A Strong-QCD Regime Measurement of the Proton's Spin Structure

TL;DR

This paper reports on experimental measurements of the proton's spin structure at low Q2, providing crucial data to test and refine theoretical models of Quantum Chromodynamics in the strong force regime.

Contribution

It presents new experimental data from the g2p experiment at Jefferson Lab that serve as benchmarks for testing QCD theories at low energy scales.

Findings

Benchmark data for proton spin structure at low Q2

Test of QCD theories in the non-perturbative regime

Analysis methodology for experimental data

Abstract

The theory of the strong force, Quantum Chromodynamics (QCD) remains one of the most important ways to understand the fundamental properties of ordinary matter. However, at low momentum transfer Q2, in the regime where the strong force becomes extremely strong, our understanding of QCD for ordinary nucleons becomes hazy. Several cutting edge theories such as Chiral Perturbation Theory and Lattice QCD have provided valuable predictions in this regime, but Lattice QCD has not yet extended predictions of many important quantities to this kinematic region, and Chiral Perturbation Theory has faced several important disagreements with experimental data for the neutron over the last several decades. It is therefore of extreme importance to have a benchmark of experimental data in the low energy regime for the proton's behavior, as a test of leading theories for the behavior of QCD in this regime. The E08-027 (g2p) experiment ran at Jefferson Lab in 2012 with the goal of collecting this valuable data. Full details of the g2p experiment and my experimental work at the University of New Hampshire are presented in this thesis, as well as a detailed description of the analysis process and the exciting benchmark results, which serve as a direct test of all current and future theories of QCD in the low-Q2 regime.