Measurement of the Ratio of the B0 →d∗-τ+ντ and B0 →d∗-μ+νμ Branching Fractions Using Three-Prong τ -Lepton Decays

LHCb Collaboration

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The ratio of branching fractions R(D∗-)≡B(B0→D∗-τ+ντ)/B(B0→D∗-μ+νμ) is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb-1. For the first time, R(D∗-) is determined using the τ-lepton decays with three charged pions in the final state. The B0→D∗-τ+ντ yield is normalized to that of the B0→D∗-π+π-π+ mode, providing a measurement of B(B0→D∗-τ+ντ)/B(B0→D∗-π+π-π+)=1.97±0.13±0.18, where the first uncertainty is statistical and the second systematic. The value of B(B0→D∗-τ+ντ)=(1.42±0.094±0.129±0.054)% is obtained, where the third uncertainty is due to the limited knowledge of the branching fraction of the normalization mode. Using the well-measured branching fraction of the B0→D∗-μ+νμ decay, a value of R(D∗-)=0.291±0.019±0.026±0.013 is established, where the third uncertainty is due to the limited knowledge of the branching fractions of the normalization and B0→D∗-μ+νμ modes. This measurement is in agreement with the standard model prediction and with previous results.

Original languageEnglish
Article number171802
JournalPhysical Review Letters
Issue number17
Publication statusPublished - 25 Apr 2018


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); MinES and FASO (Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); NSF (USA). 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 (USA). 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), ANR, Labex P2IO, ENIGMASS and OCEVU, and Région Auvergne-Rhóne-Alpes (France), RFBR and Yandex LLC (Russia), GVA, XuntaGal, and GENCAT (Spain), and Herchel Smith Fund, the Royal Society, the English-Speaking Union, and the Leverhulme Trust (United Kingdom).

FundersFunder number
Not addedST/J004332/1, ST/N000250/1, 1681016, ST/K003410/1, 1796908, ST/H006737/1, ST/N000463/1, ST/L003163/1, ST/N000242/1
AvH Foundation
Herchel Smith Fund
Région Auvergne-Rhóne-Alpes
Yandex LLC
National Science Foundation
School of Energy Resources, University of Wyoming
H2020 Marie Skłodowska-Curie Actions
Science and Technology Facilities CouncilLHCb, GRIDPP, LHCb Upgrades, ST/N000455/1
Leverhulme Trust
Royal Society
European Commission
European Research Council
Deutsche Forschungsgemeinschaft
Agence Nationale de la Recherche
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung166208
National Natural Science Foundation of China
Russian Foundation for Basic Research
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Bundesministerium für Bildung und Forschung
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Generalitat Valenciana
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Ministry of Science and Technology
Instituto Nazionale di Fisica Nucleare
Narodowe Centrum Nauki
Ministerstwo Nauki i Szkolnictwa Wyższego
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
National Academy of Sciences of Ukraine
Financiadora de Estudos e Projetos


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