Seminarium Teorii Oddziaływań Elementarnych

Standard Approach (SA) is based on the DGLAP evolution equations and the special fits for the initial parton densities including a large number of phenomenological parameters. SA accounts for the total resummation of logs of Q^2 and lacks the resummation of ln(1/x). In order to be consistent at small x, SA includes the singular factors in the fits. This factors ensure the steep rise (the Regge behavior) of the structure function g_1 at small x and mimic the resummation of ln(1/x). When the resummation is accounted for, the fits can be simplified down to normalization constants. The further advantage of our approach lays in analysis of DIS at small Q^2. Indeed, DGLAP cannot be applied to the region of small Q^2 presently studied by COMPASS collaboration. Contrary to it, our approach works in this kinematics and predicts a very week x-dependence of g_1 even at very small values of x. Instead, it is interesting to study the dependence of g_1 on the invariant energy. Experimental investigation of this dependence would allow one to estimate the ratio between the initial quark and gluon densities. At last, we investigate the infrared properties of g_1 at small. Doing so, we conclude that a part of the power ~1/(Q^2)^k corrections (they are usually attributed to the higher twists impact) in reality has the perturbative origin. We suggest simple formulae for the total resummation of such corrections. The use of can change a lot the conventional impact of the higher twists.