Quark-bag vibrations in heavy quark systems

Mulders et al. examined the consequences of bag vibrations in heavy quark systems and determined the upper bound on the inertia mass of the bag to be ~0.2 GeV by requiring the bag vibrational levels to remain above the observed four s-state levels in the upsilonium spectrum. We reexamine Mulders et al.'s model by taking full account of nonadiabatic effects which they ignored, and we essentially confirm their results. Implications of the upper bound of the inertia mass on the spectra of light quark systems are discussed.