HARD PIONS AND AXIAL MESON EXCHANGE CURRENT EFFECTS IN NEGATIVE MUON-CAPTURE IN DEUTERIUM

The contribution of the axial meson exchange current effects to the doublet transition rate in the reaction μ- +d → 2n+ νμ is calculated by using the minimal, chiral and approximately gauge invariant Lagrangian model for the A1ρπ system. The contribution from the ρ-π weak decay process current usually considered is found to be nearly cancelled by that from the A1 pole graph which is prescribed by the underlying invariance principles. Correct treatment of the N* propagator in the N* excitation current of the pion range leads to ≈ 30 % suppression of the N* effect. © 1979.