The interaction of an η-meson with two nucleons is studied within a three-body approach. The major features of the ηN N -system in the low-energy region are accounted for by using a s-wave separable ansatz for the two-body ηN -and N N -amplitudes. The calculation is confined to the (J π ; T ) = (0 − ; 1) and (1 − ; 0) configurations which are assumed to be the most promising candidates for virtual or resonant ηN N -states. The eigenvalue three-body equation is continued analytically into the nonphysical sheets by contour deformation. The position of the poles of the three-body scattering matrix as a function of the ηN -interaction strength is investigated. The corresponding trajectory, starting on the physical sheet, moves around the ηN N three-body threshold and continues away from the physical area giving rise to virtual ηN N -states. The search for poles on the nonphysical sheets adjacent directly to the upper rim of the real energy axis gives a negative result. Thus no low-lying s-wave ηN N -resonances were found. The possible influence of virtual poles on the low-energy ηN N -scattering is discussed.PACS numbers: 13.60. Le, 21.45.+v, 25.20.Lj * Supported by the Deutsche Forschungsgemeinschaft (SFB 443)

The contribution of incoherent single pion photoproduction to the spin response of the deuteron, i.e., the asymmetry of the total photoabsorption cross section with respect to parallel and antiparallel spins of photon and deuteron, is calculated over the region of the ∆-resonance with inclusion of final state N Nand πN -rescattering. Sizeable effects, mainly from N N -rescattering, are found leading to an appreciable reduction of the spin asymmetry. Furthermore, the contribution to the Gerasimov-Drell-Hearn integral is explicitly evaluated by integration up to a photon energy of 550 MeV. Final state interaction reduces the value of the integral to about half of the value obtained for the pure impulse approximation.

The optical potential approach for low-energy scattering of mesons on three-body nuclei is compared to an exact treatment of the 3N system using four-body scattering theory with separable interactions in s waves only. The higher-order terms including the interaction of the struck nucleon with the surrounding nuclear medium and virtual target excitations in between successive scatterings are found to cause important corrections. Effects of final state interaction in photoproduction on 3 H and 3 He are also studied and sizable contributions beyond the optical model approach are found.

The intrinsic electromagnetic nuclear meson exchange charge and current operators arising from a separation of the center-of-mass motion are derived for a one-boson-exchange model for the nuclear interaction with scalar, pseudoscalar and vector meson exchange including leading order relativistic terms. Explicit expressions for the meson exchange operators corresponding to the different meson types are given in detail for a two-nucleon system. These intrinsic operators are to be evaluated between intrinsic wave functions in their center-of-mass frame.Comment: 54 pages revtex, no figure

Inclusive electrodisintegration of the deuteron with polarized beam and target is investigated in detail. The additional polarization form factors are derived and their decomposition into multipoles is given. The sensitivity of these form factors to the potential model, to subnuclear degrees of freedom, and to electromagnetic form factors is studied in difFerent kinematical regions.