Gluon orbital angular momentum at small x

Abstract

We present a general analysis of the orbital angular momentum (OAM) distribution of gluons L_{g}(x) inside the nucleon with particular emphasis on the small-x region. We derive a novel operator representation of L_{g}(x) in terms of Wilson lines and argue that it is approximately proportional to the gluon helicity distribution L_{g}(x)≈-2ΔG(x) at small x. We also compute longitudinal single-spin asymmetry in exclusive diffractive dijet production in lepton-nucleon scattering in the next-to-eikonal approximation and show that the asymmetry is a direct probe of the gluon helicity/OAM distribution as well as the QCD odderon exchange.