The NN final-state interaction in the helicity structure of reaction

Abstract

The influence of final-state N N -rescattering on the helicity structure of the γ d → π − pp reaction in the energy range from π-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 N N -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 γ d → π − pp to the spin asymmetry of the deuteron is explicitly evaluated over the region of the ∆(1232)resonance with inclusion of N N -rescattering. The effect of N N 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 ∆-region.

Incoherent pion photoproduction on the deuteron with polarization observables. I. Formal expressions

“…Moreover, this statement is in contradiction to Ref. [10], where a nonvanishing differential spin asymmetry for circularly polarized photons is reported, because this asymmetry is proportional to the beam-target asymmetry T c 10 for circularly polarized photons and a vector polarized deuteron, which means that the latter does not vanish. Thus, it is obvious that the importance of polarization effects requires a more careful and thorough treatment as done in Refs.…”

“…It appears that this fact was not taken into account so that the results in Refs. [9,10] for them cannot be trusted. But also the results for circularly polarized photons are incorrect, namely the claim in Ref.…”

“…Thus, it is obvious that the importance of polarization effects requires a more careful and thorough treatment as done in Refs. [8][9][10][11][12].…”

Helicity dependence and contribution to the Gerasimov-Drell-Hearn sum rule of theγ→d→→πNNreaction channels

“…The helicity dependence of the d( γ , π − )pp reaction channel was investigated in Ref. [11] with just the inclusion of NN rescattering in the final state. In that work, the differential polarized cross-section difference for parallel and antiparallel helicity states was predicted and the contribution of the d( γ , π − )pp channel to the deuteron spin asymmetry was evaluated.…”

“…It was found that the effects of final state interactions (FSI) are larger in the asymmetry than in the unpolarized cross sections, which leads to a sizeable reduction of the deuteron spin asymmetry in the position of the peak. Both approaches [10,11] were restricted to the (1232)-resonance region in view of a relatively simple elementary pion photoproduction operator based on an effective Lagrangian approach from Ref. [13] that included only Born terms and the (1232) resonance.…”