F2p at low Q^2 and the total gamma-p cross section at HERA

Abstract

New precise measurements of the neutral current cross section at HERA are presented in different Q^2 regimes. In the photoproduction limit the total gamma-p cross section is found to be in agreement with the universal soft Pomeron prediction. At medium scales 1.5 < Q^2 < 150 GeV^2 both the F_2 and the F_L structure functions are determined. These data are well described by NLO pQCD. The gluon density in the proton has been extracted from the scaling violation of F_2 at low x. The transition between the two regimes occurs at around Q^2=1 GeV^2.