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Review of Polarization Observables in Incoherent Pion Photoproduction on the Deuteron |
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PP: 527-548 |
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Author(s) |
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Eed M. Darwish,
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Abstract |
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| 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. |
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