GLUEBALL-LIKE SCREENING MASSES IN PURE SU(3) AT FINITE TEMPERATURES

We investigate the finite-temperature excitation spectrum in the gluon sector of SU(3) pure gauge theory through measurements of screening m asses in correlations of loop operators. We develop the classification of such operators under the symmetry group of the ''z-slice''. In the confined phase of the theory, we find that the spectrum dynamically r ealises the zero-temperature symmetries. We observe a large thermal sh ift of the 0++ glueball mass. In the deconfined phase, the spectrum di stinguishes between operators coupling to electrically and magneticall y polarised gluon fields. The former yields a screening mass equal to the Wilson-line screening mass; the latter a method for the measuremen t of the magnetic mass in the high-temperature limit.