Neutrino Masses and Right-Handed Weak Currents Studied by Neutrino-Less ββ-Decay Detectors

Detecting neutrino-less double beta (0νββ) decay with high-sensitivity 0νββ detectors is of current interest for studying the Majorana neutrino’s nature, the neutrino mass (ν-mass), right-handed weak currents (RHCs), and others beyond the Standard Model. Many experimental groups have studied 0νββ decay with ν-mass sensitivities on the order of 100 meV and RHC sensitivities on the order of 10 −9–10 −6, but no clear 0νββ signals have been observed so far in these ν-mass and RHC regions. Thus, several experimental groups are developing higher-sensitivity detectors to explore a smaller ν-mass region around 15–50 meV, which corresponds to the inverted hierarchy ν-mass, and smaller RHC regions on the order of 10 −10–10 −7 in the near future. Nuclear matrix elements (NMEs) for ν-mass and RHC processes are crucial for extracting the ν-mass and RHCs of particle physics interest from 0νββ experiments. This report briefly reviews detector sensitivities and upper limits on the ν-mass and right-handed currents for several current 0νββ detectors and the ν-mass and RHC sensitivities expected for some near-future ones.