Abellan Beteta, CarlosCalvo Gómez, MíriamCamboni, AlessandroComerma Montells, AlbertGarrido Beltrán, LluísGraciani Díaz, RicardoGraugés Pous, EugeniLópez Asamar, EliasOyanguren Campos, Arantza dePérez-Calero Yzquierdo, AntonioPicatoste Olloqui, EduardoPotterat, CédricRives Molina, Vicente JoséRuiz, Hugo (Ruiz Pérez)Ruiz Valls, PabloVázquez Gómez, RicardVilasis-Cardona, XavierLHCb Collaboration2019-04-082019-04-082013-06-281550-7998https://hdl.handle.net/2445/131841The decays B + c → J / ψ D + s and B + c → J / ψ D * + s are observed for the first time using a dataset, corresponding to an integrated luminosity of 3     fb − 1 , collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of √ s = 7 and 8 TeV. The statistical significance for both signals is in excess of 9 standard deviations. The following ratios of branching fractions are measured to be B ( B + c → J / ψ D + s ) B ( B + c → J / ψ π + ) = 2.90 ± 0.57 ± 0.24 , B ( B + c → J / ψ D * + s ) B ( B + c → J / ψ D + s ) = 2.37 ± 0.56 ± 0.10 , where the first uncertainties are statistical and the second systematic. The mass of the B + c meson is measured to be m B + c = 6276.28 ± 1.44 ( stat ) ± 0.36 ( syst )     MeV / c 2 , using the B + c → J / ψ D + s decay mode.10 p.application/pdfengcc by (c) CERN; LHCb Collaboration, 2013http://creativecommons.org/licenses/by/3.0/es/Física de partículesExperimentsParticle physicsExperimentsinfo:eu-repo/semantics/article6289992019-04-08info:eu-repo/semantics/openAccess