Search for the dark photon in π0 decays

Abstract

A sample of 1.69 × 107 fully reconstructed π0 → γe+e− in the kinematic range mee > 10MeV/c2 with a negligible background contamination collected by the NA48/2 experiment at CERN in 2003-04 is analysed to search for the dark photon (A′) via the decay chain π;0 → γA′, A′ → e+e. No signal is observed, and preliminary exclusion limits on space of dark photon mass mA′ and mixing parameter ϵ2 are reported.