Intercepts of the non-singlet structure functions

Abstract

Infrared evolution equations for small-x behaviour of the non-singlet structure functions f NS 1 and g NS 1 are obtained and solved in the next-to-leading approximation, to all orders in α s , and including running α s effects. The intercepts of these structure functions, i.e. the exponents of the power-like small-x behaviour, are calculated. A detailed comparison with the leading logarithmic approximation (LLA) and DGLAP is made. We explain why the LLA predictions for the small-x dependence of the structure functions may be more reliable than the prediction for the Q 2 dependence in the range of Q 2 explored at HERA.

Non-singlet structure functions: Combining the leading logarithms resummation at small-x with DGLAP

“…In contrast to the DGLAP parametrization α s = α s (k 2 ⊥ ), we used in Refs. [7] another parametrization where the argument of α s in the quark ladders is given by the time-like virtualities of the intermediate gluons. Arguments in favor of such a parametrization were given in Ref.…”

“…In the present paper we use our previous results [7,8] to show that the impact of the high-order corrections on the Q 2 and x -evolutions of the non-singlet structure functions is indeed quite sizable at available values of x. We also show that the reason for the success of phenomenological analysis of the data based on DGLAP at x < 10 −2 is related to the sharp x -dependence assumed for the initial parton densities, which is able to mimic the role of high-order corrections.…”

Treatment of the QCD coupling in high energy processes

“…On the contrary, the treatment of α s of Ref. [7] is valid for the evolution of DIS structure functions at small x and for other high energy QCD processes in the Regge kinematics. The paper is organised as follows: in sect 2 we discuss the treatment of α s in elementary parton processes.…”

“…[1] - [6], we have suggested [7] a quite different treatment of α s in the evolution equations for the non-singlet structure functions at small x. It is interesting that when the argument of α s is discussed in ref [8], the first assumptions about the argument look similar to Eqs.…”

Diffractive vector meson production

“…A summary of the high precision experimental data on the ratio of polarized, helicity, g 1 (x, Q 2 ), to unpolarized, F 1 (x, Q 2 ), proton structure function is shown in Fig. 23, the important point is that the effects of unnatural parity exchange vanish at small x, for pQCD arguments in favor of that see [273][274][275]. [272] are compared to the expectations from Eq.…”