Abstract
The decays $B^+_c \rightarrow J/\psi D_s^+$ and $B^+_c \rightarrow J/\psi D_s^{*+}$ 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 centre-of-mass energies of $\sqrt{s}$=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 $BR(B^+_c \rightarrow J/\psi D_s^+)/BR(B^+_c \rightarrow J/\psi \pi+) = 2.90 \pm 0.57 \pm 0.24$, $BR(B^+_c \rightarrow J/\psi D_s^{*+}) / BR (B^+_c \rightarrow J/\psi D_s^+) = 2.37 \pm 0.56 \pm 0.10$, where the first uncertainties are statistical and the second systematic. The mass of the \Bc meson is measured to be $m_{B^+_c} = 6276.28 \pm 1.44 (stat) \pm 0.36(syst) MeV/c^2$, using the $B^+_c \rightarrow J/\psi D_s^+$ decay mode.
Highlights
The Bþc meson, the ground state of the b"c system, is unique, being the only weakly decaying heavy quarkonium system
The decays Bþc ! J=c Dþs and Bþc ! J=c DÃsþ are observed for the first time using a dataset, corresponding to an integrated luminospityffiffi collisions at center-of-mass energies of s of 1⁄4
The Bþc meson was first observed through its semileptonic decay Bþc ! J=c ‘þ‘X [3]
Summary
The Bþc meson, the ground state of the b"c system, is unique, being the only weakly decaying heavy quarkonium system. Its lifetime [1,2] is almost 3 times smaller than that of other beauty mesons, pointing to the important role of the charm quark in weak Bþc decays. The Bþc meson was first observed through its semileptonic decay Bþc ! Three hadronic modes have been observed so far: Bþc ! The first observations of the decays Bþc ! J=c Dþs is expected to proceed mainly through spectator and color-suppressed spectator diagrams. J=c þ is used as a normalization channel for the measurement of the branching fraction BðBþc ! J=c Dþs mode allows a determination of the Bþc mass with small systematic uncertainty The low energy release (Q value) in the Bþc ! J=c Dþs mode allows a determination of the Bþc mass with small systematic uncertainty
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