Rise of the DIS structure function F_L at small x caused by double-logarithmic contributions

Abstract

We present calculation of F_L in the double-logarithmic approximation and demonstrate that the synergic effect of the factor 1/x from the \alpha_s^2-order and the steep x-dependence of the totally resummed double logarithmic contributions of higher orders ensures the power-like rise of F_L at small x and arbitrary Q^2.

Comments: 19 pp, 2 figs. Comparison with DGLAP and BFKL is presented in more detail, misprints corrected, some refs added