Nuclear effects on the longitudinal structure function at small x

TL;DR

This paper investigates how nuclear effects influence the longitudinal structure function at small x in deep inelastic scattering, highlighting the relationship with gluon distributions and the importance of future experimental sensitivity.

Contribution

It demonstrates the correlation between nuclear effects on the longitudinal structure function and gluon distributions, and assesses the experimental sensitivity needed to improve nuclear gluon knowledge.

Findings

Nuclear effects on F_L closely follow those on gluon distributions.

Uncertainties from current data can be propagated to future measurements.

Assumption that F_L/F_2 ratio is independent of nuclear size introduces uncertainties.

Abstract

We discuss the longitudinal structure function in nuclear DIS at small $x$. We work within the framework of universal parton densities obtained in DGLAP analyses at NLO. We show that the nuclear effects on the longitudinal structure function closely follow those on the gluon distribution. The error analyses available from newest sets of nuclear PDFs also allow to propagate the uncertainties from present data. In this way, we evaluate the minimal sensitivity required in future experiments for this observable to improve the knowledge of the nuclear glue. We further discuss the uncertainties on the extraction of $F_2$ off nuclear targets, introduced by the usual assumption that the ratio $F_L/F_2$ is independent of the nuclear size. We focus on the kinematical regions relevant for future lepton-ion colliders.