Evidence for the Rare Decay B+ → Λ ¯ pμ+μ

(LHCb Collaboration)

doi:10.1103/pl88-4435

Evidence for the Rare Decay B+ → Λ ¯ pμ+μ

(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
University of Glasgow
Uppsala University
Université Paris-Saclay
University of Michigan, Ann Arbor
Université Clermont Auvergne
AGH University of Krakow
National Institute for Nuclear Physics
TU Dortmund University
Lamarr Institute for Machine Learning and Artificial Intelligence
University of Freiburg
Vilnius University
CERN
University of Cambridge
Sorbonne Université
Universidade Federal do Rio de Janeiro
Peking University
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University of Milan - Bicocca
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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
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CAS - Institute of High Energy Physics
Eötvös Loránd University
Ramon Llull University
Kyiv National Taras Shevchenko University
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
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Monash University
Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences
Cracow University of Technology
Ohio State University
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University of Barcelona
Universidade Estadual de Campinas
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Scuola Normale Superiore di Pisa
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Horia Hulubei National Institute of Physics and Nuclear Engineering
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Centro Federal de Educação Tecnológica Celso Suckow da Fonseca
University of Bari
Central China Normal University
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Rutherford Appleton Laboratory
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NASU - Kharkov Institute of Physics and Technology
National Centre for Nuclear Research
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Universidad Nacional de Colombia
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University of Birmingham
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Max Planck Institute for Nuclear Physics
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Research output: Contribution to journal › Article › peer-review

Abstract

A search for the rare decay B+→Λ¯pμ+μ- is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of s=13 TeV, corresponding to an integrated luminosity of 5.4 fb-1. An excess of events is found with respect to the background-only expectation, with a signal significance of 3.5 standard deviations, in the low invariant-mass region of m(Λ¯p)<2.8 GeV/c2. The branching fraction is measured to be Blow(B+→Λ¯pμ+μ-)=(1.70-0.56+0.65(stat)±0.17(syst)±0.14(ext))×10-8, where the last uncertainty is due to external inputs on B(B+→J/ψΛ¯p)×B(J/ψ→μ+μ-). With no significant signal observed in the high m(Λ¯p) region above 2.8 GeV/c2, an upper limit is set to be Bhigh(B+→Λ¯pμ+μ-)<2.8(3.7)×10-9 at the 90% (95%) confidence level.

Original language	English
Article number	051801
Journal	Physical Review Letters
Volume	137
Issue number	5
DOIs	https://doi.org/10.1103/pl88-4435
State	Published - 31 Jul 2026
Externally published	Yes

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10.1103/pl88-4435

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@article{a3e53eea31be4fb497819f90cbe8bfa6,

title = "Evidence for the Rare Decay B+ → Λ ¯ pμ+μ",

abstract = "A search for the rare decay B+→Λ¯pμ+μ- is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of s=13 TeV, corresponding to an integrated luminosity of 5.4 fb-1. An excess of events is found with respect to the background-only expectation, with a signal significance of 3.5 standard deviations, in the low invariant-mass region of m(Λ¯p)<2.8 GeV/c2. The branching fraction is measured to be Blow(B+→Λ¯pμ+μ-)=(1.70-0.56+0.65(stat)±0.17(syst)±0.14(ext)){\texttimes}10-8, where the last uncertainty is due to external inputs on B(B+→J/ψΛ¯p){\texttimes}B(J/ψ→μ+μ-). With no significant signal observed in the high m(Λ¯p) region above 2.8 GeV/c2, an upper limit is set to be Bhigh(B+→Λ¯pμ+μ-)<2.8(3.7){\texttimes}10-9 at the 90\% (95\%) confidence level.",

author = "\{(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 M. Akthar 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 \{Calderon Ramirez\}, S.",

note = "Publisher Copyright: {\textcopyright} 2026 CERN. ",

year = "2026",

month = jul,

day = "31",

doi = "10.1103/pl88-4435",

language = "Ingl{\'e}s",

volume = "137",

journal = "Physical Review Letters",

issn = "0031-9007",

number = "5",

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TY - JOUR

T1 - Evidence for the Rare Decay B+ → Λ ¯ pμ+μ

AU - (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 - Akthar, M.

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 - Calderon Ramirez, S.

PY - 2026/7/31

Y1 - 2026/7/31

N2 - A search for the rare decay B+→Λ¯pμ+μ- is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of s=13 TeV, corresponding to an integrated luminosity of 5.4 fb-1. An excess of events is found with respect to the background-only expectation, with a signal significance of 3.5 standard deviations, in the low invariant-mass region of m(Λ¯p)<2.8 GeV/c2. The branching fraction is measured to be Blow(B+→Λ¯pμ+μ-)=(1.70-0.56+0.65(stat)±0.17(syst)±0.14(ext))×10-8, where the last uncertainty is due to external inputs on B(B+→J/ψΛ¯p)×B(J/ψ→μ+μ-). With no significant signal observed in the high m(Λ¯p) region above 2.8 GeV/c2, an upper limit is set to be Bhigh(B+→Λ¯pμ+μ-)<2.8(3.7)×10-9 at the 90% (95%) confidence level.

AB - A search for the rare decay B+→Λ¯pμ+μ- is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of s=13 TeV, corresponding to an integrated luminosity of 5.4 fb-1. An excess of events is found with respect to the background-only expectation, with a signal significance of 3.5 standard deviations, in the low invariant-mass region of m(Λ¯p)<2.8 GeV/c2. The branching fraction is measured to be Blow(B+→Λ¯pμ+μ-)=(1.70-0.56+0.65(stat)±0.17(syst)±0.14(ext))×10-8, where the last uncertainty is due to external inputs on B(B+→J/ψΛ¯p)×B(J/ψ→μ+μ-). With no significant signal observed in the high m(Λ¯p) region above 2.8 GeV/c2, an upper limit is set to be Bhigh(B+→Λ¯pμ+μ-)<2.8(3.7)×10-9 at the 90% (95%) confidence level.

UR - https://www.scopus.com/pages/publications/105047163186

U2 - 10.1103/pl88-4435

DO - 10.1103/pl88-4435

M3 - Artículo

C2 - 42606492

AN - SCOPUS:105047163186

SN - 0031-9007

VL - 137

JO - Physical Review Letters

JF - Physical Review Letters

IS - 5

M1 - 051801

ER -

Evidence for the Rare Decay B+ → Λ ¯ pμ+μ

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