The ratio of sigma_L/sigma_T in DIS at low x

TL;DR

This paper predicts that the ratio of longitudinal to transverse photoabsorption cross sections in deep inelastic scattering at low x is approximately 0.5 at high Q^2, based on helicity independence assumptions.

Contribution

It introduces a theoretical prediction for R(W^2,Q^2) in DIS at low x under specific helicity independence assumptions.

Findings

R(W^2,Q^2) ≈ 0.5 at large Q^2

Testable predictions for upcoming measurements

Supports helicity independence hypothesis

Abstract

Assuming helicity independence for q-qbar scattering in the color-dipole picture, or, equivalently proportionality of sea quark and gluon distributions, we find R(W^2,Q^2) = 0.5 (approximately) at large Q^2, where R(W^2,Q^2) denotes the ratio of the longitudinal and transverse photoabsorption cross sections. The forthcoming direct measurements of R(W^2,Q^2) allow one to test the underlying hypotheses.