First observation of the decay B+c→J/ψπ+π−π+

Author(s): Aaij, R; Beteta, CA; Adeva, B; Adinolfi, M; Adrover, C; Affolder, A; Ajaltouni, Z; Albrecht, J; Alessio, F; Alexander, M; Ali, S; Alkhazov, G; Cartelle, PA; Alves, AA; Amato, S; Amerio, S; Amhis, Y; Anderlini, L; Anderson, J; Andreassen, R; Appleby, RB; Gutierrez, OA; Archilli, F; Artamonov, A; Artuso, M; Aslanides, E; Auriemma, G; Bachmann, S; Back, JJ; Baesso, C; Balagura, V; Baldini, W; Barlow, RJ; Barschel, C; Barsuk, S; Barter, W; Bauer, T; Bay, A; Beddow, J; Bedeschi, F; Bediaga, I; Belogurov, S; Belous, K; Belyaev, I; Ben-Haim, E; Bencivenni, G; Benson, S; Benton, J; Berezhnoy, A; Bernet, R; Bettler, MO; Van Beuzekom, M; Bien, A; Bifani, S; Bird, T; Bizzeti, A; Bjornstad, PM; Blake, T; Blanc, F; Blouw, J; Blusk, S; Bocci, V; Bondar, A; Bondar, N; Bonivento, W; Borghi, S; Borgia, A; Bowcock, TJV; Bowen, E; Bozzi, C; Brambach, T; Van Den Brand, J; Bressieux, J; Brett, D; Britsch, M; Britton, T; Brook, NH; Brown, H; Burducea, I; Bursche, A; Busetto, G; Buytaert, J; Cadeddu, S; Callot, O; Calvi, M | Abstract: The decay Bc+to → J/ψ K+ is observed for the first time using a data sample, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. A yield of 46 ± 12 events is reported, with a significance of 5.0 standard deviations. The ratio of the branching fraction of Bc+to → J/ψ K+ to that of Bc+to → J/ψ K+ is measured to be 0.069 ± 0.019 ± 0.005, where the first uncertainty is statistical and the second is systematic. © 2013 Cern for the benefit of the LHCb collaboration.