Displaced Vertex

We show that MUonE can also discover thermal relic dark matter using only its nominal experimental setup. Furthermore, our results show that the downstream ECAL plays a key role in rejecting backgrounds for this search, thereby providing strong motivation for the MUonE to keep this component in the final experimental design.

We demonstrate how to search for dark photons by displaced vertex search at the proposed MUonE experiment 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 $\mu^{\pm}, e^- \to \mu^{\pm}, e^-, A’$ followed by $A’\to e^+e^-$.