Eur. Phys. J. C (2006) 47: 365-373
https://doi.org/10.1140/epjc/s2006-02566-x

Theoretical Physics

Investigating F_L(x,Q²) at fixed energy in the color dipole formalism

¹ Unidade de Bento Gonçalves, Universidade Estadual do Rio Grande do Sul (UERGS), CEP 97500, Bento Gonçalves, Brazil
² High Energy Physics Phenomenology Group, GFPAE, IF-UFRGS, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS, Brazil

^* e-mail: magnus@if.ufrgs.br

Received: 21 December 2005
Revised: 11 March 2006
Published online: 19 May 2006

Abstract

At small x, the structure function F_L(x,Q²) is driven by the gluon content of the nucleon target and consequently it can unravel the underlying QCD dynamics in that region. In this work, one studies its behavior on the photon virtuality Q² at fixed energy within the color dipole formalism for models considering parton saturation effects. The reason is that they resum a wide class of higher-twist contributions, which have an important influence on the F_L description towards low Q². It is shown that the geometric scaling property holds for the longitudinal cross section. Moreover, the effective anomalous dimension in the scaling dipole cross sections can be investigated by studing both the turn-over and the large Q² regions of the recent experimental measurements.