Spin Sum Rules and the Strong Coupling Constant at large distance

TL;DR

This paper discusses experimental measurements of spin sum rules at low momentum transfer, compares them with theoretical predictions, and explores how the Bjorken sum rule can define an effective strong coupling at various distances.

Contribution

It provides new experimental data on spin sum rules at low Q^2 and links these results to the definition of an effective strong coupling constant across distances.

Findings

Experimental results align with Chiral Perturbation Theory at low Q^2

The Bjorken sum rule helps define an effective strong coupling at all distances

Comparison of sum rules with theoretical models enhances understanding of strong force dynamics

Abstract

We present recent results on the Bjorken and the generalized forward spin polarizability sum rules from Jefferson Lab Hall A and CLAS experiments, focusing on the low $Q^2$ part of the measurements. We then discuss the comparison of these results with Chiral Perturbation theory calculations. In the second part of this paper, we show how the Bjorken sum rule with its connection to the Gerasimov-Drell-Hearn sum, allows us to conveniently define an effective coupling for the strong force at all distances.