The Running BFKL: Precocious Asymptopia for Charm and the $dF_{2}/d\log Q^2$ - Puzzle

Abstract

The running BFKL equation gives rise to a series of moving poles in the complex $j$-plane. The first nodes for all subleading solutions (color dipole cross sections) accumulate at $r_1\sim 0.1 fm$.Therefore the processes dominated by the dipole sizes $r\sim r_1 $ are free of subleading BFKL corrections. An example - the leptoproduction of charm. The calculated $F_2^{cc}$ is exhausted by the leading BFKL pole and gives a perfect description of the experimental data. The logarithmic slope of the subleading structure functions, $dF_2^{(n)}/d\log Q^2$, at small $Q^2$ is small compared to $dF_2^{(0)}/d\log Q^2$ due to the presence of nodes. This observation provides an explanation for the observed $x$/$Q^2$ dependence of the derivative of the proton structure function $dF_2/d\log Q^2$.