NN Final-State Interaction in the Helicity Dependence of Inclusive π−\pi^- Photoproduction from the Deuteron

The helicity dependence of the inclusive $\pi^-$ photoproduction reaction from the deuteron in the $\Delta$(1232)-resonance region is investigated with inclusion of final-state nucleon-nucleon rescattering ($NN$-FSI). For the elementary $\pi$-production operator an effective Lagrangian model which includes the standard pseudovector Born terms and a contribution from the $\Delta$-resonance is used. The half-off-shell $NN$-scattering matrix is obtained from a separable representation of a realistic $NN$-interaction. The differential polarized cross-section difference for parallel and antiparallel helicity states is predicted and compared with experiment. We find that the effect of $NN$-FSI is much less important in the helicity difference than in the previously studied unpolarized differential cross section. Furthermore, the contribution of $\vec d(\vec\gamma,\pi^-)pp$ to the deuteron spin asymmetry is explicitly evaluated with inclusion of $NN$-FSI. It has been found that the effect of $NN$-FSI is much larger in the asymmetry than in the total cross section, and this leads to an appreciable reduction of the spin asymmetry in the $\Delta$-region. Inclusion of such effect also leads to improved and quite satisfactory agreement with existing experimental data.Comment: 13 pages, 6 eps figures, published in Prog. Theor. Phys. 113 (2005) 169-18

Influence of NNNN-rescattering effect on the photon asymmetry of d(γ⃗,π−)ppd(\vec{\gamma},\pi^-)pp reaction

The influence of final-state $NN$-rescattering on the beam asymmetry $\Sigma$ for linearly polarized photons in $\pi^-$ photoproduction on the deuteron in the energy range from $\pi$-threshold through the $\Delta$(1232)-resonance has been investigated. Numerical results for this spin observable are predicted and compared with recent experimental data from the LEGS Spin collaboration. Final-state $NN$-rescattering is found to be quite important and leads to a better agreement with existing experimental data. Furthermore, the differences with other theoretical models have been discussed.Comment: 10 pages, 5 ps figures, accepted for publication in Physics Letters B, 200

Spin observables for pion photoproduction on the deuteron in the Δ\Delta(1232)-resonance region

Spin observables for the three charge states of the pion for the pion photoproduction reaction on the deuteron, $\gamma d\to\pi NN$, with polarized photon beam and/or oriented deuteron target are predicted. For the beam-target double-spin asymmetries, it is found that only the longitudinal asymmetries $T_{20}^{\ell}$ and $T_{2\pm 2}^{\ell}$ do not vanish, whereas all the circular and the other longitudinal asymmetries do vanish. The sensitivity of spin observables to the model deuteron wave function is investigated. It has been found that only $T_{21}$ and $T_{22}$ are sensitive to the model deuteron wave function, in particular in the case of $\pi^0$-production above the $\Delta$-region, and that other asymmetries are not.Comment: 16 pages, 8 figures, accepted for publication in J. Phys. G: Nucl. Part. Phy

Polarization observables of the gamma d --> PiNN reaction in the Delta(1232)-resonance region

Polarization observables of the three charge states of the pion for the $\gamma d\to\pi NN$ reaction with polarized photon beam and/or oriented deuteron target are evaluated over the whole $\Delta$(1232)-resonance region adopting a nonrelativistic model based on time-ordered perturbation theory. Results for the $\pi$-meson spectra, linear photon asymmetry, vector and tensor target asymmetries are presented. Particular attention is given, for the first time, to double polarization asymmetries for which we present results for $T_{20}^{\ell}$ and $T_{2\pm 2}^{\ell}$. We found that all other double polarization asymmetries of photon and deuteron target are vanished.Comment: 17 Pages, 8 Figures, accepted for publication in Int. J. Mod. Phys.

Review of Polarization Observables in Incoherent Pion Photoproduction on the Deuteron

Polarization observables in incoherent pion photoproduction from the deuteron are investigated in the energy region from p-threshold up to the D (1232)-resonance with inclusion of all leading pNN effects. Formal expressions for polarization observables are derived and described by various beam, target and beam-target asymmetries for polarized photons and/or polarized deuterons. For the elementary pion photoproduction operator on the free nucleon, a realistic effective Lagrangian approach is used which includes seven nucleon resonances, in addition to Born and vector-meson exchange terms. The interactions in the final two-body subsystems are taken from separable representations of realistic potentials. Results are given for the unpolarized cross sections, the doubly polarized cross sections for parallel and antiparallel helicity states, the linear photon asymmetry, the double polarization E-asymmetry and, the vector and tensor deuteron asymmetries for the gd →p−pp, gd →p+nn, and gd →p0np channels. The contributions to the spin asymmetry and the Gerasimov-Drell-Hearn (GDH) integral from separate channels are evaluated by explicit integration up to a photon lab-energy of 350 MeV. Effects of final-state interaction are investigated and their role in these observables are found to be significant, specially for p0 production. The extracted results are compared with available experimental data and predictions of other works, and a satisfactory agreement is obtained. The sensitivity of the g d →pNN results to the elementary gN →pN operator is also investigated and a considerable dependence is found. This indicates that it can serve as a filter for different elementary operators. We expect that the results presented here may be useful to interpret the recent measurements from the high-intensity and high duty-factor electron accelerators MAMI, ELSA, Jefferson Lab, LEGS, and MAX-Lab