Pion photo- and electroproduction and the partially-conserved axial current

Abstract

The relevance of the axial current for pion production processes off the nucleon with real or virtual photons is revisited. Employing the hypothesis of a partially conserved axial current (PCAC), it is shown that, when all of the relevant contributions are taken into account, PCAC does not provide any additional constraint for threshold production processes that goes beyond the Goldberger-Treiman relation. In particular, it is shown that pion electroproduction processes at threshold cannot be used to extract any information regarding the weak axial form factor. The relationships found in previous investigations are seen to be an accident of the approximations usually made in this context.

4 pages, 3 figures; typos corrected; references updated; some rewording; conclusions unchanged

References in corpus (3)

• Gauge-invariant theory of pion photoproduction with dressed hadrons
• A measurement of the axial form factor of the nucleon by the p(e,e'pi+)n reaction at W=1125 MeV
• Preserving the gauge invariance of meson production currents in the presence of explicit final-state interactions

Cited by in corpus (6)

• Induced pseudoscalar coupling of the proton weak interaction
• Pion electroproduction, PCAC, chiral Ward identities, and the axial form factor revisited
• Chiral perturbation theory - Success and challenge
• Triality selection rules of Octonion and Quantum Mechanics
• On the pion electroproduction amplitude
• Comment about pion electro-production and the axial form factors