Zwei-Photon-Beiträge zur elastischen Elektron-Nukleon-Streuung im Skyrme-Modell

The most important goal of this work is the calculation of the contribution arising from the anomaly of QCD to the inelastic electron-proton scattering. Based on the Skryme model the protons are realized as soliton solutions in effective chiral theories. The next to leading order contribution to the cross section is given by the interference between the one- and two-photon exchange. The latter contains an ultraviolet divergence, which is renormalized by a local effective counterterm. This counterterm contributes to the width of the neutral pion decay which determines the finite part of the counterterm coefficient. The affect of the anomaly to the Rosenbluth separation of the electromagnetic form factors as well as the discrepance regarding the polarization measurements is extensively discussed within the Skyrme model. In addition, the correction as expected from the effective two-photon coupling of the non-linear-sigma model is estimated.