Observation of the decay $B_c^+ \to \psi(2S)\pi^+$

TL;DR

This paper reports the first observation of the decay $B_c^+ o (2S)\u03C0^+$, measuring its branching ratio relative to $B_c^+ o J/\u03C0^+$, using LHCb data with a significance of 5.2 sigma.

Contribution

The paper provides the first experimental observation and measurement of the branching ratio for the decay $B_c^+ o (2S)C0^+$, expanding knowledge of $B_c^+$ decay modes.

Findings

Decay $B_c^+ o (2S)C0^+$ observed with 5.2 sigma significance.

The ratio of branching fractions is measured to be approximately 0.25.

Results are based on 1.0 fb$^{-1}$ of LHCb collision data.

Abstract

The decay $B_c^+ \to \psi(2S)\pi^+$ with $\psi(2S) \to \mu^+\mu^-$ is observed with a significance of $5.2\,\sigma$ using $pp$ collision data corresponding to an integrated luminosity of $1.0\,\invfb$ collected by the LHCb experiment. The branching fraction of $B_c^+ \to \psi(2S)\pi^+$ decays relative to that of the $B_c^+ \to J/\psi\pi^+$ mode is measured to be \begin{equation*} \frac{\mathcal{B}(B_c^+ \to \psi(2S)\pi^+)}{\mathcal{B}(B_c^+ \to J/\psi\pi^+)} = 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 $\mathcal{B}(\psi(2S) \to \mu^+\mu^-)/\mathcal{B}(J/\psi \to \mu^+\mu^-)$.