Measurements of $B_c^+$ production and mass with the $B_c^+ \to J/\psi \pi^+$ decay

TL;DR

This paper reports precise measurements of the $B_c^+$ meson production rate and mass using the decay $B_c^+ o J/ \, \u03c0^+$ in proton-proton collisions at 7 TeV, providing new insights into heavy meson properties.

Contribution

First measurement of $B_c^+$ production cross-section ratio and mass with the decay mode $B_c^+ o J/ \, \u03c0^+$ at LHCb, improving understanding of heavy meson characteristics.

Findings

$B_c^+$ mass measured to be 6273.7 MeV/c^2.

Production ratio of $B_c^+$ to $B^+$ is approximately 0.68%.

Mass difference between $B_c^+$ and $B^+$ is about 995 MeV/c^2.

Abstract

Measurements of $B_c^+$ production and mass are performed with the decay mode $B_c^+ \to J/\psi \pi^+$ using 0.37 fb$^{-1}$ of data collected in $pp$ collisions at $\sqrt{s}=7$ TeV by the LHCb experiment. The ratio of the production cross-section times branching fraction between the $B_c^+ \to J/\psi \pi^+$ and the $B^+ \to J/\psi K^+$ decays is measured to be $(0.68 \pm 0.10\,({\rm stat.}) \pm 0.03\,({\rm syst.}) \pm 0.05\,({\rm lifetime}))$% for $B_c^+$ and $B^+$ mesons with transverse momenta $p_{\rm T}>4 $GeV/$c$ and pseudorapidities $2.5<\eta<4.5$. The $B_c^+$ mass is directly measured to be $6273.7 \pm 1.3\,({\rm stat.}) \pm 1.6 \,({\rm syst.})$ MeV/$c^2$, and the measured mass difference with respect to the $B^+$ meson is $M(B_c^+)-M(B^+) = 994.6 \pm 1.3\,({\rm stat.}) \pm 0.6\,({\rm syst.})$ MeV/$c^2$.