Differential decay rate of B+ → J/ψK+ with the LHCb Upgrade I experiment
A bstract The normalised decay rate of B + → J/ψ (→ μ + μ − ) K + is measured as a function of the lepton helicity angle using a data sample corresponding to an integrated luminosity of 1 . 1 fb − 1 collected during October 2024 with the upgraded (Upgrade I) LHCb detector. This angular distribution can be parameterised by two coefficients, the forward-backward asymmetry, A FB , and the flatness parameter, F H , whose values are constrained by conservation of angular momentum. These coefficients are measured both integrated and differentially across various kinematic and detector-response variables, and the results are found to be in good agreement with expectations. These measurements show that the detector response of the LHCb Upgrade I experiment is understood to the precision required to reliably extract the angular coefficients associated with rare b → sμ + μ − and b → dμ + μ − transitions, which are particularly sensitive to physics beyond the Standard Model.
Authors
- B. Adeva
- W. Baldini (ORCID: https://orcid.org/0000-0001-7658-8777)
- Sergi Bernet Andres
- C. Arata (ORCID: https://orcid.org/0009-0002-1990-7289)
- Alessia Anelli (ORCID: https://orcid.org/0000-0002-6191-934X)
- F. C. R. Bishop (ORCID: https://orcid.org/0000-0002-0023-3897)
- Anna Balboni (ORCID: https://orcid.org/0009-0003-8872-976X)
- Lucio Anderlini
- Maik Becker
- I. Belyaev (ORCID: https://orcid.org/0000-0002-7458-7030)
Institutions
- Eötvös Loránd University (HU)
- Universidade da Coruña (ES)
- Universidade Federal do Rio de Janeiro (BR)
- Uppsala University (SE)
- Centre National de la Recherche Scientifique (FR)
- University of Bonn (DE)
- École Polytechnique (FR)
- University of Liverpool (GB)
- Vilnius University (LT)
- Taras Shevchenko National University of Kyiv (UA)
- Université Clermont Auvergne (FR)
- Lomonosov Moscow State University (RU)
- Universidade de Santiago de Compostela (ES)
- TU Dortmund University (DE)
- Peking University (CN)
- University of Zurich (CH)
- Aix-Marseille Université (FR)
- Heidelberg University (DE)
- University of Cambridge (GB)
- Pontifícia Universidade Católica do Rio de Janeiro (BR)
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR)
- Université Paris-Saclay (FR)
- University of Michigan (US)
- Laboratoire d’Annecy de Physique des Particules (FR)
- Kurchatov Institute (RU)
- CEA Paris-Saclay - Etablissement de Saclay (FR)
- University of Manchester (GB)
- University of Bristol (GB)
- University of Warwick (GB)
- Sorbonne Université (FR)
- University of Oxford (GB)
- National Institute for Subatomic Physics (NL)
- Centre de physique des particules de Marseille (FR)
- Laboratoire de Physique de Clermont Auvergne (FR)
- Laboratoire de Physique Nucléaire et de Hautes Énergies (FR)
- Istituto Nazionale di Fisica Nucleare, Sezione di Padova (IT)
- Institute of Nuclear Physics, Polish Academy of Sciences (PL)
- Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara (IT)
- Istituto Nazionale di Fisica Nucleare, Roma Tor Vergata (IT)
- FZU ‒ Institute of Physics of the Academy of Sciences of the Czech Republic (CZ)
- Centro Brasileiro de Pesquisas Físicas (BR)
- Istituto Nazionale di Fisica Nucleare, Sezione di Genova (IT)
- CEA Paris-Saclay (FR)
- Istituto Nazionale di Fisica Nucleare, Sezione di Firenze (IT)
- Institut National de Physique Nucléaire et de Physique des Particules (FR)
- Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (FR)
- Istituto Nazionale di Fisica Nucleare, Sezione di Milano Bicocca (IT)
- Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati (IT)
- Istituto Nazionale di Fisica Nucleare, Sezione di Bologna (IT)
- Moscow State University (TJ)
- Laboratoire Leprince-Ringuet (FR)
- Istituto Nazionale di Fisica Nucleare, Sezione di Roma I (IT)
- Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT)
- University of Chinese Academy of Sciences (CN)
- Institut de Recherche sur les Lois Fondamentales de l'Univers (FR)
- Consejo Nacional de Rectores
- Imperial College London (GB)
- École Polytechnique Fédérale de Lausanne (CH)
- Universitat Ramon Llull (ES)
- Massachusetts Institute of Technology (US)
- European Organization for Nuclear Research (CH)
- AGH University of Krakow (PL)
- Université Savoie Mont Blanc (FR)
- Syracuse University (US)
- Ruhr University Bochum (DE)
- University of Edinburgh (GB)
Publication Details
- Journal
- Journal of High Energy Physics
- Published
- 2026-04-22
- DOI
- https://doi.org/10.1007/jhep04(2026)170
- Primary Topic
- Particle physics theoretical and experimental studies
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- U.S. Department of Energy
- CERN
- UK Research and Innovation
- Institutul National de Cercetare-Dezvoltare pentru Fizica si Inginerie Nucleara 'Horia Hulubei'
- Leverhulme Trust
- European Commission
- Deutsche Forschungsgemeinschaft
- Agence Nationale de la Recherche
- Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
- National Natural Science Foundation of China
- Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek
- Ministerio de Economía y Competitividad
- Generalitat Valenciana
- Conselho Nacional de Desenvolvimento Científico e Tecnológico
- Max-Planck-Gesellschaft
- Ministerstwo Edukacji i Nauki
- Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
- National Academy of Sciences of Ukraine
- Centre National de la Recherche Scientifique
- Financiadora de Estudos e Projetos
- Région Auvergne-Rhône-Alpes
- CAS Center for Excellence in Particle Physics
- Australian Research Data Commons
- Science and Technology Facilities Council
- Deutsches Elektronen-Synchrotron
- Agencia Estatal de Investigación
- Institute of High Energy Physics
- Institut National de Physique Nucléaire et de Physique des Particules
- Nuclear Physics
- H2020 Marie Skłodowska-Curie Actions