Performance of the PADME calorimeter prototype at the DA$\hat{I}¦$NE BTF

Abstract

The PADME experiment at the DA$\hat{I}¦$NE Beam-Test Facility (BTF) aims at searching for invisible decays of the dark photon by measuring the final state missing mass in the process $e^{+}{e}^{-}\to {\hat{I}}^3+A^{\prime }$, with $A^{\prime }$ undetected. The measurement requires the determination of the 4-momentum of the recoil photon, performed using a homogeneous, highly segmented BGO crystals calorimeter. We report the results of the test of a 5$\times$5 crystals prototype performed with an electron beam at the BTF in July 2016.