Search for the Rare Decay 𝐷° → 𝜇⁺⁢𝜇⁻ in Proton-Proton Collisions at √𝒔 = 13.6 TeV

Abstract

A search for the rare decay 𝐷° → 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 𝐷° mesons obtained from 𝐷*⁺ → 𝐷°𝜋⁺ decays. No significant excess is observed. A limit on the branching fraction of ℬ(𝐷° → 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.