Q 2 evolution of parton distributions at small values of x: Effective scale for combined H1 and ZEUS data on the structure function F 2

Abstract

An expression for the structure function F 2 in the form of Bessel functions at small values of the Bjorken variable x is used. This expression was derived for a flat initial condition in the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations. The argument of the strong coupling constant was chosen in such a way as to annihilate the singular part of the anomalous dimensions in the next-to-leading-order of perturbation theory. This choice, together with the frozen and analytic versions of the strong coupling constant, is used to analyze combined data of the H1 and ZEUS Collaborations obtained recently for the structure function F 2 .

Bjorken polarized sum rule and infrared-safe QCD couplings

“…The latter probably incorporate a part of the higher-twist contributions (which are rather cumbersome [49]) into (formally) the leading-twist contribution for small x range at moderately small Q 2 values ( 1 GeV 2 ) (see Ref. [50] and more recent studies [51] of the precise combined H1 and ZEUS data [52] for the DIS structure function F 2 ).…”

Parametrizations of Collinear and kT-Dependent Parton Densities in Proton

“…The generalized DAS approach has been successfully used to fit the experimental data for F 2 and F c 2 SFs (see Refs. [52,[55][56][57][58][59][60][61][62], respectively). In addition, it helps to extract gluon density and F L SF from experimental data of F 2 and its derivative with respect to Q 2 (see [63,64] and [65][66][67], respectively), to estimate the charm part of F L [68] and, finally, it leads to useful links between SFs [69][70][71].…”