In a model with a dynamical gluon mass, we investigate the bound states of
two and three gluons via a Schrodinger equation. The short distance potenti
al is approximated by one-gluon exchange while the long distance part is as
sumed to be of a breakable string. We estimate the masses and in particular
the sizes of low-lying bound states with no orbital angular momentum. By c
onsidering quantum-mechanical smearing of the gluon fields and normalizing
to lattice results on M-o++ and M-2++, we find that the 0(++) glueball is r
ather small in size compared with the others. The fitted gluon mass is of o
rder 600 to 700 MeV, which is reasonable. The 0(-+), 1(--), and 3(--) three
gluon glueball states are nearly degenerate, and their mass ratio with 2(+) is largely independent of all the parameters and consistent with lattice
calculations. We estimate the mass of the 1(--) glueball to be around 3.1-
3.7 GeV, which is close to the mass of J/psi and psi'.