Nucleon spin sum rules: higher twist coefficients extraction

Abstract

We present the analysis of the lower moment of spin-dependent proton structure function up to N3LO order which is now available in the theoretical treatment of QCD correction. By using the standard perturbation theory, PT, and the modified perturbation theory with correct analytic properties, APT, we extract values of higher-twist coefficients and of the singlet axial charge from fresh low-energy Jefferson Lab data. We find that the analytical approach provides a better convergence of the higher twist and higher order corrections series than the standard PT description. We demonstrate that the use of the APT allows to achieve a good quantitative description of the Jefferson Lab data down to the momentum transfer of about the QCD scale parameter.