The short-distance part of the low energy interaction of D-mesons and nucleons is investigated in the context of a quark model. The quark model is based on Coulomb gauge QCD. The model contains a confining Coulomb potential and a transverse hyperfine interaction consistent with a finite gluon propagator in the infrared. The basic mechanism for the short-distance interaction between the D-mesons...

Single-top-quark production probes the charged-current weak interaction of the top quark, and provides a direct measurement of the CKM matrix element Vtb. We perform two independent analyses to quantify the accuracy with which the W -gluon fusion (gq → tb̄q) and qq̄ → tb̄ signals can be extracted from the backgrounds at both the Tevatron and the LHC. Although perturbation theory breaks down at low...

We consider various special cases of gluon condensates at finite temperature. The gluon condensate for an ideal gas of gluons with a given vacuum expectation value is introduced for the sake of comparison with that calculated using the recent finite temperature lattice gauge simulations for a pure Yang-Mills SU(3) gauge theory at the known critical temperature. We extend this comparison using t...

An analysis of the baryon-baryon potential from the point of view of large-N c QCD is performed. A comparison is made between the N c-scaling behavior directly obtained from an analysis at the quark-gluon level to the N c-scaling of the potential for a generic hadronic field theory in which it arises via meson exchanges and for which the parameters of the theory are given by their canonical lar...

Three recent OPAL studies are presented in which the fragmentation process in quark and gluon jets and in identified up, down and strange flavour jets is studied. The first is a measurement is of charged particle, π, η and K multiplicities in quark and gluon jets. No evidence is found for a particle species dependent multiplicity enhancement in gluon jets. In another study leading π, K, K S , p...

The variational ansatz for the ground state wavefunctional of QCD is found to capture the anti-screening behaviour that contributes the dominant ‘−4’ to the β-function and leads to asymptotic freedom. By considering an SU(N) purely gauge theory in the Hamiltonian formalism and choosing the Coulomb gauge, the origins of all screening and anti-screening contributions in gluon processes are found ...

We construct a model for the quark-gluon vertex of Landau gauge QCD. This is of twofold interest: on the one hand the quark-gluon interaction is at the heart of quark confinement, on the other hand it is a central element in hadron phenomenology based on QCD Greens functions. We employ the non-Abelian one-loop diagram in perturbation theory, which is of order Nc. As a novelty we replace the tre...

In the early stage of ultrarelativistic heavy ion collisions both the number density and energy density of the gluons are high and a complex and highly interacting system is formed. In this paper we investigate the possibilty that a colour singlet state may be formed through the gluon-gluon (re)interaction in the system. We present our results using the Monte-Carlo simulation and discuss how th...