Compton scattering off nucleons near threshold

The energy dependence of the magnetic polarizability β has been evaluated by use of the delta resonance in the s- and u-channel of the Compton scattering amplitude. It was the idea to extract the influence of higher order terms (higher than ω2, ω = |k| being the photon energy) in the analysis of the polarizability. The static paramagnetic polarizability βPara(0) has been substituted by an energy dependent βδPara(k) and the result is compared with experimental data.

Relativistic corrections to the Drell-Hearn-Gerasimov sum rule in the constitutent quark model

Relativistic corrections have been calculated for the Drell-Hearn-Gerasimov sum rule in the framework of the constituent-quark model. These corrections lead to additional absorption strength due to relativistic dipole currents in the case of a hyperfine interaction. The introduction of anomalous magnetic moments requires a subtraction of the dispersion integral at infinity. The additional effects of such anomalous moments, however, are numerically very small within the model.

Electronuclear sum rules

Contributions of internal nucleon structure to the nuclear charge and current operators

The relativistic pair current and contributions of nucleon isobars are evaluated in the constituent-quark model. Isovector charge and isoscalar current contributions change substantially compared to previous calculations. The magnetic form factor of the deuteron and the charge form factors of3He and3H are modifed significantly and the previously predicted large differences in the form factors of3He and3H are considerably reduced.

Pion Photoproduction on the Nucleon and Light Nuclei

Photo- and electroproduction of mesons are well suited tools to investigate the structure of hadrons. With the advent of electron accelerators with high current and large duty-factor, new classes of experiments including polarization degrees of freedom have become possible. Such investigations range from threshold production of mesons to detailed studies of nucleon resonances. In addition, there is the large field of meson production and propagation in the nuclear medium.

Dispersion Approach to Pion Photoproduction and GDH Sum Rule

Pion photoproduction has been analyzed in the framework of dispersion relations at constant t. The results for S-wave pion production at threshold and P-wave production in the Δ (1232) resonance region are presented and compared to the data and theoretical expectations. The predictions for the GDH sum rule are shown to be very sensitive to the threshold S-wave amplitude.

The Drell-Hearn-Gerasimov sum rule and the constituent quark model

The helicity structure function of the nucleon has been calculated for the constituent quark model and compared to the prediction of the Drell-Hearn-Gerasimov sum rule. The multipole decomposition of the sum rule shows large cancellations between different resonances. The small isoscalar-isovector contribution is related to the admixture of aD-state (“bag deformation”) in the nucleon's wave function. The calculations indicate a relatively slow saturation of this part of the sum rule with excitation energy.

The Drell-Hearn-Gerasimov Sum Rule

The Drell-Hearn-Gerasimov (DHG) sum rule relates the helicity structure of the photoabsorption cross section to the anomalous magnetic moment of the nucleon. It is based on Lorentz and gauge invariance, crossing symmetry, causality and unitarity. A generalized DHG sum rule my be derived for virtual photons. At low momentum transfer this generalized sum rule is saturated by the resonance region, at high momentum transfer it may be expressed by the parton spin distributions measured in deep inelastic scattering. The longitudinal-transverse interference determines the Cottingham sum rule, which is related to the electric and magnetic form factors over the whole range of momentum transfer.

General introduction to Compton scattering

Real and virtual Compton scattering has been and will be an important tool to study the structure of hadronic systems. We summarize the status of real Compton scattering and give an outlook at the new theoretical and experimental developments in the field of virtual Compton scattering.

3,3 resonance and Nucleon pole model forpp→ppπ0 andpp→pnπ+

The Nucleon pole and 3,3 resonance pole contributions are considered for the reactionspp→ppπ0 andpp→pnπ+ at low and medium incident proton energies. The total and various differential cross sections are calculated, also for polarized nucleons, and compared with experimental data.

"Table 6" of "Precise pion electroproduction in the p (e, e-prime pi+) n reaction at W = 1125-MeV"

Angle PHI(P=4) is the angle between the scattering plane (defined by 1 and 3 particles) and the reaction plane (defined by 4 and 5 particles).

"Table 4" of "Precise pion electroproduction in the p (e, e-prime pi+) n reaction at W = 1125-MeV"

Angle PHI(P=4) is the angle between the scattering plane (defined by 1 and 3 particles) and the reaction plane (defined by 4 and 5 particles).

"Table 2" of "Precise pion electroproduction in the p (e, e-prime pi+) n reaction at W = 1125-MeV"

Angle PHI(P=4) is the angle between the scattering plane (defined by 1 and 3 particles) and the reaction plane (defined by 4 and 5 particles).

"Table 5" of "Precise pion electroproduction in the p (e, e-prime pi+) n reaction at W = 1125-MeV"

Angle PHI(P=4) is the angle between the scattering plane (defined by 1 and 3 particles) and the reaction plane (defined by 4 and 5 particles).

"Table 3" of "Precise pion electroproduction in the p (e, e-prime pi+) n reaction at W = 1125-MeV"

Angle PHI(P=4) is the angle between the scattering plane (defined by 1 and 3 particles) and the reaction plane (defined by 4 and 5 particles).

"Table 1" of "Precise pion electroproduction in the p (e, e-prime pi+) n reaction at W = 1125-MeV"

Angle PHI(P=4) is the angle between the scattering plane (defined by 1 and 3 particles) and the reaction plane (defined by 4 and 5 particles).