The bound state problem for a gauge invariant quark-antiquark system is considered in the instantaneous rest frame. Focus here is on the long range non-perturbative interaction. A two-time Green’s function is constructed for Salpeter amplitudes. The corresponding Schrödinger equation is found to be in the Salpeter form with a Wilson-loop term as the instantaneous kernel.

Short distance static quark–antiquark interaction is studied systematically using the background perturbation theory with nonperturbative background described by field correlators. A universal linear term 3Ncαsσr 2π is observed at small distance r due to the interference between perturbative and nonperturbative contributions. Possible modifications of this term due to additional subleading term...

A solution to the Schrödinger equation for the nonrelativistic Green function which is used for describing the heavy quark-antiquark pair production near the threshold in e + e − annihilation is presented. A quick comparison with existing results is given. A choice of the effective mass scale for the nonrelativistic system with Coulomb interaction is discussed.

Thermalization of quark matter and antiquark matter is studied with quarkquark-antiquark as well as quark-antiquark-antiquark elastic scatterings. Squared amplitudes of qqq̄ → qqq̄ and qq̄q̄ → qq̄q̄ at order αs are derived in perturbative QCD. Solved by a new technique, solutions of transport equations with the squared amplitudes indicate that the scatterings qqq̄ → qqq̄ and qq̄q̄ → qq̄q̄ shorten the therm...

Modifications to quark and antiquark fragmentation functions due to quark-quark (antiquark) double scattering in nuclear medium are studied systematically up to order O(αs) in deeply inelastic scattering (DIS) off nuclear targets. At the order O(αs), twist-four contributions from quark-quark (antiquark) rescattering also exhibit the Landau-Pomeranchuck-Midgal (LPM) interference feature similar ...

We compute charmonium and bottomonium decay widths in two photons or two leptons and the masses of baryons comprising two heavy quarks, solving the Salpeter equation. Baryons are considered as bound states of a quark and a diquark. The interaction energy of a quark-antiquark pair comes from the AdS/QCD correspondence.

We develop a covariant approach to describe the low–lying scalar, pseu-doscalar, vector and axialvector mesons as quark–antiquark bound states. This approach is based on an effective interaction modeling of the non– perturbative structure of the gluon propagator that enters the quark Schwinger–Dyson and meson Bethe–Salpeter equations. We consistently treat these integral equations by precisely ...

We develop a covariant approach to describe the low–lying scalar, pseu-doscalar, vector and axialvector mesons as quark–antiquark bound states. This approach is based on an effective interaction modeling of the non– perturbative structure of the gluon propagator that enters the quark Schwinger–Dyson and meson Bethe–Salpeter equations. We consistently treat these integral equations by precisely ...

Based on interaction potentials between a heavy quark and antiquark as extracted from recent QCD lattice calculations, we set up a Brueckner-type many-body scheme to study the properties of light (anti-) quarks in a quark-gluon plasma at moderate temperatures, T 1–2 Tc. The quark-antiquark T matrix, including both color-singlet and color-octet channels, and corresponding quark self-energies and...