Meson-exchange-currents contribution to axial charge transitions

We study the contribution of meson-exchange currents (MEC) to axial charge transitions in the framework of quantum hadrodynamics II. We extend a previous work which considered the contributions of one-body processes and vacuum polarization corrections. Calculations in mean-field theory (the Walecka model) and in the relativistic Hartree approximation are presented. In each of these cases we show results using pseudovector and pseudoscalar πN coupling. We find that the MEC contribution to the process is always sizable (much more so when using pseudoscalar coupling), transition dependent, and very sensitive to the coupling at the ρπ vertex