Low-x contribution to the Bjorken sum rule within unified $ln^2x+$LO DGLAP approximation

Abstract

The small-$x$ contributions to the Bjorken sum rule within unified picture $ln^2x+$LO DGLAP for different input parametrisations $g_1^{NS}(x,Q_0^2)$ are presented. Theoretical predictions for $\int_{0}^{0.003} g_1^{NS}(x,Q^2=10) dx$ are compared with the SMC small-$x$ data. Rough estimation of the slope $\lambda$, controlling the small-$x$ behaviour of $g_1^{NS}\sim x^{-\lambda}$ from the obtained results and SMC data is performed. The crucial role of the running coupling $\alpha_s=\alpha_s(Q^2/z)$ at low-$x$ is taken into account.