Small -x behavior of the non-singlet and singlet structure functions g_1

Abstract

Explicit expressions for the non-singlet and singlet structure functions g_1 at the small $x$-region are obtained. They include the total resummation of double-logarithmic contributions and accounting for the running QCD coupling effects. We predict that both the non-singlet and singlet g_1 asymptotically ~ x^{- \Delta}, with the singlet intercept = 0.86 and being more than twice larger than the non-singlet intercept = 0.4. The impact of the initial quark and gluon densities on the sign of g_1 at x << 1 is discussed.

Comments: Talk given at Xth Workshop on high energy spin physics, Dubna, Russia, September,16-20, 2003. LateX 9pp, 4 figs