Measurement of the Proton Structure Function F_2 at low Q^2 in QED Compton Scattering at HERA

TL;DR

This paper reports the measurement of the proton structure function F_2 at very low Q^2 using QED Compton scattering data from HERA, extending the kinematic range of previous experiments and confirming consistency with fixed target results.

Contribution

It introduces a novel method to access low Q^2 regions of F_2 using QED Compton scattering at HERA, covering a previously unexplored kinematic range.

Findings

Results agree with fixed target lepton-nucleon scattering measurements.

Extended the measurement range of F_2 to Q^2 down to 0.5 GeV^2.

Provided new data in a previously unmeasured kinematic region.

Abstract

The proton structure function F_2(x,Q^2) is measured in inelastic QED Compton scattering using data collected with the H1 detector at HERA. QED Compton events are used to access the kinematic range of very low virtualities of the exchanged photon, Q^2, down to 0.5 GeV^2, and Bjorken x up to \sim 0.06, a region which has not been covered previously by inclusive measurements at HERA. The results are in agreement with the measurements from fixed target lepton-nucleon scattering experiments.