Effects of the final-state interaction in ($\gamma$,pn) and ($\gamma$,pp) processes

Abstract

A model is presented to describe electromagnetically induced two-nucleon emission processes in a shell-model picture. Distortions in the outgoing nucleon waves are accounted for by performing a partial-wave expansion in a real mean-field potential. The antisymmetry condition for the A-body wavefunctions is shown to be naturally preserved. The model is used to calculate ($\gamma$,pn) and ($\gamma$,pp) cross sections off the target nuclei ${}^{16}$O and ${}^{12}$C for photon energies ranging from 50 MeV up to the $△$(1232) isobar threshold. Effects due to the pionic currents and intermediate $△$ creation are implemented. The impact of the distortions due to the interaction of the outgoing nucleon waves with the (A-2) core is examined. Hadronic form factors are introduced to regularize the $\pi$NN vertices and the sensitivity of the cross section to the pion cut-off mass is examined. The relative contribution of the ($\gamma$,pp) and the ($\gamma$,pn) channel to the total photoabsorption strength is discussed. Further, the photon energy dependence of the ($\gamma$,pp)/($\gamma$,pn) ratio is investigated.

30 pages, 11 figures (available from the authors upon request), INW0701

References in corpus (1)

• Absorption mechanisms in photon induced two-body knockout

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