Dark Photons and Displaced Vertices at the MUonE Experiment

Iftah Galon, David Shih, Isaac R. Wang

Published 2022-02-17Version 1

MUonE is a proposed experiment designed to measure the hadronic vacuum polarization contribution to muon $g-2$ through elastic $\mu-e$ scattering. As such it employs an extremely high-resolution tracking apparatus. We point out that this makes MUonE also a very promising experiment to search for displaced vertices from light, weakly-interacting new particles. We demonstrate its potential by showing how it has excellent sensitivity to dark photons in the mass range $10~\mathrm{Mev} \le m_{A'} \le 100~\mathrm{MeV}$ and kinetic mixing parameter $10^{-5} \le \epsilon e \le 10^{-3}$, through the process $\mu^-\, e^- \to \mu^-\, e^-\, A'$ followed by $A'\to e^+e^-$.