First observation of the decay $B_{c}^{+}\to J/\psi K^+$

TL;DR

This paper reports the first observation of the decay $B_c^+ o J/ K^+$, measuring its branching ratio relative to $B_c^+ o J/ \u03c0^+$ using LHCb data, with a significance of 5 sigma.

Contribution

The paper presents the first experimental observation of the decay $B_c^+ o J/ K^+$ and measures its branching fraction ratio, expanding understanding of $B_c^+$ decay modes.

Findings

First observation of $B_c^+ o J/ K^+$ decay.

Branching fraction ratio $0.069 \u00b1 0.019 \u00b1 0.005$.

Significance of 5.0 standard deviations.

Abstract

The decay $B_c^+\to J/\psi K^+$ is observed for the first time using a data sample, corresponding to an integrated luminosity of 1.0 ${\,fb}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a centre-of-mass energy of $7\mathrm{\,Te\kern -0.1em V}$. A yield of $46\pm12$ events is reported, with a significance of 5.0 standard deviations. The ratio of the branching fraction of $B_c^+\to J/\psi K^+$ to that of $B_c^+\to J/\psi\pi^+$ is measured to be $0.069\pm0.019\pm0.005$, where the first uncertainty is statistical and the second is systematic.