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.

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 present a Regge-plus-resonance (RPR) description of the p(e, e ′ K + )Y processes (Y = Λ, Σ 0 ) in the resonance region. The background contributions to the RPR amplitude are constrained by the high-energy p(γ, K + )Y data. As a result, the number of free model parameters in the resonance region is considerably reduced compared to typical effective-Lagrangian approaches. We compare a selection of RPR model variants, originally constructed to describe KY photoproduction, with the world electroproduction database. The electromagnetic form factors of the intermediate N * s and ∆ * s are computed in the Bonn constituent-quark model. With this input, we find a reasonable description of the p(e, e ′ K + )Y data without adding or readjusting any parameters. It is demonstrated that the electroproduction response functions are extremely useful for fine-tuning both the background and resonant contributions to the reaction dynamics.

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Predictions for the electromagnetic form factors of the Λ, Σ and Ξ hyperons are presented. The numerical calculations are performed within the framework of the fully relativistic constituent-quark model developed by the Bonn group. The computed magnetic moments compare favorably with the experimentally known values. Most magnetic form factors GM (Q 2 ) can be parametrized in terms of a dipole with cutoff masses ranging from 0.79 to 1.14 GeV. PACS. 11.10.St Bound and unstable states; Bethe-Salpeter equations -12.39.Ki Relativistic quark model -13.40.Gp Electromagnetic form factors