Moments of the longitudinal proton structure function F_L from global data in the Q^2 range 0.75-45.0 (GeV/c)^2

TL;DR

This paper extracts the first three moments of the proton's longitudinal structure function F_L over a broad Q^2 range using world data, revealing discrepancies with theoretical models and indicating potential higher twist effects or a larger gluon distribution.

Contribution

It provides the first determination of these moments over a large Q^2 range with minimal extrapolation uncertainties, incorporating new low-x and high-x data.

Findings

Leading twist parameterizations underestimate the moments

Higher moments show larger discrepancies

Results suggest significant higher twist effects or larger gluon distribution

Abstract

We present an extraction of the lowest three moments of the proton longitudinal structure function F_L from world data between Q^2 = 0.75 and 45 (GeV/c)^2. The availability of new F_L data at low Bjorken x from HERA and at large x from Jefferson Lab allows the first determination of these moments over a large Q^2 range, relatively free from uncertainties associated with extrapolations into unmeasured regions. The moments are found to be underestimated by leading twist structure function parameterizations, especially for the higher moments, suggesting either the presence of significant higher twist effects in F_L and/or a larger gluon distribution at high x.