Search for the rare decay $D^0 \to \mu^+ \mu^-$

TL;DR

This paper reports a search for the rare decay $D^0 o $ using LHCb data, setting a new upper limit that significantly improves previous constraints, with no evidence of the decay observed.

Contribution

The study provides the most stringent upper limit to date on the branching fraction of $D^0 o $, enhancing the sensitivity of rare charm decay searches.

Findings

No significant excess over background observed.

Upper limit on branching fraction set at $6.2 imes 10^{-9}$ (90% CL).

Improved the previous limit by a factor of over twenty.

Abstract

A search for the rare decay $D^0 \to \mu^+ \mu^-$is performed using a data sample, corresponding to an integrated luminosity of 0.9 fb$^{-1}$, of $pp$ collisions collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The observed number of events is consistent with the background expectations and corresponds to an upper limit of \mbox{${\cal B}(D^0 \to \mu^+ \mu^-) < 6.2(7.6) \times 10^{-9}$} at \mbox{90%} \mbox{(95%)} confidence level. This result represents an improvement of more than a factor twenty with respect to previous measurements.