Nucleon spin structure at low momentum transfers

TL;DR

This paper refines a QCD-inspired model for the nucleon spin structure at low momentum transfers by incorporating higher order corrections and analytic perturbation theory, achieving accurate data descriptions across a wide Q^2 range.

Contribution

It introduces an improved model for the Q^2-dependence of the GDH sum rule, incorporating higher order corrections and analytic methods to extend applicability to low Q^2.

Findings

Good agreement with recent experimental data across all Q^2.

Matching point between different Q^2 regimes shifted to near Lambda_QCD.

Enhanced understanding of nucleon spin sum rules at low momentum transfers.

Abstract

The generalized Gerasimov-Drell-Hearn (GDH) sum rule is known to be very sensitive to QCD radiative and power corrections. We improve the previously developed QCD-inspired model for the $Q^2$-dependence of the GDH 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 $\Gamma_1^{p}(Q^2)$ and on the Bjorken sum rule $\Gamma_1^{p-n}(Q^2)$. By using the singularity-free analytic perturbation theory we demonstrate that the matching point between chiral-like positive-$Q^2$ expansion and QCD operator product $1/Q^2$-expansion for the nucleon spin sum rules can be shifted down to rather low $Q\simeq\Lambda_{QCD}$ leading to a good description of recent proton, neutron, deuteron and Bjorken sum rule data at all accessible $Q^2$.