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-magnetism term, as well as other second-forbidden corrections. The weak magnetism diminishes the calculated half-lives in $\sim 10$, independently of the nuclear structure. Numerical computations were performed within the pn-QRPA, for ${}^{76}Ge$, ${}^{82}Se$, ${}^{100}Mo$, ${}^{128}Te$ and ${}^{130}Te$ 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.

Comments: 8 pages, latex, 1ps figure, to appear in Phys. Lett. B