Abstract
We study the semi-inclusive production of real, high-pT, isolated photons in unpolarized and polarized lepton-proton collisions, ℓp→ℓγX. 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 FFT(x,x′) and GFT(x,x′) in lepton-nucleon scattering experiments.