Background suppression in massive TeO${}_2$ bolometers with Neganov-Luke amplified light detectors

Bolometric detectors are excellent devices for the investigation of neutrinoless double-beta decay (0$\nu \beta \beta$). The observation of such decay would demonstrate the violation of lepton number, and at the same time it would necessarily imply that neutrinos have a Majorana character. The sensitivity of cryogenic detectors based on TeO${}_2$ is strongly limited by the alpha background in the region of interest for the 0$\nu \beta \beta$ of ${}^{130}$Te. It has been demonstrated that particle discrimination in TeO${}_2$ bolometers is possible measuring the Cherenkov light produced by particle interactions. However an event-by-event discrimination with NTD-based light detectors has to be demonstrated. We will discuss the performance of a highly-sensitive light detector exploiting the Neganov-Luke effect for signal amplification. The detector, being operated with NTD-thermistor and coupled to a 750 g TeO${}_2$ crystal, shows the ability for an event-by-event identification of electron/gamma and alpha particles. The extremely low detector baseline noise, RMS 19 eV, demonstrates the possibility to enhance the sensitivity of TeO${}_2$-based 0$\nu \beta \beta$ experiment to an unprecedented level.