What are dark photons and could they explain dark matter?

The answer

Dark photons are hypothetical particles that would mediate a force in a hidden 'dark sector,' analogous to how ordinary photons carry the electromagnetic force. If they exist, dark photons could interact weakly with normal matter through kinetic mixing - providing a portal between visible and dark matter. Experiments searching for dark photons include the Heavy Photon Search at Jefferson Lab, the NA64 experiment at CERN, and the DarkLight experiment at MIT. In 2023, the NA64 collaboration set new constraints excluding dark photons in the 1-200 MeV mass range with mixing parameters above 10⁻⁵. Dark photons could explain the muon g-2 anomaly and certain astrophysical observations. If discovered, they would confirm the existence of an entirely new force of nature beyond the four currently known.