Search for the Rare Decay $ {D}^{0}\to {\mu }^{+}{\mu }^{-}$ in Proton-Proton Collisions at $ \sqrt{s}=13.6\text{}\text{}\mathrm{TeV}$

A search for the rare decay $ {D}^{0}\to {\mu }^{+}{\mu }^{-}$ is reported using proton-proton collision events at $ \sqrt{s}=13.6\text{}\text{}\mathrm{TeV}$ collected by the CMS detector in 2022–2023, corresponding to an integrated luminosity of $ 64.5\text{}\text{}{\mathrm{fb}}^{-1}$. This is the first analysis to use a newly developed inclusive dimuon trigger, expanding the scope of the CMS flavor physics program. The search uses $ {D}^{0}$ mesons obtained from $ {D}^{*+}\to {D}^{0}{\pi }^{+}$ decays. No significant excess is observed. A limit on the branching fraction of $ \mathcal{B}({D}^{0}\to {\mu }^{+}{\mu }^{-})<2.4\times {10}^{-9}$ at 95% confidence level is set. This is the most stringent upper limit set on any flavor changing neutral current decay in the charm sector.