Tentative sensitivity of future 0νββ-decay experiments to neutrino masses and Majorana CP phases

In the near future, the neutrinoless double-beta (0 nu beta beta) decay experiments will hopefully reach the sensitivity of a few meV to the effective neutrino mass |m(beta beta)|. In this paper, we tentatively examine the sensitivity of future 0 nu beta beta -decay experiments to neutrino masses and Majorana CP phases by following the Bayesian statistical approach. Provided experimental setups corresponding to the experimental sensitivity of |m(beta beta)| similar or equal to 1 meV, the null observation of 0 nu beta beta decays in the case of normal neutrino mass ordering leads to a very competitive bound on the lightest neutrino mass m(1). Namely, the 95% credible interval in the Bayesian approach turns out to be 1.6 meV less than or similar to m(1) less than or similar to 7.3 meV or 0.3 meV less than or similar to m(1) less than or similar to 5.6 meV when the uniform prior on m(1)/eV or on log(10)(m(1)/eV) is adopted. Moreover, one of two Majorana CP phases is strictly constrained, i.e., 140 degrees less than or similar to rho less than or similar to 220 degrees for both scenarios of prior distributions of m(1). In contrast, if a relatively worse experimental sensitivity of |m(beta beta)| similar or equal to 10 meV is assumed, the constraint on the lightest neutrino mass becomes accordingly 0.6 meV less than or similar to m(1) less than or similar to 26 meV or 0 less than or similar to m(1) less than or similar to 6.1 meV, while two Majorana CP phases will be essentially unconstrained. In the same statistical framework, the prospects for the determination of neutrino mass ordering and the discrimination between Majorana and Dirac nature of massive neutrinos in the 0 nu beta beta -decay experiments are also discussed. Given the experimental sensitivity of |m(beta beta)| similar or equal to 10 meV (or 1 meV), the strength of evidence to exclude the Majorana nature under the null observation of 0 nu beta beta decays is found to be inconclusive (or strong), no matter which of two priors on m(1) is taken