Nucleon spin structure at low momentum transfers

The generalized Gerasimov-Drell-Hearn sum rule is known to be very sensitive to QCD radiative and power corrections. We improve the previously developed QCD-inspired model for the Q2 dependence of the Gerasimov-Drell-Hearn sum rule. We take into account higher order radiative and higher-twist power corrections extracted from precise Jefferson Lab data on the lowest moment of the spin-dependent proton structure function Γ1p(Q2) and on the Bjorken sum rule Γ1p-n(Q2). By using the singularity-free analytic perturbation theory we demonstrate that the matching point between chiral-like positive-Q2 expansion and QCD operator product 1/Q2 expansion for the nucleon spin sum rules can be shifted down to rather low QΛQCD leading to a good description of recent proton, neutron, deuteron, and Bjorken sum rule data at all accessible Q2