Longitudinal structure function $F_L$ at low $Q^2$ and low $x$ with model for higher twist: an update

TL;DR

This paper updates a model for the longitudinal structure function $F_L$ at low $x$ and $Q^2$, incorporating higher twist effects and kinematic constraints, to better interpret upcoming Electron-Ion Collider data.

Contribution

The paper introduces an improved model for $F_L$ that includes higher twist contributions and is validated against current data, enhancing understanding at low $Q^2$ and low $x$.

Findings

Model aligns with existing data at low $Q^2$ and $x$

Incorporates $Q^4$ behavior as $Q^2 o 0$

Provides a framework for future EIC analyses

Abstract

A reanalysis of the model for the longitudinal structure function $F_L (x,Q^2)$ at low $x$ and low $Q^2$ was undertaken, in view of the advent of the EIC. The model is based on the photon-gluon fusion mechanism suitably extrapolated to the region of low $Q^2$. It includes the kinematic constraint $F_L\sim Q^4$ as $Q^2\rightarrow$ 0 and higher twist contribution which vanishes as $Q^2 \rightarrow \infty$. Revised model was critically updated and compared to the presently available data.