Weak Magnetism in Two Neutrino Double Beta Decay

Abstract

We have extended the formalism for the two-neutrino double beta decay by including the weak-agnetism term, as well as other second-forbidden corrections. The weak magnetism diminishes the calculated half-lives in ∼ 10%, independently of the nuclear structure. Numerical computations were performed within the pn-QRPA, for ⁷⁶Ge, ⁸²Se, ¹⁰⁰Mo, ¹²⁸T e and ¹³⁰T e nuclei. No one of the second-forbidden corrections modifies significantly the spectrum shapes. The total reduction in the calculated half lives varies from 6% up to 32%, and strongly depend on the nuclear interaction in the particle-particle S = 1, T = 0 channel. We conclude that the higher order effects in the weak Hamiltonian would hardly be observed in the two-neutrino double beta experiments.