Anatomy of the differential gluon structure function of the proton from the experimental data onF2p(x,Q2)

Abstract

The use of the differential gluon structure function of the proton F(x, Q 2 ) introduced by Fadin, Kuraev and Lipatov in 1975 is called upon in many applications of small-x QCD. We report here the first determination of F(x, Q 2 ) from the experimental data on the small-x proton structure function F 2p (x, Q 2 ). We give convenient parameterizations for F(x, Q 2 ) based partly on the available DGLAP evolution fits (GRV, CTEQ & MRS) to parton distribution functions and on realistic extrapolations into soft region. We discuss an impact of soft gluons on various observables. The x-dependence of the so-determined F(x, Q 2 ) varies strongly with Q 2 and does not exhibit simple Regge properties. None the less the hard-to-soft diffusion is found to give rise to a viable approximation of the proton structure function F 2p (x, Q 2 ) by the soft and hard Regge components with intercepts ∆ sof t = 0 and ∆

Heavy quark photoproduction in thek⊥-factorization approach

“…We benefit from the results on the k ⊥ -factorization approach applied to ep collisions, in particular for the proton structure function, performed in Ref. [38]. There, it was verified that for not too high virtualities Q 2 (including photoproduction), a suitable approximation is x 2 = 2 x Bj .…”

Decomposition of the QCD string into dipoles and unintegrated gluon distributions

“…In contrast, the GBW unintegrated gluon distribution increases much faster as x decreases. [44], the derivative of the Glück, Reya, and Vogt (GRV) parametrization of xG p (x, Q 2 ) [51], and the Ivanov and Nikolaev (IN) approach [49]. Note that the GRV parametrization is only available for k 2 ⊥ ≥ 0.8 GeV 2 .…”

“…Ivanov and Nikolaev [49] have constructed a two-component (soft + hard) ansatz for the unintegrated gluon distribution of the proton…”

Exclusive coherent production of heavy vector mesons in nucleus-nucleus collisions at energies available at the CERN Large Hadron Collider

“…There a good agreement with available data on nuclear shadowing has been obtained. In the numerical calculations, we use an unintegrated gluon distribution of the proton that has been obtained from an analysis of HERA structure function data in [18].…”