The Ratio of sigma_L(W2, Q2)/sigma_T(W2, Q2) in the Color Dipole Picture

TL;DR

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

Contribution

It provides a theoretical prediction for the ratio R(W^2, Q^2) in the color dipole picture, accounting for the reduced transverse size of longitudinal photon fluctuations.

Findings

Predicted R(W^2, Q^2) = 0.375 at high Q^2 and small x

F_L/F_2 ratio predicted as 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(W^2, Q^2) = 0.375 or, equivalently, F_L(W^2,Q^2)/F_2(W^2,Q^2) = 0.27 for x = Q^2/W^2 << 1 and Q^2 sufficiently large, while R(W^2, Q^2) = 0.5, if this effect is not taken into account. Forthcoming experimental data from HERA will allow to test this prediction.