Sensitivity of the FCC-ee to the decay of a dark photon into a $\mu^+\mu^-$ pair

Abstract

The production of a dark photon $A^{\prime}$ at the proposed CERN FCC-ee collider is investigated. The study addresses the associated production $e^+e^-\rightarrow\gamma A^{\prime}$ followed by the decay $A^{\prime}\rightarrow\mu^+\mu^-$. The 95% CL sensitivity on the mixing between the photon and the dark photon is evaluated in the $m_{A^{\prime}}$ mass range 0.4-360 GeV, based on a parametrised simulation of the IDEA detector. The study is performed both for prompt and long-lived decays of the $A^{\prime}$.