Where does the Rho Go? Chirally Symmetric Vector Mesons in the Quark--Gluon Plasma.

If the phase transition of $QCD$ at nonzero temperature is dominated by the (approximate) restoration of chiral symmetry, then the transition might be characterized using a gauged linear sigma model. Assuming that vector meson dominance holds, such sigma models predict that at the temperature of chiral restoration, the pole mass of the thermal $\rho$ meson is greater than that at zero temperature; in the chiral limit and in weak coupling this mass is $\sim 962 \, MeV$. The width of the thermal $\rho-a_1$ peak is estimated to be about $200 - 250 \, MeV$.