Observation of the decay $B_c^+ \to ψ(2S)π^+$

Abstract

The decay $B_c^+ \to ψ(2S)π^+$ with $ψ(2S) \to μ^+μ^-$ is observed with a significance of $5.2\,σ$ using $pp$ collision data corresponding to an integrated luminosity of $1.0\,\invfb$ collected by the LHCb experiment. The branching fraction of $B_c^+ \to ψ(2S)π^+$ decays relative to that of the $B_c^+ \to J/ψπ^+$ mode is measured to be \begin{equation*} \frac{\mathcal{B}(B_c^+ \to ψ(2S)π^+)}{\mathcal{B}(B_c^+ \to J/ψπ^+)} = 0.250 \pm 0.068 \,\text{stat} \pm 0.014 \,\text{\syst} \pm 0.006 \,(\mathcal{B}). \end{equation*} The last term is the uncertainty on the ratio $\mathcal{B}(ψ(2S) \to μ^+μ^-)/\mathcal{B}(J/ψ\to μ^+μ^-)$.

12 pages including author list, 2 figures