Short-range potentials from QCD at order g2

We systematically compute the effective short-range potentials arising from second-order QCD diagrams related to bound states of quarks, antiquarks and gluons. Our formalism relies on the assumption that the exchanged gluons are massless, while the constituent gluons as well as the lightest quarks acquire a nonvanishing constituent mass because of confinement. We recover the well-known Fermi-Breit interaction in the heavy quark limit. Such an effective potential has been proved in the past to be relevant for the building of accurate potential models describing usual hadrons (mesons and baryons). The general potentials we obtain in this work are also expected to be useful in the understanding of exotic hadrons such as glueballs and qbar q g hybrids. In particular, we compute for the first time an effective short-range quark-gluon potential, and show the existence of a quadrupolar interaction term in this case. We also discuss the influence of a possible nonzero mass for the exchanged gluons.