Search for Dark Sector Physics at the NA64 experiment in the context of the Physics Beyond Colliders Project

Understand

The NA64 electron beam program comprises of a high sensitivity search for visible and invisible decays of the hypothetical dark photon, $A'$, with a goal to either observe the sub-GeV Dark Matter mediator or exclude most of the model parameter space.

• The visible channel search also includes clarification of the origin of the $^8$Be anomaly observed by the Atomki experiment.
• The NA64 collaboration further aims to expand its searches with a proposal to use the muon beam at the CERN M2 beam line which will focus on the unique possibility to search for a new scalar or vector states weakly coupled predominantly to muons, e.g.
• a new Z$_\mu$ gauge boson of L$_\mu$ - L$_\tau$ symmetry, which might explain the long standing muon (g-2)$_\mu$ anomaly.