R&D towards TES based Cherenkov light detection for CUPID

CUPID (CUORE Upgrade for Particle IDentification) is a next generation ton-scale bolometric detector to search for lepton number violating processes and probe 0νββ \nu\beta\beta in the full inverted neutrino mass hirarchy. To achieve this goal, backgrounds have to be at least two orders of magnitude lower with respect to CUORE, requiring the active rejection of the dominant background from alpha surface contaminations. Secondary bolometers in the form of thin wafers are an established method to detect Cherenkov or Scintillation light emitted from optically transparent or scintillating crystals and discriminate against these events. In Berkeley we study how to optimize the light output and signal for the Cherenkov light that can be expected from 0νββ \nu\beta\beta events in TeO2 _2 (~100eV). We report on this work which includes a study of the optical properties of TeO2 _2 and the development of very sensitive Ir-based bilayer TES sensors on Si wafers for optical photon detection.