Is the Decay of the Higgs Boson to a Photon and a Dark Photon Currently Observable at the LHC?

Hugues Beauchesne and Cheng-Wei Chiang
Phys. Rev. Lett. 130, 141801
DOI: https://doi.org/10.1103/PhysRevLett.130.141801

The potential decay of the Higgs boson to a photon and a massless dark photon has been the subject of multiple dedicated searches at the LHC. For this decay to be realistically observable, new mediators that communicate between the standard model particles and the dark photon must exist. In this work, we studied constraints on these mediators coming from the Higgs signal strengths, oblique parameters, electric dipole moment of the electron, and unitarity. We found that this branching ratio is far more constrained than previously expected, putting into question the possibility of ever observing this decay at the LHC.