Spin Sum Rules at Low $Q^2$

TL;DR

This paper reviews recent experimental data on nucleon spin structure at low momentum transfer, verifying some sum rules and highlighting discrepancies with theoretical models, especially in spin polarizability predictions.

Contribution

It provides new experimental results on neutron spin sum rules and polarizabilities at low to intermediate $Q^2$, and compares them with theoretical predictions, revealing notable disagreements.

Findings

Burkhardt-Cuttingham Sum Rule verified within uncertainties

Discrepancies observed between measured spin polarizabilities and Chiral Perturbation Theory

Preliminary results on first moments at very low $Q^2$ presented

Abstract

Recent precision spin-structure data from Jefferson Lab have significantly advanced our knowledge of nucleon structure at low $Q^2$. Results on the neutron spin sum rules and polarizabilities in the low to intermediate $Q^2$ region are presented. The Burkhardt-Cuttingham Sum Rule was verified within experimental uncertainties. When comparing with theoretical calculations, results on spin polarizability show surprising disagreements with Chiral Perturbation Theory predictions. Preliminary results on first moments at very low $Q^2$ are also presented.