%0 Report
%A Körfgen, Bernd
%T Pion- und Photoabsorption an Kernen im Delta-Resonanzbereich
%V 2540
%N Juel-2540
%C Jülich
%I Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
%M FZJ-2018-03649
%M Juel-2540
%B Berichte des Forschungszentrums Jülich
%P 91 p.
%D 1991
%X In charge-exchange reactions and in $\pi$-absorption at intermediate energies the $\Delta$ peak position in nuclei is shifted downwards in energy compared to the $\Delta$-excitation of the nucleon. For electromagnetic probes the experimental data do not show such a shift. We describe the excitation of the $\Delta$ in nuclei consistently for all these different probes using the isobar-hole-model ($\Delta$N$^{-1}$-model). The shift of the $\Delta$ peak position in chargeexchange reactions and in $\pi$-absorption is due to an attractive $\Delta$N$^{-1}$-residual interaction in the spin-longitudinal ($\overrightarrow{\sigma} \cdot \overrightarrow{q}$) channel. A $\Delta$N$^{-1}$-residual interaction consisting of the $\pi$-exchange potential alone is too attractive in the spin-longitudinal channel and shifts the $\Delta$ peak position for $\pi$-absorption to too low energies. In order to reproduce the $\Delta$ peak position we have to include short range correlations in the $\Delta$N$^{-1}$-residual interaction. This is done either by adding a $\delta$-force, parametrized through the Landau-Migdal-parameter g$^{'}_{\Delta \Delta}$, to the $\pi$-exchange potential, or by multiplying the $\pi$-exchange potential with a correlation-function. This leads to a repulsive $\Delta$N$^{-1}$-residual interaction in the spin-transverse ($\overrightarrow{\sigma}$ x $\overrightarrow{q}$) channel, which shifts the $\Delta$ peak position in the calculations for photo-absorption to higher energies compared to the photo-absorption on the nucleon.
%F PUB:(DE-HGF)3 ; PUB:(DE-HGF)29
%9 BookReport
%U https://juser.fz-juelich.de/record/848413