Target normal single-spin asymmetry in inclusive electron-nucleon scattering in the 1/Nc expansion

TL;DR

This paper investigates the target normal single-spin asymmetry in inclusive electron-nucleon scattering at low energies, emphasizing two-photon exchange effects and using the 1/Nc expansion of QCD to include $ $ and $ Delta$ states.

Contribution

It introduces a systematic 1/Nc expansion approach to analyze the asymmetry, including first subleading corrections and both elastic and inelastic final states.

Findings

Asymmetry ranges from 10^{-3} to 10^{-2}.

The $ Delta$ resonance significantly influences the asymmetry.

The study provides a theoretical framework for two-photon exchange effects in low-energy scattering.

Abstract

The target normal single-spin asymmetry in inclusive electron-nucleon scattering is studied in the low-energy regime that includes the $\Delta$ resonance. The particular interest in the asymmetry resides in that it is driven by two-photon exchange effects. It probes the spin-dependent absorptive part of the two-photon exchange amplitude, which is free of infrared and collinear singularities and represents the most pristine expression of two-photon exchange dynamics. The study presented here uses the 1/Nc expansion of QCD, which combines the $N$ and $\Delta$ through the emergent SU(4) spin-flavor symmetry in the baryon sector and allows for a systematic construction of the transition EM currents. The analysis includes the first subleading corrections in the 1/Nc expansion and presents results for elastic and inelastic final states. The asymmetry is found to be in the range $10^{-3}-10^{-2}$. The $\Delta$ resonance plays an important role as an intermediate state in the elastic asymmetry and as a final state in the inclusive asymmetry.