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

TL;DR

This paper presents precise measurements of the gamma-proton cross section at HERA across different Q^2 regimes, confirming theoretical predictions and extracting the gluon density in the proton.

Contribution

It provides new experimental data on F2 and FL structure functions and the gamma-p cross section, bridging low and medium Q^2 regimes with theoretical agreement.

Findings

Total gamma-p cross section agrees with soft Pomeron prediction at low Q^2

F2 and FL structure functions are well described by NLO pQCD at medium Q^2

Gluon density in the proton extracted from F2 scaling violations

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.