Optimized QCD determination of the polarized Bjorken sum rule.

We discuss and improve the determination of polarized Bjorken sum rule $\Gamma_1$ in two different ways: phenomenological determination of $\Gamma_1^\text{exp}$ by means of integration of the spin structure function $g_1$ within the truncated moment approach; and the optimization of the truncated perturbation series for the coefficient function of the corresponding DIS process by means of the renormalization group. Both obtained values $\Gamma_1^\text{exp}$ and $\Gamma_1^\text{th}$ become closer to each other when processing COMPASS data. Meanwhile, this optimization approach is universal and can be applied to any of the DIS sum rules.