Attempts to reconcile a 17-keV neutrino with constraints from astrophysics and double beta decay have led to model Majorana neutrino mass matrices with vanishing (or nearly vanishing) electron-electron components. A simple parametrization is presented of the higher-order mass effects on the intermediate-state propagator through which 0ν ββ decay can still occur. For light-mass eigenstates, the 0ν and 2ν rates are proportional, with the ratio depending on a weighted sum over mass eigenstates 〈${\mathit{m}}_{\nu }^3$${\mathrm{〉}}_{\mathit{L}\mathit{L}}^{\mathrm{Maj}}$. Thus, model 0ν ββ decay rates can be predicted with confidence.

• Received 18 July 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.2431