γ*-γ* Scattering: Saturation and Unitarization in the BFKL Approach

In this paper γ*-γ* scattering with large, but more or less equal virtualities of two photons is discussed using BFKL dynamics, emphasizing the large impact parameter behavior (bt) of the dipole-dipole amplitude. It is shown that the non-perturbative contribution is essential to fulfill the unitarity constraints in the region of bt >1/2 mπ, where mπ is pion mass. The saturation and the unitarization of the dipole-dipole amplitude is considered in the framework of the Glauber-Mueller approach. The main result is that we can satisfy the unitarity constraints introducing the non-perturbative corrections only in initial conditions (Born amplitude). (author)