A novel determination of non-perturbative contributions to Bjorken sum rule

TL;DR

This paper refines the determination of non-perturbative effects in the Bjorken sum rule by applying the principle of maximum conformality to improve pQCD predictions and fitting high-twist contributions using low-energy models and experimental data.

Contribution

It introduces a scheme-and-scale independent pQCD approach using PMC and provides a novel fit of high-twist contributions to experimental data.

Findings

PMC eliminates renormalization scale dependence.

High-twist effects are significant at low and intermediate Q^2.

The new fit aligns well with JLab experimental data.

Abstract

In the present paper, we first give a detailed study on the pQCD corrections to the leading-twist part of BSR. Previous pQCD corrections to the leading-twist part derived under conventional scale-setting approach up to ${\cal O}(\alpha_s^4)$-level still show strong renormalization scale dependence. The principle of maximum conformality (PMC) provides a systematic way to eliminate conventional renormalization scale-setting ambiguity by determining the accurate $\alpha_s$-running behavior of the process with the help of renormalization group equation. Our calculation confirms the PMC prediction satisfies the standard renormalization group invariance, e.g. its fixed-order prediction does scheme-and-scale independent. In low $Q^2$-region, the effective momentum of the process is small and to have a reliable prediction, we adopt four low-energy $\alpha_s$ models to do the analysis. Our predictions show that even though the high-twist terms are generally power suppressed in high $Q^2$-region, they shall have sizable contributions in low and intermediate $Q^2$ domain. By using the more accurate scheme-and-scale independent pQCD prediction, we present a novel fit of the non-perturbative high-twist contributions by comparing with the JLab data.