Twist expansion of the nucleon structure functions,F2, andFL, in the DGLAP improved saturation model

Abstract

Higher twist effects in the deeply inelastic scattering are studied. We start with a short review of the theoretical results on higher twists in QCD. Within the saturation model we perform a twist analysis of the nucleon structure functions ${F}_{T}$ and ${F}_{L}$ at small value of the Bjorken variable $x$. The parameters of the model are fitted to the HERA ${F}_{2}$ data, and we derive a prediction for the longitudinal structure function ${F}_{L}$. We conclude that for ${F}_{L}$ the higher twist corrections are sizable whereas for ${F}_{2}={F}_{T}+{F}_{L}$ there is a nearly complete cancellation of twist-4 corrections in ${F}_{T}$ and ${F}_{L}$. We discuss a few consequences for future LHC measurements.