Role of the singular factors in the standard fits for initial parton densities

Abstract

Total resummation of double- and single- logarithms of x contributing to the spin-dependent structure function g_1 ensures its steep rise at small $x$. In the asymptotic limit x ->0, the resummation leads to the Regge behavior of g_1 and allows to calculate the non-singlet and singlet intercepts of g_1. DGLAP lacks such a resummation but suggests special phenomenological fits for the initial parton densities such that the singular factors x^{-\alpha} in the fits mimic the resummation and also provide g_1 with the steep (power-like) rise at the small-x region. Accounting for the total resummaton of logarithms of x allows to drop the singular factors in the fits and leads to remarkable simplifications of the fits.

Comments: Invited talk at the XI Workshop on High Energy Spin Physics, Dubna, Russia, September 27 - October 1, 2005, 4 pages, LaTeX