Observation of the and decays

doi:10.1140/epjc/s10052-025-14129-6

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2025) 85: 812
https://doi.org/10.1140/epjc/s10052-025-14129-6

Regular Article - Experimental Physics

Observation of the $Λ_{b}^{0} \to J / ψ Ξ^{-} K^{+}$ ${{{\varLambda } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{K} ^+} }$ and $Ξ_{b}^{0} \to J / ψ Ξ^{-} π^{+}$ ${{{{\varXi } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{\pi } ^+} }}$ decays

LHCb Collaboration¹¹³^a

¹ School of Physics and Astronomy, Monash University, Melbourne, Australia
² Centro Brasileiro de Pesquisas Físicas (CBPF), Rio de Janeiro, Brazil
³ Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
⁴ Department of Engineering Physics, Tsinghua University, Beijing, China
⁵ Institute of High Energy Physics (IHEP), Beijing, China
⁶ School of Physics State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China
⁷ University of Chinese Academy of Sciences, Beijing, China
⁸ Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China
⁹ Consejo Nacional de Rectores (CONARE), San Jose, Costa Rica
¹⁰ Université Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France
¹¹ Université Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France
¹² Université Paris-Saclay, Centre d?‘Etudes de Saclay (CEA), IRFU, Saclay, Gif-sur-Yvette, France
¹³ Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France
¹⁴ Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
¹⁵ Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
¹⁶ LPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3, Paris, France
¹⁷ I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany
¹⁸ Universität Bonn-Helmholtz-Institut für Strahlen und Kernphysik, Bonn, Germany
¹⁹ Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany
²⁰ Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
²¹ Max-Planck-Institut für Kernphysik (MPIK), Heidelberg, Germany
²² Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
²³ School of Physics, University College Dublin, Dublin, Ireland
²⁴ INFN Sezione di Bari, Bari, Italy
²⁵ INFN Sezione di Bologna, Bologna, Italy
²⁶ INFN Sezione di Ferrara, Ferrara, Italy
²⁷ INFN Sezione di Firenze, Firenze, Italy
²⁸ INFN Laboratori Nazionali di Frascati, Frascati, Italy
²⁹ INFN Sezione di Genova, Genoa, Italy
³⁰ INFN Sezione di Milano, Milan, Italy
³¹ INFN Sezione di Milano-Bicocca, Milan, Italy
³² INFN Sezione di Cagliari, Monserrato, Italy
³³ INFN Sezione di Padova, Padua, Italy
³⁴ INFN Sezione di Perugia, Perugia, Italy
³⁵ INFN Sezione di Pisa, Pisa, Italy
³⁶ INFN Sezione di Roma La Sapienza, Rome, Italy
³⁷ INFN Sezione di Roma Tor Vergata, Rome, Italy
³⁸ Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands
³⁹ Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, The Netherlands
⁴⁰ AGH-University of Krakow, Faculty of Physics and Applied Computer Science, Kraków, Poland
⁴¹ Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland
⁴² National Center for Nuclear Research (NCBJ), Warsaw, Poland
⁴³ Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania
⁴⁴ Affiliated with an Institute Covered by a Cooperation Agreement with CERN, Geneva, Switzerland
⁴⁵ DS4DS, La Salle, Universitat Ramon Llull, Barcelona, Spain
⁴⁶ ICCUB, Universitat de Barcelona, Barcelona, Spain
⁴⁷ Instituto Galego de Física de Altas Enerxías (IGFAE), Universidade de Santiago de Compostela, Santiago de Compostela, Spain
⁴⁸ Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia-CSIC, Valencia, Spain
⁴⁹ European Organization for Nuclear Research (CERN), Geneva, Switzerland
⁵⁰ Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
⁵¹ Physik-Institut, Universität Zürich, Zurich, Switzerland
⁵² NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine
⁵³ Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine
⁵⁴ School of Physics and Astronomy, University of Birmingham, Birmingham, UK
⁵⁵ H.H. Wills Physics Laboratory, University of Bristol, Bristol, UK
⁵⁶ Cavendish Laboratory, University of Cambridge, Cambridge, UK
⁵⁷ Department of Physics, University of Warwick, Coventry, UK
⁵⁸ STFC Rutherford Appleton Laboratory, Didcot, UK
⁵⁹ School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
⁶⁰ School of Physics and Astronomy, University of Glasgow, Glasgow, UK
⁶¹ Oliver Lodge Laboratory, University of Liverpool, Liverpool, UK
⁶² Imperial College London, London, UK
⁶³ Department of Physics and Astronomy, University of Manchester, Manchester, UK
⁶⁴ Department of Physics, University of Oxford, Oxford, UK
⁶⁵ Massachusetts Institute of Technology, Cambridge, MA, USA
⁶⁶ University of Cincinnati, Cincinnati, OH, USA
⁶⁷ University of Maryland, College Park, MD, USA
⁶⁸ Los Alamos National Laboratory (LANL), Los Alamos, NM, USA
⁶⁹ Syracuse University, Syracuse, NY, USA
⁷⁰ Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil
⁷¹ School of Physics and Electronics, Hunan University, Changsha, China
⁷² Guangdong Provincial Key Laboratory of Nuclear Science, Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Institute of Quantum Matter, South China Normal University, Guangzhou, China
⁷³ Lanzhou University, Lanzhou, China
⁷⁴ School of Physics and Technology, Wuhan University, Wuhan, China
⁷⁵ Departamento de Fisica, Universidad Nacional de Colombia, Bogota, Colombia
⁷⁶ Ruhr Universitaet Bochum, Fakultaet f. Physik und Astronomie, Bochum, Germany
⁷⁷ Eotvos Lorand University, Budapest, Hungary
⁷⁸ Van Swinderen Institute, University of Groningen, Groningen, The Netherlands
⁷⁹ Universiteit Maastricht, Maastricht, The Netherlands
⁸⁰ Tadeusz Kosciuszko Cracow University of Technology, Cracow, Poland
⁸¹ Universidade da Coruña, A Coruña, Spain
⁸² Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
⁸³ Taras Schevchenko University of Kyiv, Faculty of Physics, Kyiv, Ukraine
⁸⁴ University of Michigan, Ann Arbor, MI, USA
⁸⁵ Ohio State University, Columbus, USA
⁸⁶ Centro Federal de Educacão Tecnológica Celso Suckow da Fonseca, Rio De Janeiro, Brazil
⁸⁷ Center for High Energy Physics, Tsinghua University, Beijing, China
⁸⁸ Hangzhou Institute for Advanced Study, UCAS, Hangzhou, China
⁸⁹ School of Physics and Electronics, Henan University, Kaifeng, China
⁹⁰ LIP6, Sorbonne Université, Paris, France
⁹¹ Lamarr Institute for Machine Learning and Artificial Intelligence, Dortmund, Germany
⁹² Universidad Nacional Autónoma de Honduras, Tegucigalpa, Honduras
⁹³ Università di Bari, Bari, Italy
⁹⁴ Università di Bergamo, Bergamo, Italy
⁹⁵ Università di Bologna, Bologna, Italy
⁹⁶ Università di Cagliari, Cagliari, Italy
⁹⁷ Università di Ferrara, Ferrara, Italy
⁹⁸ Università di Genova, Genoa, Italy
⁹⁹ Università degli Studi di Milano, Milan, Italy
¹⁰⁰ Università degli Studi di Milano-Bicocca, Milan, Italy
¹⁰¹ Università di Padova, Padua, Italy
¹⁰² Università di Perugia, Perugia, Italy
¹⁰³ Scuola Normale Superiore, Pisa, Italy
¹⁰⁴ Università di Pisa, Pisa, Italy
¹⁰⁵ Università della Basilicata, Potenza, Italy
¹⁰⁶ Università di Roma Tor Vergata, Rome, Italy
¹⁰⁷ Università di Siena, Siena, Italy
¹⁰⁸ Università di Urbino, Urbino, Italy
¹⁰⁹ Universidad de Ingeniería y Tecnología (UTEC), Lima, Peru
¹¹⁰ Universidad de Alcalá, Alcalá de Henares, Spain
¹¹¹ Facultad de Ciencias Fisicas, Madrid, Spain
¹¹² Department of Physics/Division of Particle Physics, Lund, Sweden
¹¹³ CERN, 1211, Geneva 23, Switzerland

