Search for $B_{(s)}^{*0}\to\mu^+\mu^-$ in $B_c^+\to\pi^+\mu^+\mu^-$ decays

TL;DR

This paper reports a search for rare $B^{*0}$ and $B_s^{*0}$ decays into muon pairs within $B_c^+$ decays using LHCb data, setting upper limits due to no observed excess.

Contribution

It provides the first experimental upper limits on these rare decay modes using a large dataset from the LHCb detector.

Findings

No significant signal observed for either decay mode.

Upper limits set on branching fraction ratios at 90% confidence level.

Results constrain new physics models predicting these rare decays.

Abstract

A search for the very rare $B^{*0}\to\mu^+\mu^-$ and $B_{s}^{*0}\to\mu^+\mu^-$ decays is conducted by analysing the $B_c^+\to \pi^+\mu^+\mu^-$ process. The analysis uses proton-proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9$\text{\,fb}^{-1}$. The signal signatures correspond to simultaneous peaks in the $\mu^+\mu^-$ and $\pi^+\mu^+\mu^-$ invariant masses. No evidence for an excess of events over background is observed for either signal decay mode. Upper limits at the $90\%$ confidence level are set on the branching fractions relative to that for $B_c^+\to J\mskip -3mu/\mskip -2mu\psi\pi^+$ decays, \begin{equation*} {\cal R}_{B^{*0}(\mu^+\mu^-)\pi^+/J\mskip -3mu/\mskip -2mu\psi\pi^+} < 3.8\times 10^{-5}\ \text{ and }\: {\cal R}_{B_{s}^{*0}(\mu^+\mu^-)\pi^+/J\mskip -3mu/\mskip -2mu\psi\pi^+} < 5.0\times 10^{-5}\,. \end{equation*}