Physicists in Italy are about to start up a new experiment designed to hunt for hypothetical particles such as the “dark photon” and carriers of a possible fifth force of nature. The Positron Annihilation into Dark Matter Experiment (PADME), located at the National Institute of Nuclear Physics (INFN) laboratories in Frascati outside Rome, will blast a thin diamond target with energetic positrons and record the mass of any exotic new particles produced in the collisions.