^a luis.miguel.garcia.martin@cern.ch

Received: 24 January 2025
Accepted: 26 March 2025
Published online: 28 July 2025

Abstract

The first observation of the $Ξ_{b}^{0} \to J / ψ Ξ^{-} π^{+}$ ${{{{\varXi } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{\pi } ^+} }}$ decay and the most precise measurement of the branching fraction of the $Λ_{b}^{0} \to J / ψ Ξ^{-} K^{+}$ ${{{\varLambda } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{K} ^+} }$ decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016–2018 at a centre-of-mass energy of 13 $\,Te V$ $\text {\,Te\hspace{-1.00006pt}V}$ , corresponding to an integrated luminosity of 5.4 ${\,fb}^{- 1}$ $\text {\,fb} ^{-1}$ . Using the $Λ_{b}^{0} \to J / ψ Λ$ ${{{{\varLambda } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {\varLambda } }}$ and $Ξ_{b}^{-} \to J / ψ Ξ^{-}$ ${{{{\varXi } ^-_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} }}$ decays as normalisation channels, the ratios of branching fractions are measured to be $\begin{matrix} \frac{B (Λ_{b}^{0} \to J / ψ Ξ^{-} K^{+})}{B (Λ_{b}^{0} \to J / ψ Λ)} & = (1.17 \pm 0.14 \pm 0.08) \times 10^{- 2}, \\ \frac{B (Ξ_{b}^{0} \to J / ψ Ξ^{-} π^{+})}{B (Ξ_{b}^{-} \to J / ψ Ξ^{-})} & = (11.9 \pm 1.4 \pm 0.6) \times 10^{- 2}, \end{matrix}$ $\begin{aligned} {\frac{{{\mathcal {B}}}({{{\varLambda } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{K} ^+} })}{{{\mathcal {B}}}({{{{\varLambda } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {\varLambda } }})}}&= (1.17 \pm 0.14 \pm 0.08)\times 10^{-2} \, ,\\ {\frac{{{\mathcal {B}}}({{{{\varXi } ^0_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} {{\pi } ^+} }})}{{{\mathcal {B}}}({{{{\varXi } ^-_{b}} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\varXi } ^-} }})}}&= (11.9 \pm 1.4 \pm 0.6)\times 10^{-2}\, , \end{aligned}$ where the first uncertainty is statistical and the second systematic.

A. B. Gonzalo.

© CERN for the benefit of the LHCb collaboration 2025

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