Search for the rare decay D0 -> mu+ mu- in proton-proton collisions at sqrt(s) = 13.6 TeV

A search for the rare decay 𝐷0→𝜇+⁢𝜇− is reported using proton-proton collision events at √𝑠 =13.6  TeV collected by the CMS detector in 2022–2023, corresponding to an integrated luminosity of 64.5  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 𝐷0 mesons obtained from 𝐷*+→𝐷0⁢𝜋+ decays. No significant excess is observed. A limit on the branching fraction of ℬ⁡(𝐷0→𝜇+⁢𝜇−)<2.4×10−9 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.