Multi-Gluon Field Approach of QCD

The decay of 2-gluon colour singlets in quarks: 2g → qq(bar) + 2q 2q(bar) has been simulated with the Monte-Carlo method, taking into account an effective 1-gluon exchange interaction between the emitted quarks, which was folded with a 2-gluon density determined self-consistently. 2-gluon densities were found with different radii, which correspond to 0++ glueballs of the size of light qq(bar), ss(bar), cc(bar), bb(bar) and heavier qq(bar) systems. Binding potentials between the two gluons have been deduced, which are consistent with the confinement potential from lattice results. However, self-consistency for the deduction of 2-gluon densities requires massless (or very light) quarks for all flavours. The masses are given by the binding energies of quarks and gluons, yielding excitation spectra of 0++ glueballs and Φ, J/ψ and Υ states consistent with observation. The sum of q-q potentials yields a strong coupling αs consistent with the available data up to large momenta. The nucleon is described by a gluonium state coupled to 3 valence quarks, yielding ground state and radial excitations consistent with experiment. Finally, we discuss the compressibility of the nucleon and relate it to that of nuclear matter. (author)