Precision Measurements of $A_1^n$ in the Deep Inelastic Regime

TL;DR

This paper reports high-precision measurements of the neutron's spin asymmetry in deep inelastic scattering, providing new data that confirms previous observations and refines the understanding of quark polarization ratios.

Contribution

It presents the first high-precision neutron $A_1$ measurements over a wide kinematic range, doubling existing data and combining results with proton data to extract polarized parton distribution ratios.

Findings

Confirmed the zero crossing of $A_1^n$ near $x=0.5$

No evidence of a positive slope in $( riangle d + riangle ar{d})/(d + ar{d})$ up to $x=0.548$

Enhanced the precision of neutron spin asymmetry data in deep inelastic scattering.

Abstract

We have performed precision measurements of the double-spin virtual-photon asymmetry $A_1$ on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer. Our data cover a wide kinematic range $0.277 \leq x \leq 0.548$ at an average $Q^2$ value of 3.078~(GeV/c)$^2$, doubling the available high-precision neutron data in this $x$ range. We have combined our results with world data on proton targets to extract the ratio of polarized-to-unpolarized parton distribution functions for up quarks and for down quarks in the same kinematic range. Our data are consistent with a previous observation of an $A_1^n$ zero crossing near $x=0.5$. We find no evidence of a transition to a positive slope in $(\Delta d + \Delta \bar{d})/(d + \bar{d})$ up to $x=0.548$.