Description
Neutrinoless double beta decay (0νββ) is a rare nuclear transition. If it is observed, it would answer open questions about neutrino masse and nature. To convert the 0νββ half-life into the neutrino Majorana mass a precise knowledge of the Nuclear Matrix Elements (NMEs) is required, but their current evaluation is strongly model-dependent. The measurement of highly suppressed β-decay spectral shape is a benchmark to test and stress nuclear models, shading light on the g$_A$ quenching and possibly identifying its origin. A quenched value of g$_A$ produces a spectral distortion in highly-suppressed single β-decay spectra. These decays have a higher transferred momentum, more similar to 0νββ, and offer a unique probe of the g$_A$ quenching as they are not masked by any lower-order β-decays. In the list of interesting isotopes to be measured, Indium-115 is one of the most suitable due to the relatively high Q-value (497.954 keV) and half-life (4.41x10$^{14}$ yr). In the framework of the ACCESS (Array of Cryogenic Calorimeter to Evaluate Spectral Shapes) project, we evaluated the performances of two $^{115}$In-based crystals operated as cryogenic calorimeters. In this poster, we present the results obtained from the test of indium oxide and indium iodine crystals to study the spectral shape of $^{115}$In.
