Theoretical study of 3He(μ-,νμ)3H capture

The 3He(μ-,νμ)3H weak capture is studied using correlated-hyperspherical-harmonics wave functions, obtained from realistic Hamiltonians consisting of the Argonne v14 or Argonne v18 two-nucleon, and Tucson-Melbourne or Urbana-IX three-nucleon interactions. The nuclear weak charge and current operators have vector and axial-vector components with one- and two-body contributions. The axial-vector current includes the nucleon and Δ induced pseudoscalar terms, with coupling constants gPS and gPS* derived from pion-pole dominance and partially conserved-axial-current hypothesis. The strength of the leading two-body operator is adjusted to reproduce the Gamow-Teller matrix element in tritium β decay. The calculated total capture rate is within ∼0.5% of the most recent measurement, 1496±4 sec-1. The predictions for the capture rate and angular correlation parameters Av, At, and AΔ are found to be only very weakly dependent on the model input Hamiltonian. The variation of the observables with gPS and gPS* and the theoretical uncertainties deriving from the model-dependent procedure used to constrain the axial current are investigated