First Measurements of FL at Low Bjorken x

TL;DR

This paper reports the first measurements of the proton structure function FL at low Bjorken x, using data from HERA experiments, and compares results with QCD and dipole model predictions.

Contribution

It provides the first experimental measurements of FL at low x, validating theoretical models in this kinematic region.

Findings

Measurements are consistent with higher order QCD predictions.

Results agree with dipole model calculations.

Data collected at different proton beam energies.

Abstract

The first measurements of the longitudinal proton structure function FL in deep inelastic positron-proton scattering at low Bjorken x are described. Theoretical predictions in higher order QCD and using dipol model calculations are consistent with the measurements. The data were taken by the HERA experiments H1 and ZEUS in a series of runs with different proton beam energies in 2007.