Is the decay of the Higgs boson to a photon and a dark photon currently observable at the LHC?

TL;DR

This paper evaluates the potential observability of Higgs decays to a photon and a dark photon at the LHC, concluding current bounds make detection unlikely without new physics.

Contribution

It provides new bounds on mediators between the Standard Model and dark photons based on multiple experimental constraints, impacting future search strategies.

Findings

Higgs to photon and dark photon decay is highly suppressed.

Current collider sensitivities are insufficient to detect this decay.

Constraints from Higgs signals, oblique parameters, and electric dipole moments are significant.

Abstract

Many attempts have been made to observe the decay of the Higgs boson to a photon and an invisible massless dark photon. For this decay to be potentially observable at the LHC, new mediators that communicate between the Standard Model and the dark photon must exist. In this Letter, we study bounds on such mediators coming from the Higgs signal strengths, oblique parameters, electric dipole moment of the electron and unitarity. We find that the branching ratio of the Higgs boson to a photon and a dark photon is constrained to be far smaller than the sensitivity of current collider searches, thus calling for a reconsideration of current experimental efforts.