Relaxing constraints on a broad dark photon

Abstract

We revisit the exclusion constraints on the parameters of a narrow dark photon set by direct experimental searches. We investigate how a dark photon with a larger decay width impacts these limits, in particular, in the case where the dark photon also decays into light dark matter. As an example, taking the upper limits on the mixing parameter, $\epsilon$, reported by the CMS collaboration, we find that they could be significantly relaxed. Indeed, even a very modest coupling of the dark photon to dark matter can lead to an increase in the bound on the mixing parameter by an order of magnitude.