Eur. Phys. J. C (2025) 85: 20
https://doi.org/10.1140/epjc/s10052-024-13573-0

Regular Article - Experimental Physics

Search for $B_{(s)}^{\ast 0}\to {\mu }^{+}{\mu }^{-}$ in $B_c^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-}$ decays

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

^a fernando.abudinen@cern.ch

Received: 27 September 2024
Accepted: 5 November 2024
Published online: 13 January 2025

Abstract

A search for the very rare $B_{}^{\ast 0}\to {\mu }^{+}{\mu }^{-}$ and $B_s^{\ast 0}\to {\mu }^{+}{\mu }^{-}$ decays is conducted by analysing the $B_c^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-}$ process. The analysis uses proton-proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9${\text{,fb}}^{-1}$. The signal signatures correspond to simultaneous peaks in the ${\mu }^{+}{\mu }^{-}$ and ${\pi }^{+}{\mu }^{+}{\mu }^{-}$ invariant masses. No evidence for an excess of events over background is observed for either signal decay mode. Upper limits at the $90\%$ confidence level are set on the branching fractions relative to that for $B_c^{+}\to J/\psi {\pi }^{+}$ decays, $$\begin{array}{cc}\hfill \mathcal{R}_{B_{}^{\ast 0}({\mu }^{+}{\mu }^{-}){\pi }^{+}/J/\psi {\pi }^{+}}^{}& <3.8\times {10}^{-5}\text{and}\hfill \\ \hfill \mathcal{R}_{B_s^{\ast 0}({\mu }^{+}{\mu }^{-}){\pi }^{+}/J/\psi {\pi }^{+}}^{}& <5.0\times {10}^{-5}.\hfill \end{array}$$