On the behavior of $F_2$ and its logarithmic slopes

Abstract

It is shown that the CKMT model for the nucleon structure function F 2 , taken as the initial condition for the NLO evolution equations in perturbative QCD, provides a good description of the HERA data when presented in the form of the logarithmic slopes of F 2 vs x and Q 2 (Caldwell-plot), in the whole available kinematic ranges. Also the results obtained for the behavior of the gluon component of a nucleon are presented.

Scaling violations in the Q2 logarithmic derivative of F2

“…This was recently suggested by Caldwell [4], showing a rather complicated plot of ∂ ln Q 2 corresponding to Q 2 of about 3 GeV 2 and x < 5·10 −3 , in contrast to the behavior expected from GRV94 [23] at sufficiently small Q 2 and x. The problem with this presentation is that, as suggestive as it may seem, it does not discriminate between different dynamical interpretations [14,15,17,18,19,21]. It is, actually compatible with an overall data generator [24] as well as the latest pdfs which were adjusted to account for this observation.…”

“…There has also been a successful reproduction of the Caldwell plot by Kaidalov et al [19] within the framework of the CKMT model [20], and by Forshaw et al [21] using a colour dipole model formalism. We are of the opinion that fitting the Caldwell as well as the fixed W plots is a necessary first step, but a comparison with all the detailed measurements is essential to test the adequacy of a given model.…”

“…We conclude with a critical discussion and caution regarding attempts that have been made to determine the gluon saturation scale using data with highly correlated variables such as in the Caldwell and fixed W plots [4,6,18]. We also comment on the general problems associated with gluon saturation and screening corrections relating to other models which include SC [18,19,20,21].…”

Charm production in diffractive deep inelastic scattering

“…[13,14] that this is due to the fact that the size of the absorptive corrections decreases when Q 2 increases. This parameterization gives a good description of all existing data on γ * p total cross section in the region Q 2 ≤ 10 GeV 2 [24]. At larger Q 2 , effects due to QCD evolution become important.…”

“…with ∆(0) = 0.09663, d 0 = 1.9533 and d 1 = 1.1606 [24]. The Q 2 dependence of the effective Pomeron intercept is one of the main feature of the CKMT model.…”