Search for dark photons using a multilayer dielectric haloscope equipped with a single-photon avalanche diode

Abstract

We report on the results of the search for dark photons with mass around 1.5 eV/c 2 using a multilayer dielectric haloscope equipped with an affordable and commercially available photosensor. The multilayer stack, which enables the conversion of dark photons (DP) to Standard Model photons, is made of 23 bilayers of alternating SiO2 and Si3N4 thin films with linearly increasing thicknesses through the stack (a configuration known as a "chirped stack"). The thicknesses have been chosen according to an optimisation algorithm in order to maximise the DP-photon conversion in the energy region where the photosensor sensitivity peaks. This prototype experiment, baptised MuDHI (Multilayer Dielectric Haloscope Investigation