A Measurement of the Proton Structure Function F_2(x,Q^2) at Low x and Low Q^2 at HERA

TL;DR

This paper reports measurements of the proton structure function F_2(x,Q^2) at very low x and Q^2 using HERA data, extending the kinematic range and comparing results with phenomenological models.

Contribution

It provides new measurements of F_2 at lower x and Q^2 than previous experiments, enhancing understanding of proton structure in this regime.

Findings

F_2 increases as x decreases, but less steeply at low Q^2.

Extended kinematic reach by a factor of 5 compared to previous data.

Comparison with models shows varying agreement at low Q^2.

Abstract

The results of a measurement of the proton structure function F_2(x,Q^2)and the virtual photon-proton cross section are reported for momentum transfers squared Q^2 between 0.35 GeV^2 and 3.5 GeV^2 and for Bjorken-x values down to 6 10^{-6} using data collected by the HERA experiment H1 in 1995. The data represent an increase in kinematic reach to lower x and Q^2 values of about a factor of 5 compared to previous H1 measurements. Including measurements from fixed target experiments the rise of F_2 with decreasing x is found to be less steep for the lowest Q^2 values measured. Phenomenological models at low Q^2 are compared with the data.