First Observation of the Decay Bs0K-μ+νμ and a Measurement of |Vub | / |Vcb |

Research output: Contribution to journalArticlepeer-review


  • LHCb Collaboration

Colleges, School and Institutes

External organisations

  • Nikhef National Institute for Subatomic Physics
  • University of Zurich
  • University of Liverpool
  • Universidad de Santiago de Compostela
  • University of Bristol
  • Université Clermont Auvergne
  • University of Michigan
  • Istituto Nazionale di Fisica Nucleare, Sezione di Milano
  • University of Cincinnati
  • TU Dortmund University, Germany
  • CERN
  • University of Glasgow
  • Universitat Autonoma de Barcelona
  • University of Manchester
  • Petersburg Nuclear Physics Institute (PNPI)
  • Universidade Federal Do Rio de Janeiro
  • Paris-Saclay University
  • Sezione INFN di Firenze
  • Sezione INFN di Ferrara
  • Ruprecht-Karls-Universität Heidelberg
  • Institute for High Energy Physics (IHEP)
  • Syracuse University
  • Yandex School of Data Analysis
  • IN2P3
  • Laboratoire Leprince-Ringuet
  • Ecole Polytechnique Federale de Lausanne
  • University of Warwick
  • Imperial College London
  • Sezione di Perugia
  • Instituto Galego de Física de Altas Enerxías (IGFAE)
  • Chinese Academy of Sciences


The first observation of the suppressed semileptonic Bs0 →K-μ+νμ decay is reported. Using a data sample recorded in pp collisions in 2012 with the LHCb detector, corresponding to an integrated luminosity of 2 fb-1, the branching fraction B(Bs0 →K-μ+νμ ) is measured to be [1.06±0.05(stat)±0.08(syst)]×10-4, where the first uncertainty is statistical and the second one represents the combined systematic uncertainties. The decay Bs0 →Ds-μ+νμ, where Ds- is reconstructed in the final state K+K-π-, is used as a normalization channel to minimize the experimental systematic uncertainty. Theoretical calculations on the form factors of the Bs0K- and Bs0Ds- transitions are employed to determine the ratio of the Cabibbo-Kobayashi-Maskawa matrix elements |Vub|/|Vcb| at low and high Bs0K- momentum transfer.

Bibliographic note

Funding Information: We express our gratitude to our colleagues in the CERN accelerator departments for the excellent performance of the LHC. We thank the technical and administrative staff at the LHCb institutes. We acknowledge support from CERN and from the national agencies CAPES, CNPq, FAPERJ, and FINEP (Brazil), MOST and NSFC (China), CNRS/IN2P3 (France), BMBF, DFG, and MPG (Germany), INFN (Italy), NWO (Netherlands), MNiSW and NCN (Poland), MEN/IFA (Romania), MSHE (Russia), MICINN (Spain), SNSF and SER (Switzerland), NASU (Ukraine), STFC (United Kingdom), and DOE NP and NSF (US). We acknowledge the computing resources that are provided by CERN, IN2P3 (France), KIT and DESY (Germany), INFN (Italy), SURF (Netherlands), PIC (Spain), GridPP (United Kingdom), RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH (Romania), CBPF (Brazil), PL-GRID (Poland), and OSC (US). We are indebted to the communities behind the multiple open-source software packages on which we depend. Individual groups or members have received support from AvH Foundation (Germany), EPLANET, Marie Skłodowska-Curie Actions, and ERC (European Union), A*MIDEX, ANR, Labex P2IO, and OCEVU, and Région Auvergne-Rhône-Alpes (France), Key Research Program of Frontier Sciences of CAS, CAS PIFI, CAS CCEPP, Fundamental Research Funds for Central Universities, and Sci. and Tech. Program of Guangzhou (China), RFBR, RSF, and Yandex LLC (Russia), GVA, XuntaGal, and GENCAT (Spain), and the Royal Society and the Leverhulme Trust (United Kingdom).


Original languageEnglish
Article number081804
JournalPhysical Review Letters
Issue number8
Publication statusPublished - 25 Feb 2021

ASJC Scopus subject areas