Observation of the decay $B_c^{+}\to \ddot{I}ˆ(2S)\ddot{I}{€}^{+}$

Abstract

The decay $B_c^{+}\to \ddot{I}ˆ(2S)\ddot{I}{€}^{+}$ with $\ddot{I}ˆ(2S)\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}$ is observed with a significance of $5.2\ddot{I}ƒ$ using $pp$ collision data corresponding to an integrated luminosity of $1.0\,\invfb$ collected by the LHCb experiment. The branching fraction of $B_c^{+}\to \ddot{I}ˆ(2S)\ddot{I}{€}^{+}$ decays relative to that of the $B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{€}^{+}$ 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 $\mathcal{B}(\ddot{I}ˆ(2S)\to \hat{I}{¼}^{+}\hat{I}{¼}^{-})/\mathcal{B}(J/\ddot{I}ˆ\to \hat{I}{¼}^{+}\hat{I}{¼}^{-})$.

12 pages including author list, 2 figures