Complete spin structure of the pion-nucleon-loop delta self-energy

Abstract

The complete spin structure of the pion-nucleon-loop contribution to the delta self-energy and dressed propagator is calculated in vacuum, with the most general form of the pion-nucleon-delta vertex. The imaginary parts of the ten Lorentz-scalar coefficients are calculated in closed form, while the real parts are obtained numerically from a dispersion relation. The effect of the pion-nucleon-delta coupling constants and form-factor on the pion-nucleon phase-shift in the spin-3/2 isospin-3/2 channel is studied.

Comments: 8 pages, LaTex (uses Revtex and epsf), 2 figures (included), errors in some expressions (including typos) corrected, numerical results affected very little, conclusions unchanged