New insights into the spin structure of the nucleon

TL;DR

This paper uses a covariant effective field theory with explicit spin-3/2 degrees of freedom to analyze the nucleon's low-energy spin structure, providing parameter-free predictions and highlighting the need for higher-order calculations.

Contribution

It introduces a third-order small scale expansion approach with explicit Delta-resonance degrees of freedom to improve understanding of nucleon spin structure.

Findings

Improved description of nucleon spin structure at finite photon virtualities

Parameter-free predictions for spin-polarizabilities and moments

Identification of the need for fourth-order calculations

Abstract

We analyze the low-energy spin structure of the nucleon in a covariant effective field theory with explicit spin-3/2 degrees of freedom to third order in the small scale expansion. Using the available data on the strong and electromagnetic width of the Delta-resonance, we give parameter-free predictions for various spin-polarizabilities and moments of spin structure functions. We find an improved description of the nucleon spin structure at finite photon virtualities for some observables and point out the necessity of a fourth order calculation.