Badalov, AlexeyCalvo Gómez, MíriamGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarin Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséRuiz, Hugo (Ruiz Pérez)Vilasis-Cardona, XavierLHCb Collaboration2019-05-092019-05-092015-09-090031-9007https://hdl.handle.net/2445/132872The branching fraction ratio R ( D ∗ ) ≡ B ( ¯ B 0 → D * + τ − ¯ ν τ ) / B ( ¯ B 0 → D * + μ − ¯ ν μ ) is measured using a sample of proton-proton collision data corresponding to 3.0     fb − 1 of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ − → μ − ¯ ν μ ν τ . The semitauonic decay is sensitive to contributions from non-standard-model particles that preferentially couple to the third generation of fermions, in particular, Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate ¯ B 0 decays gives R ( D ∗ ) = 0.336 ± 0.027 ( stat ) ± 0.030 ( syst ) . This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the standard model.10 p.application/pdfengcc by (c) CERN; LHCb Collaboration, 2015http://creativecommons.org/licenses/by/3.0/es/Física de partículesExperimentsParticle physicsExperimentsinfo:eu-repo/semantics/article6567742019-05-09info:eu-repo/semantics/openAccess