Consequences of t-channel unitarity for the interaction of real and virtual photons at high energies

Abstract

We analyze the consequences of t-channel unitarity for photon cross sections and show what assumptions are necessary to allow for the existence of new singularities at $Q^2=0$ for the ${\hat{I}}^{3}p$ and ${\hat{I}}^3{\hat{I}}^3$ total cross sections. For virtual photons, such singularities can in general be present, but we show that, apart from the perturbative singularity associated with $ γ^{*}γ^{*}\to q\bar q $, no new ingredient is needed to reproduce the data from LEP and HERA, in the Regge region.

10 pages, LaTeX2e with kluwer.sty, 7 figures. Talk presented at the Second International "Cetraro" Workshop & NATO Advanced Research Workshop "Diffraction 2002", Alushta, Crimea, Ukraine, August 31 - September 6, 2002