We present an effective-Lagrangian description for forward-angle K + Λ photoproduction from the proton, valid for photon lab energies from threshold up to 16 GeV. The high-energy part of the amplitude is modeled in terms of t-channel Regge-trajectory exchange. The sensitivity of the calculated observables to the Regge-trajectory phase is investigated in detail. The model is extended towards the resonance region by adding a number of s-channel resonances to the t-channel background. The proposed hybrid "Regge-plus-resonance" (RPR) approach allows one to exploit the p(γ, K + )Λ data in their entirety, resulting in stronger constraints on both the background and resonance couplings. The high-energy data can be used to fix the background contributions, leaving the resonance couplings as the sole free parameters in the resonance region. We compare various implementations of the RPR model, and explore to what extent the description of the data can be improved by introducing the "new" resonances D 13 (1900) and P 11 (1900). Despite its limited number of free parameters, the proposed RPR approach provides an efficient description of the p(γ, K + )Λ dynamics in and beyond the resonance region.

At sufficiently large proton energies, Glauber multiple-scattering theory offers good opportunities for describing the final state interactions in electro-induced proton emission off nuclear targets. A fully unfactorized relativistic formulation of Glauber multiple-scattering theory is presented. The effect of truncating the Glauber multiple-scattering series is discussed. Relativistic effects in the description of the final-state interactions are found not to exceed the few percent level. Also the frequently adopted approximation of replacing the wave functions for the individual scattering nucleons by some average density, is observed to have a minor impact on the results when obtained in the independent-particle model. Predictions for the separated 4 He(e, e p) response functions are given in quasi-elastic kinematics and a domain corresponding with 1 Q 2 2 (GeV) 2 .

A study of γp → KΣ processes in an isobar model at tree level is reported. By comparing model calculations to the published SAPHIR data, we explore the possible role of different isospin I = 1 2 (N * ) and I = 3 2 (∆ * ) resonances in the reaction dynamics. In our analysis, the inclusion of the "missing" D13(1895) resonance does only slightly improve the global description of the Σ photoproduction data. More convincing signals for the presence of such a "missing" resonance emerged in the analysis of the isospin related γp → K + Λ reaction. Various implementations of the nonresonant part of the Σ photoproduction amplitude are presented. The sensitivity of the computed observables and extracted resonance parameters to the uncertainties inherent to the treatment of the non-resonant (background) diagrams are discussed.

An effective-Lagrangian framework for KΣ photoproduction from the proton is presented. The proposed model is applicable at forward kaon angles and photon lab energies from threshold up to 16 GeV. The high-energy part of the p(γ, K + )Σ 0 and p(γ, K 0 )Σ + amplitudes is expressed in terms of Regge-trajectory exchange in the t channel. By supplementing this Regge background with a number of s-channel resonances, the model is extended towards the resonance region. The resulting "Regge-plus-resonance" (RPR) approach has the advantage that the background contributions involve only a few parameters, which can be largely constrained by the high-energy data. This work compares various implementations of the RPR model, and explores which resonance contributions are required to fit the data presently at hand. It is demonstrated that, through the inclusion of one K and two K * trajectories, the RPR framework provides an efficient and unified description of the K + Σ 0 and K 0 Σ + photoproduction channels over an extensive energy range.

We discuss the role of hyperon resonances in the u-channel when modeling p γ, K + Λ processes in an effective Lagrangian approach. Without the introduction of hyperon resonances, one is forced to use soft hadronic form factors with a cutoff mass which is at best two times the kaon mass. After inclusion of the hyperon resonances in the u-channel, we obtain a fair description of the data with a cutoff mass of the order of 1.8 GeV.