$πNN$ and $πNΔ$ formfactors determined from a microscopic model for $πN$ scattering
Abstract
Description
We determine the $πNN$ and $πNΔ$ formfactors from the $P_{11}$ resp. $P_{33}$ partial wave of $πN$ scattering by dressing corresponding bare vertices with the help of $πN$ non--pole contributions. The underlying model is based on meson exchange, and involves nucleon and delta--isobar pole and crossed--pole terms together with correlated $ππ$--exchange in the $J^P=0^+$ ($σ$) and $1^-$ ($ρ$) channel. The results are very similar for $πNN$ and $πNΔ$ and can be roughly parametrized by a monopole with cutoff mass $>$ 500 MeV, with some variation due to model dependencies. Thus the formfactors are much less soft than derived before for the $πNN$ case by Saito and Afnan using the same procedure but different $πN$ interaction models.
7 pages, 4 postscript figures
7 pages, 4 postscript figures