Single-spin asymmetry from pomeron-odderon interference
  The transverse single-spin asymmetry A_N observed in high energy proton-proton collisions p^\uparrow p \to pi X has been found to increase with the momentum fraction x_F of the pion up to the largest measured x_F \sim 0.8, where A_N \simeq 40%. We consider the possibility that the asymmetry is due to a non-perturbatively generated spin-flip coupling in soft rescattering on the target proton. We demonstrate using perturbation theory that a non-vanishing asymmetry can be generated through interference between exchanges of even and odd charge conjugation provided both helicity flip and non-flip couplings contribute. Pomeron and odderon exchange can thus explain the energy independence of the asymmetry and predicts that the asymmetry should persist in events with large rapidity gaps. 
M. Jarvinen