In-medium effective axial-vector coupling constant

The axial-vector coupling constant in nuclear medium is systematically studied using chiral perturbation theory. The first non-trivial corrections are estimated based on the independent particle approximation taking into account nuclear correlations in nuclear medium. The one-pion-exchange (OPE) two-body interactions turn out to enhance the coupling constant by δgAgA ⋍ (0.08−0.13) in normal nuclear matter. The four-nucleon contact interaction, if estimated by using the Δ-resonance contribution with the NN ↔ NΔ coupling fixed by the Landau-Migdal parameter g′NΔ ∼ 13, quenches the axial-vector coupling by δgAgA ∼ −0.28, thus resulting in the net quenching by δgAgA ⋍ (−0.15–−0.20). Conventional approaches are discussed in the light of our result.