Evidence for Quark-Hadron Duality in the Proton Spin Asymmetry $A_1$

TL;DR

This study provides evidence that quark-hadron duality applies to the proton spin asymmetry $A_1$, showing consistency between resonance and deep-inelastic scattering measurements for $Q^2$ above 1.6 GeV$^2$.

Contribution

The paper demonstrates that the quark-hadron duality concept extends to the spin asymmetry $A_1$ in the proton, bridging resonance and deep-inelastic scattering regimes.

Findings

The average spin asymmetry in the resonance region matches deep-inelastic scattering results.

Quark degrees of freedom describe $A_1$ in the resonance region for $Q^2 > 1.6$ GeV$^2$.

Evidence supports the validity of quark-hadron duality for spin asymmetries.

Abstract

Spin-dependent lepton-nucleon scattering data have been used to investigate the validity of the concept of quark-hadron duality for the spin asymmetry $A_1$. Longitudinally polarised positrons were scattered off a longitudinally polarised hydrogen target for values of $Q^2$ between 1.2 and 12 GeV$^2$ and values of $W^2$ between 1 and 4 GeV$^2$. The average double-spin asymmetry in the nucleon resonance region is found to agree with that measured in deep-inelastic scattering at the same values of the Bjorken scaling variable $x$. This finding implies that the description of $A_1$ in terms of quark degrees of freedom is valid also in the nucleon resonance region for values of $Q^2$ above 1.6 GeV$^2$.