The transverse nucleon single-spin asymmetry for the semi-inclusive production of photons in lepton-nucleon scattering

TL;DR

This paper investigates the transverse single-spin asymmetry in semi-inclusive photon production during lepton-proton collisions, revealing it is driven by twist-3 quark-gluon correlations and enabling detailed probing of these matrix elements.

Contribution

It provides the first analysis of the transverse nucleon single-spin asymmetry in this process using collinear twist-3 QCD formalism at leading order.

Findings

Asymmetry generated by twist-3 quark-gluon correlations.

Allows point-by-point mapping of twist-3 matrix elements.

Highlights the process's potential for probing nucleon structure.

Abstract

We study the semi-inclusive production of real, high-$p_T$, isolated photons in unpolarized and polarized lepton-proton collisions, $\ell p\to \ell\gamma X$. In particular we analyze the transverse nucleon single-spin asymmetry within the collinear twist-3 formalism in perturbative QCD to leading order (LO) accuracy. We find that this spin asymmetry is generated by twist-3 dynamical quark-gluon-quark ($qgq$) correlations in the nucleon through the so-called soft-fermion and hard pole contributions. Hence, this process unprecedentedly allows for a point-by-point scan of the support of the dynamical $qgq$ twist-3 matrix elements $F_{FT}(x,x^\prime)$ and $G_{FT}(x,x^\prime)$ in lepton-nucleon scattering experiments.