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@TECHREPORT{Krfgen:848413,
      author       = {Körfgen, Bernd},
      title        = {{P}ion- und {P}hotoabsorption an {K}ernen im
                      {D}elta-{R}esonanzbereich},
      volume       = {2540},
      number       = {Juel-2540},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2018-03649, Juel-2540},
      series       = {Berichte des Forschungszentrums Jülich},
      pages        = {91 p.},
      year         = {1991},
      abstract     = {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.},
      cin          = {PRE-2000},
      cid          = {I:(DE-Juel1)PRE2000-20140101},
      pnm          = {899 - ohne Topic (POF3-899)},
      pid          = {G:(DE-HGF)POF3-899},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)29},
      url          = {https://juser.fz-juelich.de/record/848413},
}