Quasifree eta photoproduction from nuclei and medium modifications of resonances

We investigate the sensitivity of the differential cross section, recoil nucleon polarization and the photon asymmetry to changes in the elementary amplitude, medium modifications of the resonance $(S_{11},D_{13})$ masses, as well as nuclear target effects. All calculations are performed within a relativistic plane wave impulse approximation formalism resulting in analytical expressions for all observables. The spin observables are shown to be unique tools to study subtle effects that are not accessible by only looking at the unpolarized differential cross section.Comment: 27 pages, 8 figures, Revtex, To be published in Phys. Rev.

Single and double π⁰-photoproduction from the deuteron

Photoproduction of neutral pions from the deuteron has been studied for incident photon energies from 200 MeV to 792 MeV with the TAPS detector at the Mainz MAMI accelerator. Total and differential cross sections covering the full angular range have been obtained for coherent and incoherent single pi(o)-photoproduction. Good agreement between model predictions and the data was found for the coherent process. The incoherent cross section in the energy region of the Delta(1232)-resonance is overesti- mated by existing models. A comparison to model predictions indicates that final state interaction effects are much more important than for the coherent reaction. However, the angular dependence of the data in the Delta-peak region follows the pattern expected from the dominant excitation of the M1+-multipole on the free nucleon. The energy and angular dependence of single pi(o)-photoproduction in the second resonance region is remarkably different from the reaction on the free proton, indicating a strong nuclear effect. Finally the total cross section for double pi(o)-photoproduction from the deuteron has been measured for the first time and was used to estimate the cross section for double pi(o)-photoproduction from the neutron