Spin dependence of the heavy-quark potential: a QCD lattice analysis

Abstract We have investigated the spin dependence of the potential between heavy quarks in full lattice QCD, including the effects of light quark loops. The form of the spin-orbit, the tensor and the spin-spin forces present clear evidence for long-range scalar confinement supplemented by a Coulomb force at short distances. This agrees with observations from quarkonium spectroscopy. The QCD simulation has been carried out for Kogut-Susskind fermions with four degrees of freedom at a gauge coupling β = 5.35 and a quark mass am q = 0.01 on a 16 3 × 24 size lattice. This corresponds to a lattice spacing 0.12 fm, a spatial lattice size of about 2 fm and a light quark mass of 48 MeV.