The CROSS experiment: search for 0v2β decay with surface sensitive bolometers

Abstract

CROSS (Cryogenic Rare-event Observatory with Surface Sensitivity) is a project aiming to develop a new bolometric technology enabling an active background rejection in 0v2β search. The isotopes of interest are 100Mo and 130Te, and bolometers are based on Li2MoO4 and TeO2 crystals. The key feature of CROSS detectors is the possibility of pulseshape discrimination of near surface interactions. An ultrapure superconductive aluminum film, deposited on the crystal surface, is acting as a pulse-shape modifier for phonon sensors, providing separation of surface events from bulk ones. First prototypes were produced and successfully tested aboveground with the rejection of α surface radioactivity higher than 99.9%. A demonstrator with 32 0.28-kg Li2 100MoO4 crystals will be installed in a dedicated cryostat in the Canfranc underground laboratory (Spain) to confirm the reproducibility of surface sensitive bolometers. CROSS demonstrator can obtain sensitivities to the effective Majorana mass down to 70 meV in the most favorable conditions. The CROSS technology can be applied for future ton-scale experiments, reaching sensitivities to the effective Majorana mass down to 10 meV.