# The NN final-state interaction in the helicity structure of $\vec d(\vec\gamma,\pi^-)pp$ reaction

Research paper by Eed M. Darwish

Indexed on: 10 Dec '04Published on: 10 Dec '04Published in: Nuclear Theory

#### Abstract

The influence of final-state $NN$-rescattering on the helicity structure of the $\vec\gamma\vec d\to\pi^-pp$ reaction in the energy range from $\pi$-threshold up to 550 MeV has been investigated. The differential polarized cross-section difference for the parallel and antiparallel helicity states is predicted and compared with recent experimental data. It is shown that the effect of $NN$-rescattering is much less important in the polarized differential cross-section difference than in the previously studied unpolarized differential cross section. Furthermore, the contribution of $\vec\gamma\vec d\to\pi^-pp$ to the spin asymmetry of the deuteron is explicitly evaluated over the region of the $\Delta$(1232)-resonance with inclusion of $NN$-rescattering. The effect of $NN$ final-state interaction is found to be much larger in the asymmetry than in the total cross section and leads to an appreciable reduction of the spin asymmetry in the $\Delta$-region.