Measurement of the branching fraction ratio $\mathcal{B}(B_c^{+}\to \psi (2S){\pi }^{+})\mathrm{/}\mathcal{B}(B_c^{+}\to J\mathrm{/}\psi {\pi }^{+})$

Using $pp$ collision data collected by LHCb at center-of-mass energies $\sqrt{s}$ = 7 TeV and 8 TeV, corresponding to an integrated luminosity of 3 fb${}^{-1}$, the ratio of the branching fraction of the $B_c^+ \rightarrow \psi(2S)\pi^+$decayrelativetothatofthe$B_c^+ \rightarrow J/\psi\pi^+$decayismeasuredtobe0.268$\pm$0.032(stat)$\pm$0.007(syst)$\pm$ 0.006 (BF). The first uncertainty is statistical, the second is systematic, and the third is due to the uncertainties on the branching fractions of the $J/\psi \rightarrow \mu^+\mu^-$and$\psi(2S) \rightarrow \mu^+\mu^-$ decays. This measurement is consistent with the previous LHCb result, and the statistical uncertainty is halved.