Resolved photon and multi-component model for ${\gamma }^{\ast }$p and ${\gamma }^{\ast }{\gamma }^{\ast }$ scattering at high energies

We generalize our previous model for ${\gamma }^{\ast }p$ scattering to $\gamma \gamma$ scattering. In the latter case the number of components naturally grows. When using the model parameters from our previous ${\gamma }^{\ast }p$ analysis the model cross section for $\gamma \gamma$ scattering is larger than the corresponding LEP2 experimental data by more than a factor of two. However, performing a new simultaneous fit to ${\gamma }^{\ast }p$ and $\gamma \gamma$ total cross section we can find an optimal set of parameters to describe both processes. We propose new measures of factorization breaking for $\gamma^* \gamma^*$ collisions and present results for our new model.