Abstract
Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1 collected with the LHCb detector, seven decay modes of the {mathrm{B}}_{mathrm{c}}^{+} meson into a J/ψ or ψ(2S) meson and three charged hadrons, kaons or pions, are studied. The decays {mathrm{B}}_{mathrm{c}}^{+} → (ψ(2S) → J/ψπ+π−)π+, {mathrm{B}}_{mathrm{c}}^{+} → ψ(2S)π+π−π+, {mathrm{B}}_{mathrm{c}}^{+} → J/ψK+π−π+ and {mathrm{B}}_{mathrm{c}}^{+} → J/ψK+K−K+ are observed for the first time, and evidence for the {mathrm{B}}_{mathrm{c}}^{+} → ψ(2S)K+K−π+, decay is found, where J/ψ and ψ(2S) mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different {mathrm{B}}_{mathrm{c}}^{+} decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.
Highlights
The decays B+c → (ψ(2S) → J/ψ π+π−)π+, B+c → ψ(2S)π+π−π+, B+c → J/ψ K+π−π+ and B+c → J/ψ K+K−K+ are observed for the first time, and evidence for the B+c → ψ(2S)K+K−π+, decay is found, where J/ψ and ψ(2S) mesons are reconstructed in their dimuon decay modes
Of branching fractions of various B+c → ψ3h± decays, based on this theoretical approach are predicted in refs. [27, 28]
A measurement of the branching fractions of the exclusive B+c meson decays into the final states consisting of charmonium and light hadrons allows for precise tests of the factorisation approach
Summary
The LHCb detector [29, 30] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The online event selection is performed by a trigger [38], which consists of a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage, which performs a full event reconstruction. Decays of unstable particles are described by the EvtGen package [41], in which final-state radiation is generated using Photos [42]. In the B+c → J/ψ K+K−K+ decay several excited K∗+ states are included, with fractions in accordance to the observations described in refs. The interaction of the generated particles with the detector, and its response, are implemented using the Geant toolkit [46, 47] as described in ref. To account for imperfections in the simulation of charged-particle reconstruction, the track-reconstruction efficiency determined from simulation is corrected using calibration samples [49]
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