Gluon "mass" in the bag model

Bernard has proposed a measure of the effective gluon "mass" in terms of the screening of the linear potential for adjoint sources, and has extracted an estimate of $m_E=500-800\mathrm{}$ MeV from a lattice Monte Carlo calculation. The same quantity is calculated in the bag model, with the result $m_E=740\mathrm{}\pm 100$ MeV. This arises as an effect of confinement, even though the gluons themselves are massless. The model illustrates several interesting features of this measure of "mass", and these are discussed.