rμe=ΓΛ→pμ−ν¯μΓΛ→pe−ν¯e=0.175±0.012, agrees with the Standard Model prediction.

KW - Branching fraction

KW - Electroweak Interaction

KW - Flavour Physics

KW - Hadron-Hadron Scattering

UR - https://www.scopus.com/pages/publications/105036710430

U2 - 10.1007/JHEP04(2026)096

DO - 10.1007/JHEP04(2026)096

M3 - Artículo

AN - SCOPUS:105036710430

SN - 1029-8479

VL - 2026

JO - Journal of High Energy Physics

JF - Journal of High Energy Physics

IS - 4

M1 - 96

ER -

Branching fraction measurement of the Λ→pμ−ν¯μ decay

Abstract

Keywords

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