Time-reversal invariance in the β-decays of A = 8 nuclei

Abstract We examine time-reversal invariance in the β-decays of 8 B(2 + ) and 8 Li(2 + ) to 8 Be(2 + ) in detail, with particular attention to final-state interactions of the two α-particles from the decay of 8 Be, and of the electron (positron) with the daughter nucleus. An R -matrix formulation is used, with the initial state described by a shell model. The R -matrix parameters are obtained by fitting the αα-scattering phase shifts and allowed β-decay rates. Because the nuclear finalstate interaction effects on the time-reversal test come from second forbidden β-decays, they are small and can be minimized by a suitable choice of kinematic conditions. The e ± -nucleus Coulomb-interaction-induced T -violation effects depend on the first forbidden operators.