Selected nucleon form factors and a composite scalar diquark

Bloch, J. C. R.; Roberts, C. D.; Schmidt, S. M.

Selected nucleon form factors and a composite scalar diquark

Authors

Bloch, J. C. R.

Roberts, C. D.

Schmidt, S. M.

Description

A covariant, composite scalar diquark, Fadde'ev amplitude model for the nucleon is used to calculate pseudoscalar, isoscalar- and isovector-vector, axial-vector and scalar nucleon form factors. The last yields the nucleon sigma-term and on-shell sigma-nucleon coupling. The calculated form factors are soft, and the couplings are generally in good agreement with experiment and other determinations. Elements in the dressed-quark-axial-vector vertex that are not constrained by the Ward-Takahashi identity contribute ~20% to the magnitude of g_A. The calculation of the nucleon sigma-term elucidates the only unambiguous means of extrapolating meson-nucleon couplings off the meson mass-shell.
12 pages, REVTEX, 5 figures, epsfig