Orateur
Description
Neutrinoless double beta decay is a hypothetical process of great interest for neutrino physics. If observed, it would confirm the Majorana nature of neutrinos. Currently, technologies used for ton-scale experiments will reach sensitivities of O(10) meV to effective Majorana mass (mbb). However, if we need further investigation with higher sensitivities, innovative detection techniques have to be developed. This is the focus of BINGO (Bi-Isotope 0νββ Next Generation Observatory) and TINY (Two Isotopes for Neutrinoless double beta decaY search) projects: advance the neutrinoless double beta decay searches beyond current reach with bolometric detectors.
BINGO focuses on background reduction and strategically combines two isotopes, 100Mo and 130Te, embedded in Li2MoO4 and TeO2 crystals. Key features of the BINGO project include a compact detectors’ assembly to minimise passive materials, enhanced light detectors and a BGO-scintillator-based cryogenic veto. Thanks to the higher Q-value of 100Mo, LMOs are less affected by natural β/γ backgrounds. Additionally, NTL-assisted light detectors will enable efficient α-background rejection in TeO2 crystals and pile-up rejection in LMOs. A dedicated cryogenic infrastructure has been installed and validated at the Modane Underground Laboratory (LSM), providing the necessary environment for low-background operations. Data-taking with prototype detectors is ongoing to validate the technological solutions and optimise the final design. A first physics run with MINI-BINGO is foreseen for the beginning of autumn. The TINY project aims to develop bolometric detectors incorporating 96Zr and 150Nd isotopes, which have the highest Qββ values among candidate nuclei, thus positioning the region of interest above most natural gamma and beta backgrounds. Additionally, the large phase-space factor enhances sensitivity to the effective Majorana neutrino mass. A 20 g Cs2ZrCl6 (CZC) crystal was measured for the first time as a scintillating bolometer, with simultaneous heat and light readout, using NTDs (Neutron transmutation doped) thermistors. The results demonstrate a promising performance in terms of sensitivity and energy resolution and the dual readout provides efficient discrimination between β/γ and α events, confirming the feasibility of building a Zr-based 0νββ bolometric experiment. A small-scale demonstrator is planned at the end of the project, with the aim to get precision measurement of 2νββ spectra of the isotopes under investigation and to achieve new limits for their 0νββ decays.