HYPOTHESIS OF PARTIALLY CONSERVED AXIAL-VECTOR CURRENT AND MESON-EXCHANGE EFFECTS IN P+P-]D+PI+ AND H-3-]HE-3+E-+VE

The hypothesis of partially conserved axial-vector current (PCAC) is applied to relate the threshold production amplitude for the process α→β+π+ to the meson-exchange contributions in α→β+e-+ν̄e, where α and β are nuclear states. The latter contributions are calculated by assuming that the two-nucleon β-decay process Ni+Nj→Ni′+Nj′+e-+ν̄e is dominated by the one-pion-exchange contribution. Particular attention is given to the radial dependence of the effective two-body operator which is used to describe both p+p→d+π+ and the meson-exchange effects in H3→He3+e-+ν̄e. It is shown that terms as singular as x-2e-x and x-3e-x can arise naturally in a dynamical (as opposed to a phenomenological) treatment of meson-exchange effects, and that these terms contribute significantly to p+p→d+π+ but not at all to H3→He3+e-+ν̄e. Some discussion of the present experimental status of these two processes is also given. © 1969 The American Physical Society.