  The decay of colour neutral 2-gluon systems in qqbar and 2q2qbar 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. Finite 2-gluon densities were
obtained with a mean square radius <r^2> of about 0.5 fm^2. These give a
significant contribution to the 2-gluon field correlators and the gluon
propagator from lattice QCD. By solving a relativistic Schroedinger equation
the binding potential of the 2-gluon density is computed. By the relation
2g->(qqbar)^n this corresponds to the confinement potential between quarks,
which is in excellent agreement with the confinement potential from lattice
QCD. The lowest bound state in this potential allows an interpretation of the
2-gluon mass as binding energy of the two gluons. The lowest glueball with
Eo=0.68+-0.10 GeV is in the mass region of the scalar sigma(550), with a mass
significantly lower then obtained in lattice QCD simulations. However, the
first and second radial excitations agree with the lattice results.
