Probing the Parton Densities of Virtual Photons at ep Colliders
  The feasibility of an experimental determination of the parton distributions of virtual photons at high energy $ep$ colliders is studied in the context of the DESY-HERA collider. Recently proposed parton densities of virtual photons are utilized to evaluate the appropriate production processes and their relevant kinematical regions. It is demonstrated that high $E_T$ jet production with $E_T\,\simeq 5-7\, {\rm{GeV}}$ and $b\bar{b}$ production can probe the parton distributions of virtual photons up to virtualities of a few ${\rm{GeV}}^2$. A useful leading order parametrization of our proposed photonic parton densities, suitable for further studies of these issues, is presented. 
M. Gluck, E. Reya, M. Stratmann (Univ. Dortmund)