On the scaling properties of the total γ* p 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 independent of Q2 and concentrated at large x, while W carries all the information on the Q2 evolution of σγ*p. We define the reduced cross section σγ*p = W = σγ*p/V, and show that it is very close to a generalized homogeneous function. This property gives rise to geometric scaling for σγ*p, and it also explains the known geometric scaling of σγ*p at low x. As a consequence of our Ansatz, we also obtain a compact parameterization of a σγ*p describing all data above Q2 = 1 GeV2. (Author)