Abstract
The helicity dependence of the (gamma) over right arrow(d) over right arrow -> pi(0)d reaction is studied for incident photon lab-energies near the eta-threshold at backward center-of-mass pion angles. The influence of first-order rescattering with intermediate production of both pi- and eta-mesons on the doubly polarized differential and total cross sections for parallel and antiparallel helicity states is investigated. Then the contribution of (gamma) over right arrow(d) over right arrow -> pi(0)d to the deuteron spin asymmetry of the total cross section is calculated and its contribution to the Gerasimov-Drell-Hearn (GDH) integral for the deuteron is explicitly evaluated by integration up to a photon lab-energy of 900 MeV. Moreover, the double polarization E-asymmetry is predicted. Although the firstorder rescattering effect is found to be negligible in the doubly polarized total photo-absorption cross sections and the deuteron GDH integral, it reached on average about 40% in the doubly polarized differential cross sections and the helicity E-asymmetry at extreme backward direction in the eta-threshold region. We expect that these results may be useful to interpret the recent measurements from A2 and GDH@MAMI as well as CLAS@JLab Collaborations.