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

The target normal single-spin asymmetry in inclusive electron-nucleon scattering is studied in the lowenergy 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/N, 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 electromagnetic (EM) currents. The analysis includes the first subleading corrections in the 1/N, 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.