Massive photon-like particles are predicted in many extensions of the Standard Model. They have interactions similar to the photon, are vector bosons, and can be produced together with photons.
The PADME experiment proposes a search for the dark photon (U) in the e+e-
-> gamma U process in a positron-on-target experiment, exploiting the positron beam of the DAFNE beam-test facility (BTF), produced by the LINAC, at the Laboratori Nazionali di Frascati (LNF), INFN.
Since the beam momentum is known at the level of 0.5%, by measuring
the momentum of the photon with a finely segmented calorimeter, it is
possible to close the kinematics of the events and look at the missing mass.
Such a model-independent search has never been performed to date, and all experimental exclusions rely on the hyphotesis of dominant decay to
In one year of running a sensitivity in the relative interaction strength down to 10^-6 is achievable, in the mass region from
2.5 MeV < MU< 22.5 MeV.
Upgrades of the LINAC, both increasing the maximum positron energy, and the pulse duration, would improve the sensitivity of the PADME experiment.
To exploit the production of dark photons in Bremsstrahlung processes and their subsequent decay into pairs of leptons U -> e+ e-, the experiment employs a magnetic spectrometer, which allows to probe and improve the current exclusions limits in visible decays. This can be achieved with two kind of setups: with a thinner target, by looking at e+ e- and mu+ mu- couples in the spectrometer, and by performing a real dump experiment, by looking at lepton pairs behind a thick target.
Different levels of mprovements of the current exclusions can be achieved, depending on the maximum integrated charge, in the range between 10^18 and 5 10^20 EOT.