Glueball and hybrid mass and decay with string tension below Casimir scaling

Lattice computations with excited SU(3) representations suggest that the confining gluon-gluon interaction complies with the Casimir scaling. The constituent gluon models have also assumed the Casimir scaling. Nevertheless, inspired by type-II superconductors, we explore a new scenario for the gluon gluon interaction where the adjoint string is replaced by a pair of fundamental strings, resulting in a factor of 2, smaller than the Casimir scaling factor of 9/4. To test our proposal we construct a simple constituent gluon model, extrapolated from the funnel potential for quarkonium, and apply it to compute the wavefunction of glueballs and of hybrid gluelumps. From the decay widths of quarkonium, we also extrapolate the decay widths of the glueballs. Our predictions apply to charmonia, lightonia, glueballs and hybrid gluelumps with large angular momentum J.