Model for the Cherenkov light emission of TeO2 cryogenic calorimeters

Abstract

The most sensitive process able to probe the Majorana nature of neutrinos and discover Lepton Number Violation is the neutrino-less double beta decay. Thanks to the excellent energy resolution, efficiency and intrinsic radio-purity, cryogenic calorimeters are primed for the search for this process. A novel approach able to improve the sensitivity of the current experiments is the rejection of α interactions, that represents the dominant background source. In TeO2 calorimeters, α particles can be tagged as, in contrast to electrons, they do not emit Cherenkov light. Nevertheless, the very low amount of detected Cherenkov light undermines the complete rejection of α background.In this paper we compare the results obtained in previous measurements of the TeO2 light yield with a detailed Monte Carlo simulation able to reproduce the number of Cherenkov photons produced in β/γ interactions within the calorimeter and their propagation in the experimental set-up. We demonstrate that the light yield detectable from a 5 × 5 × 5 cm3 TeO2 bolometer can be increased by up to 60% by increasing the surface roughness of the crystal and improving the light detector design.Moreover, we study the possibility to disentangle α, β and γ interactions, which represent the ultimate background source. Unfortunately γ rejection is not feasible but α rejection can be achieved exploiting high sensitivity light detectors.