PADME: searching for dark mediator at the Frascati BTF

Massive photon-like particles are predicted in many extensions of the Standard Model with a hidden sector accounting for dark matter candidates. They have interactions similar to the photon, are vector bosons, and can be produced together with photons. Most of the present experimental constraints on the dark photon (A) rely on the hypothesis of dominant decays to lepton pairs. The PADME experiment aims at searching for the e+e- → γA process in a positron-on-target experiment, assuming a decay of the A into invisible particles of the hidden sector. The positron beam of the DAΦNE Beam-Test Facility (BTF), produced by the LINAC at the Laboratori Nazionali di Frascati of INFN, will be used. The core of the experimental apparatus is a fine-grained, high-resolution calorimeter. It will measure with high precision the momentum of the photon in events with no other activity in the detector, thus allowing to measure the A mass as the missing mass in the final state. In about one year data taking, a sensitivity on the interaction strength (ϵ2 parameter) down to 10- is achievable, in the mass region from 1 MeV < MA < 23.7 MeV, running with 6000 positrons in 40 ns long bunches at 550 MeV beam energy. The experiment, now in the construction phase, is planned to run in 2018. The status of the PADME detector and the physics potential of PADME is reviewed.