Parity-violating asymmetry in the He-3(n-polarized, p)H-3 reaction

The longitudinal asymmetry induced by parity-violating (PV) components in the nucleon-nucleon potential is studied in the charge-exchange reaction He-3(n-polarized, p)H-3 at vanishing incident neutron energies. An expression for the PV observable is derived in terms of T-matrix elements for transitions from the L-2S+1(J) = S-1(0) and S-3(1) states in the incoming n-He-3 channel to states with J = 0 and 1 in the outgoing p-H-3 channel. The T-matrix elements involving PV transitions are obtained in first-order perturbation theory in the hadronic weak-interaction potential, while those connecting states of the same parity are derived from solutions of the strong-interaction Hamiltonian with the hyperspherical-harmonics method. The coupled-channel nature of the scattering problem is fully accounted for. Results are obtained corresponding to realistic or chiral two-and three-nucleon strong-interaction potentials in combination with either the DDH or pionless EFT model for the weak-interaction potential. The asymmetries, predicted with PV pion and vector-meson coupling constants corresponding (essentially) to the DDH "best values" set, range from -9.44 to -2.48 in units of 10(-8), depending on the input strong-interaction Hamiltonian. This large model dependence is a consequence of cancellations between long-range (pion) and short-range (vector-meson) contributions and is of course sensitive to the assumed values for the PV coupling constants.