Low Q^2 Structure Function Measurements

TL;DR

This paper reports new measurements of the proton structure function F_2 at low Q^2 and x, showing a significant rise with decreasing x, consistent with QCD predictions and models involving pomeron exchange.

Contribution

It provides the first detailed measurements of F_2 in the low Q^2 region and compares the results with QCD fits and pomeron exchange models.

Findings

F_2 increases with decreasing x at low Q^2

Data aligns with NLO QCD fits and DGLAP evolution

Gluon density rises at low x

Abstract

New Results on the measurement of the proton structure function F_2(x,Q^2) are reported for momentum transfers squared Q^2 >= 1.5 GeV^2 and Bjorken x >= 3.5 10^{-5} using data collected by the HERA experiments H1 and ZEUS in 1994. F_2 increases significantly with decreasing x, even in the lowest reachable Q^2 region. The data are well described by a Next to Leading Order QCD fit, and support within the present precision that the rise at low x within this Q^2 range is generated via the DGLAP evolution equations. A comparison with models based on pomeron exchange is also presented. The gluon density is extracted and observed to rise at low x.