# Combined search for light dark matter with electron and muon beams at NA64

## TL;DR

This paper explores how combined electron and muon beam experiments at NA64 can effectively search for light dark matter mediated by a dark photon, covering significant parameter space and enhancing discovery potential.

## Contribution

It demonstrates the potential of combined NA64e and NA64μ results to probe light dark matter models more comprehensively than individual experiments.

## Key findings

- NA64e can probe scalar and Majorana LDM scenarios with 5×10^{12} EOT.
- Combined NA64e and NA64μ results with ~10^{13} EOT and 10^{13} MOT cover significant LDM parameter space.
- NA64e and NA64μ are highly complementary, increasing discovery potential for sub-GeV dark matter.

## Abstract

We discuss prospects of searching for a dark photon ($A'$) which serves as mediator between Standard model (SM) particles and light dark matter (LDM) by using the combined results from the NA64 experiment at the CERN SPS running in high-energy electron (NA64e) and muon (NA64$\mu$) modes. We discuss the most natural values and upper bounds on the $A'$ coupling constant to LDM and show they are lying in the range accessible at NA64. While for the projected $ 5\times10^{12}$ electrons on target (EOT) NA64e is able to probe the scalar and Majorana LDM scenarios, the combined NA64e and NA64$\mu$ results with $\simeq 10^{13}$ EOT and a few $10^{13}$ MOT, respectively, will allow covering significant region in the parameter space of the most interesting LDM models. This makes NA64e and NA64$\mu$ extremely complementary to each other and increases significantly the discovery potential of sub-GeV DM.