Resonant contributions to polarized proton structure functions

TL;DR

This paper calculates the contributions of nucleon resonances to polarized proton structure functions using experimental electroexcitation data, confirming their significant role and examining quark-hadron duality in the resonance region.

Contribution

It provides the first detailed computation of resonance contributions to polarized structure functions using CLAS data, including interference effects, and assesses quark-hadron duality.

Findings

Resonance contributions account for observed structure in $g_1$ and $g_2$.

Resonances significantly influence the behavior of polarized structure functions.

Quark-hadron duality holds to a certain degree in the resonance region.

Abstract

Nucleon resonance contributions to the polarized proton $g_1$ and $g_2$ structure functions are computed from resonance electroexcitation amplitudes extracted from CLAS exclusive meson electroproduction data. Including resonances in the mass range up to 1.75 GeV, and taking into account the interference between excited states, we compare the resonant contributions with the polarized proton structure function and polarization asymmetry data from Jefferson Lab 6 GeV measurements. All resonance-like structure observed in the polarized structure functions and asymmetries can be attributed to the resonant contributions, confirming their essential role in the behavior of $g_1$ and $g_2$ in the resonant region over the entire range $Q^2 < 7.5$ GeV$^2$ covered by the measurements. Comparing the resonance contributions with the $g_1$ and $g_2$ structure functions computed from parton distribution functions extrapolated from the deep-inelastic region, we also quantify the degree to which quark-hadron duality holds for $g_1$ and $g_2$ and their moments.