The Color Dipole Picture and the ratio of R(W, Q) = sigma L/sigma T

TL;DR

This paper predicts a specific ratio of longitudinal to transverse photon cross sections in deep inelastic scattering, based on the color dipole model, which can be tested with upcoming HERA data.

Contribution

It introduces a prediction for the ratio R(W, Q) in deep inelastic scattering considering the transverse size reduction of q q-bar fluctuations.

Findings

Predicted R(W, Q) = 0.375 at high Q2 and small x

FL/F2 ratio predicted to be 0.27 under the model

Experimental data from HERA can test this prediction

Abstract

The transverse size of q q-bar fluctuations of the longitudinal photon is reduced relative to the transverse size of q q-bar fluctuations of the transverse photon. This implies R(W2, Q2) = 0.375 or, equivalently, FL/F2 = 0.27 at x<<0.1 and Q2 sufficiently large, while R(W2, Q2) = 0.5, if this effect is not taken into account. Forthcoming experimental data from HERA will allow to test this prediction.