Abstract
The requirement of gauge invariance is applied to the matrix element for pion photoproduction near threshold for spin → and → transitions and leads to relations between and , and to partially conserved axial-vector current relations. These relations lead to theoretical predictions for cross sections consistent with experiment within the level of approximations made. Straightforward analytic continuation of the axial-vector form factor to the timelike region is also examined.
NUCLEAR REACTIONS Gauge invariance, PCAC, weak nuclear form factors for (,) and (,).
- Received 14 September 1981
DOI:https://doi.org/10.1103/PhysRevC.25.1986
©1982 American Physical Society