Arbitrary mass Majorana neutrinos in neutrinoless double beta decay

We revisit the mechanism of neutrinoless double beta (0 nu beta beta) decay mediated by the exchange with the heavy Majorana neutrino N of arbitrary mass m(N), slightly mixed similar to U-eN with the electron neutrino nu(e). By assuming the dominance of this mechanism, we update the well-known 0 nu beta beta-decay exclusion plot in the m(N) - U-eN plane taking into account recent progress in the calculation of nuclear matrix elements within quasiparticle random phase approximation and improved experimental bounds on the 0 nu beta beta-decay half-life of Ge-76 and Xe-136. We also consider the known formula approximating the m(N) dependence of the 0 nu beta beta-decay nuclear matrix element in a simple explicit form. We analyze its accuracy and specify the corresponding parameters, allowing one to easily calculate the 0 nu beta beta-decay half-life for arbitrary m(N) for all the experimentally interesting isotopes without resorting to real nuclear structure calculations.