On the scaling properties of the total γp cross section

We perform a detailed analysis on the scaling properties of the total γ∗p cross section, σγ∗p. We write the cross section as a product of two functions W and V representing, respectively, the dynamical degrees of freedom and the contribution from the valence partons. Analyzing data from HERA and fixed target experiments we find that V is nearly independent of Q and concentrated at large x, while W carries all the information on the Q evolution of γ∗p. We define the reduced cross section σ̃γ∗p ≡ W = σγ∗p/V , and show that it is very close to a generalized homogeneous function. This property gives rise to geometric scaling not only for small x, but for all the current measured kinematic plane. As a consequence of our Ansatz we also obtain a compact parameterization of σγ∗p describing all data above Q 2 = 1 GeV.