Search for a low mass dark photon radiated from a muon*

A search for dark photons with mass below 1 MeV, radiated from a final state muon, is presented using proton-proton collision data collected with the CMS detector in 2018, at a center-of-mass energy of 13 TeV. A low mass dark photon has no available decay channel to standard model particles, and is hence stable. We assume that a dark photon directly interacts with detector materials through virtual pair-production. Its small kinetic mixing with the Standard Model photon allows a dark photon to penetrate the CMS electromagnetic calorimeter and deposit energy in the hadronic calorimeter. The search is performed by looking for events whose final state is composed of two muons and a photon-like shower in hadronic Calorimeter. Preliminary studies about distinguishing the signal from the standard model backgrounds will be presented.