2024

Pagnanini, L.; Benato, G.; Carniti, P.; Celi, E.; Chiesa, D.; Corbett, J.; Dafinei, I.; Di Domizio, S.; Di Stefano, P.; Ghislandi, S.; Gotti, C.; Helis, D. L.; Knobel, R.; Kostensalo, Joel; Kotila, J.; Nagorny, S.; Pessina, G.; Pirro, S.; Pozzi, S.; Puiu, A.; Quitadamo, S.; Sisti, M.; Suhonen, J.; Kuznetsov, S.

Current bounds on neutrino Majorana mass are affected by significant uncertainties in the nuclear calculations for neutrinoless double-beta decay. A key issue for a data-driven improvement of the nuclear theory is the actual value of the axial coupling constant gA, which can be investigated through forbidden β-decays. We present the first measurement of 4th-forbidden β-decay of 115In with a cryogenic calorimeter based on Indium Iodide. Exploiting the enhanced spectral shape method for the first time to this isotope, our study accurately determines simultaneously spectral shape, gA, and half-life. The Interacting Shell Model, which best fits our data, indicates a half-life for this decay at T1/2=(5.26±0.06)×1014,yr.