Measuring the Neutron Spin Asymmetry A₁ⁿ in the Valence Quark Region in Hall C at Jefferson Lab

Due to the non-perturbative nature of QCD, making absolute predictions of nucleon spin structure is generally difficult. While successful lattice QCD calculations of spin and orbital angular momentum (OAM) of the quarks and gluons, integrated over their longitudinal momentum fraction (x_bj), exist, there remains much to learn about their x_bj-dependence. With the breakthrough of the quasi-PDFs formalism, confronting ab-initio calculations of unintegrated spin observables including OAM will be possible. The neutron spin asymmetry A₁ⁿ at high x_bj is a key observable for probing nucleon spin structure since in the valence domain (x_bj > 0.5) sea effects are expected to be negligible, where the total nucleon spin is considered to be carried by the valence quarks, and can enable us to study the role of quark OAM and other non-perturbative effects of the strong force. A₁ⁿ was measured in the deep inelastic scattering region of 0.30 < x < 0.75 and 3 < Q² < 10 (GeV/c)² in Hall C at Jefferson Lab using a 10.4 GeV longitudinally polarized electron beam, upgraded polarized ³He target, and the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS). The wide Q² range will explore possible Q² dependence on A₁ⁿ, provide the first precision data in the valence quark region above x_bj = 0.61, and therefore test various predictions and ultimately ab-initio lattice QCD calculations.