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
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
Vilnius University
CERN
University of Cambridge
Sorbonne Université
Universidade Federal do Rio de Janeiro
Peking University
University of A Coruna
University of Chinese Academy of Sciences
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
Eötvös Loránd University
Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences
University of Bonn
Imperial College London
Université Savoie Mont Blanc
Los Alamos National Laboratory
Maastricht University
Monash University
Cracow University of Technology
Ohio State University
Wuhan University
University of Barcelona
Tsinghua University
NASU - Institute of Nuclear Research
Horia Hulubei National Institute of Physics and Nuclear Engineering
University of Glasgow
University of Cincinnati
University of Groningen
Central China Normal University
University College Dublin
South China Normal University
Rutherford Appleton Laboratory
University of Valencia
University of Maryland, College Park
NASU - Kharkov Institute of Physics and Technology
University of Freiburg
National Centre for Nuclear Research
RWTH Aachen University
Universidad Nacional de Colombia
Czech Academy of Sciences
University of Birmingham
Vrije Universiteit Amsterdam
Henan Normal University
Lanzhou University
Hunan University
Max Planck Institute for Nuclear Physics
Universidad Andrés Bello

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)×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",

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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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