Soft diffractive high energy scattering and form factors in nonperturbative QCD

Abstract

In this work we study soft high energy reactions in the framework of nonperturbative models. Using a functional integral approach we derive the scattering amplitudes, which are governed by expectation values of light-like Wegner-Wilson loops and lines, which then are then evaluated in the model of the stochastic vacuum. We describe mesons in a simple quark-antiquark picture, for baryons we assume a quark-diquark structure, as hadronic wave functions we apply a Wirbel-Stech-Bauer ansatz. In the following we calculate integrated and differential cross sections from the scattering amplitudes, as well for elastic and diffractive proton-proton as for proton-pion scattering at high centre of mass energies and small momentum transfers and compare to experimental data. Depending on the symmetry of the respective final state we get either C=P=+1 (pomeron) oder C=P=-1 (odderon) exchange. Furthermore we calculate the isovector form factors of the proton and the pion at space-like momentum transfers. In the final chapter we use a dispersion approach to calculate the pion form factor at time-like momentum transfers and determine the masses and coupling constants of the rho- and omega-mesons from a comparison to experimental data.