0 Anatomy of the differential gluon structure function of the proton from the experimental data on F 2 p ( x , Q 2 )

Anatomy of the differential gluon structure function of the proton from the experimental data on F 2p (x, Q 2) 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 parameteriza-tions 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 ∆ hard ∼ 0.4.