Dark Photons and Hidden Sector Models

Dark Photons and Hidden Sector Models propose a parallel 'dark sector' with its own forces, mediated by a dark photon coupling feebly to ordinary matter via a kinetic mixing parameter below 10⁻⁶. Jefferson Lab and CERN's NA62 have searched for dark photons in the 10-100 MeV mass range with no evidence. This makes the hidden sector 40% less constrained than SIDM, raising the question of whether it is hiding or nonexistent. A concrete upper limit on the mixing parameter is 5 × 10⁻⁷ from XENON1T data.