Calculation of the neutrinoless ββ decay of 76Ge using a quark model with harmonic confinement

Abstract

The half-life of the neutrinoless double beta decay of 76Ge into the ground state of 76Se is calculated in a relativistic quark confinement model. The proton-neutron quasi-particle random-phase approximation is used to evaluate the s- and p-wave nuclear matrix elements contained in the decay amplitude. We avoid the closure approximation and calculate the effective vector and axial-vector coupling constants of the hadronic currents using our quark model. In our formulation the recoil matrix element arises from the quark recoil in the decaying neutrons. The recoil and the p-wave effect are discussed and compared with other calculations. From the experimental lower bound for the decay half-life an upper limit for the effective Majorana mass of the neutrino is deduced and the right-handed contribution to the charged weak current estimated.