Nonforward parton densities and soft mechanism for form factors and wide-angle Compton scattering in QCD

We argue that, at a moderately large momentum transfer - t less than or similar to 10 GeV2, hadronic form factors and wide-angle Compton scattering amplitudes are dominated by a mechanism corresponding to the overlap of soft wave functions. We show that the soft contribution in both cases can be described in terms of the same universal nonforward parton densities (ND's) F(x;t), which are the simplest hybrids of the usual parton densities and hadronic form factors. We propose a simple model for ND's possessing required reduction properties. Our model easily reproduces the observed magnitude and the dipole a dependence of the proton form factor F-1(p)(t) in the region 1 GeV2 <- t< 10 GeV2. Our results for the wide-angle Compton scattering cross section follow the angular dependence of existing data and are rather close to the data in magnitude. [S0556-2821(98)01321-6].