Barbara Mele (INFN, Roma)
Massless Dark Photons at Colliders
Recent models, possibly explaining the fermion-mass hierarchy, predict the existence of a massless dark photon. Its interactions are restricted to a hidden sector made up of massive dark fermions (which are promising dark-matter candidates), and heavier scalar messengers connecting the SM with the dark fields. Thanks to the nondecoupling properties of the Higgs boson, exotic Higgs interactions with the invisible dark photon can show up at present and future colliders with measurable rates. Predictions for new Higgs signatures and corresponding rates are presented. A new class of FCNC’s mediating SM fermion decays into massless dark photons are also discussed.