Combined constraints on dark photons and discovery prospects at the LHC and the Forward Physics Facility

TL;DR

This paper investigates constraints on dark photons from collider and detection experiments, exploring discovery prospects at the HL-LHC and future forward detectors, and analyzing the parameter space for dark matter models involving hidden sectors.

Contribution

It provides a comprehensive analysis of dark photon constraints across a wide mass range and assesses future discovery potential at collider and forward physics experiments.

Findings

Dark photon parameter space is highly constrained when decaying to dark matter.

Limits are weaker for dark photons without dark decays.

A self-thermalized dark sector is favored to satisfy relic density.

Abstract

Hidden sectors are ubiquitous in supergravity theories, in strings and in branes. Well motivated models such as the Stueckelberg hidden sector model could provide a candidate for dark matter. In such models, the hidden sector communicates with the visible sector via the exchange of a dark photon (dark $Z'$) while dark matter is constituted of Dirac fermions in the hidden sector. Using data from collider searches and precision measurements of SM processes as well as the most recent limits from dark matter direct and indirect detection experiments, we perform a comprehensive scan over a wide range of the $Z'$ mass and set exclusion bounds on the parameter space from sub-GeV to several TeV. We then discuss the discovery potential of an $\mathcal{O}$(TeV) scale $Z'$ at HL-LHC and the ability of future forward detectors to probe very weakly interacting sub-GeV $Z'$ bosons. Our analysis shows that the parameter space in which a $Z'$ can decay to hidden sector dark matter is severely constrained whereas limits become much weaker for a $Z'$ with no dark decays. The analysis also favors a self-thermalized dark sector which is necessary to satisfy the dark matter relic density.