Probing sub-eV Dark Matter decays with PTOLEMY

Abstract When the Dark Matter mass is below eV-scale, its cosmological occupation number exceeds ones of photons from cosmic microwave background as well relic neutrinos. If such decays to pairs neutrinos, it implies that experiments seek detection neutrino may be sensitive this additional form “dark radiation”. Here we study prospects for taking into account various options forecasted performance future PTOLEMY experiment. From a detailed profile likelihood analysis find with lifetime large 10 4 Gyr or sub-% fraction decaying today can discovered. The are facilitated by distinct spectral event shape introduced galactic and dark radiation fluxes. In process also clarify importance Pauli-blocking in decay. scenarios presented work considered early physics targets development these instruments relaxed demands on energy resolution.