Measurement of the ratio of $B_c^+$ branching fractions to $J/\psi\pi^+$ and $J/\psi\mu^+\nu_\mu$

TL;DR

This paper reports the first measurement comparing semileptonic and hadronic decay rates of the $B_c^+$ meson, using LHCb data, providing a ratio that challenges existing theoretical models.

Contribution

It presents the first experimental determination of the ratio between semileptonic and hadronic $B_c^+$ decay branching fractions.

Findings

Measured ratio of branching fractions: 0.0469 ± 0.0028 (stat) ± 0.0046 (syst)

Result is at the lower end of theoretical predictions

Uses 1.0 fb$^{-1}$ of proton-proton collision data

Abstract

The first measurement that relates semileptonic and hadronic decay rates of the $B_c^+$ meson is performed using proton-proton collision data corresponding to 1.0 fb$^{-1}$ of integrated luminosity collected with the LHCb detector. The measured value of the ratio of branching fractions, ${\cal B}(B_c^+ \to J/\psi \pi^+)/{\cal B}(B_c^+\to J/\psi\mu^+\nu_\mu)=0.0469 \pm 0.0028 (stat.) \pm 0.0046 (syst.)$, is at the lower end of available theoretical predictions.