Observation of the Rare Baryonic Decay B+ →p Λ  ̄ and Measurement of its Weak Decay Parameter

LHCb Collaboration

doi:10.1103/fj4q-t8jg

Observation of the Rare Baryonic Decay B+ →p Λ ̄ and Measurement of its Weak Decay Parameter

LHCb Collaboration

National Institute for Subatomic Physics
University of Warwick
University of Zurich
University of Liverpool
Syracuse University
University of Santiago de Compostela
University of Bristol
School of Physics and Astronomy
University of Glasgow
Department of Physics and Astronomy
Uppsala University
Université Paris-Saclay
University of Michigan, Ann Arbor
Université Clermont Auvergne
National Institute for Nuclear Physics
Fakultät Physik
TU Dortmund University
Lamarr Institute for Machine Learning and Artificial Intelligence
Physikalisches Institut
University of Freiburg
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
Institute of Physics
Swiss Federal Institute of Technology Lausanne
Massachusetts Institute of Technology
Laboratoire Leprince-Ringuet
University of Oxford
Heidelberg University

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

Abstract

The first observation of the decay B+→pΛ¯ is presented using proton-proton collision data collected by the LHCb experiment between 2016 and 2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb-1. The signal significance exceeds seven standard deviations. Using the B+→KS0π+ decay as a normalization channel, the branching fraction is measured and combined with previous LHCb results based on data collected at 7 and 8 TeV in 2011 and 2012, yielding B(B+→pΛ¯)=(1.24±0.17±0.05±0.03)×10-7, where the first uncertainty is statistical, the second is systematic, and the third comes from the uncertainty on the branching fraction of the normalization channel. The B+→pΛ¯ weak decay parameter is measured to be αB=0.87-0.29+0.26±0.09, indicating the presence of comparable S-wave and P-wave decay amplitudes.

Original language	English
Article number	051802
Journal	Physical Review Letters
Volume	136
Issue number	5
DOIs	https://doi.org/10.1103/fj4q-t8jg
State	Published - 6 Feb 2026
Externally published	Yes

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10.1103/fj4q-t8jg

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@article{8aa73cc59a5e4c208de55438c63c6eb9,

title = "Observation of the Rare Baryonic Decay B+ →p Λ{\= } and Measurement of its Weak Decay Parameter",

abstract = "The first observation of the decay B+→pΛ¯ is presented using proton-proton collision data collected by the LHCb experiment between 2016 and 2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb-1. The signal significance exceeds seven standard deviations. Using the B+→KS0π+ decay as a normalization channel, the branching fraction is measured and combined with previous LHCb results based on data collected at 7 and 8 TeV in 2011 and 2012, yielding B(B+→pΛ¯)=(1.24±0.17±0.05±0.03){\texttimes}10-7, where the first uncertainty is statistical, the second is systematic, and the third comes from the uncertainty on the branching fraction of the normalization channel. The B+→pΛ¯ weak decay parameter is measured to be αB=0.87-0.29+0.26±0.09, indicating the presence of comparable S-wave and P-wave decay amplitudes.",

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 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} 2026 CERN. ",

year = "2026",

month = feb,

day = "6",

doi = "10.1103/fj4q-t8jg",

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

volume = "136",

journal = "Physical Review Letters",

issn = "0031-9007",

number = "5",

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TY - JOUR

T1 - Observation of the Rare Baryonic Decay B+ →p Λ ̄ and Measurement of its Weak Decay Parameter

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 - 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 - 2026/2/6

Y1 - 2026/2/6

N2 - The first observation of the decay B+→pΛ¯ is presented using proton-proton collision data collected by the LHCb experiment between 2016 and 2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb-1. The signal significance exceeds seven standard deviations. Using the B+→KS0π+ decay as a normalization channel, the branching fraction is measured and combined with previous LHCb results based on data collected at 7 and 8 TeV in 2011 and 2012, yielding B(B+→pΛ¯)=(1.24±0.17±0.05±0.03)×10-7, where the first uncertainty is statistical, the second is systematic, and the third comes from the uncertainty on the branching fraction of the normalization channel. The B+→pΛ¯ weak decay parameter is measured to be αB=0.87-0.29+0.26±0.09, indicating the presence of comparable S-wave and P-wave decay amplitudes.

AB - The first observation of the decay B+→pΛ¯ is presented using proton-proton collision data collected by the LHCb experiment between 2016 and 2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb-1. The signal significance exceeds seven standard deviations. Using the B+→KS0π+ decay as a normalization channel, the branching fraction is measured and combined with previous LHCb results based on data collected at 7 and 8 TeV in 2011 and 2012, yielding B(B+→pΛ¯)=(1.24±0.17±0.05±0.03)×10-7, where the first uncertainty is statistical, the second is systematic, and the third comes from the uncertainty on the branching fraction of the normalization channel. The B+→pΛ¯ weak decay parameter is measured to be αB=0.87-0.29+0.26±0.09, indicating the presence of comparable S-wave and P-wave decay amplitudes.

UR - https://www.scopus.com/pages/publications/105029432496

U2 - 10.1103/fj4q-t8jg

DO - 10.1103/fj4q-t8jg

M3 - Artículo

AN - SCOPUS:105029432496

SN - 0031-9007

VL - 136

JO - Physical Review Letters

JF - Physical Review Letters

IS - 5

M1 - 051802

ER -

Observation of the Rare Baryonic Decay B+ →p Λ ̄ and Measurement of its Weak Decay Parameter

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