Chiral symmetry restoration with three chiral partners

Abstract

I discuss the masses of chiral partners in the context of chiral symmetry restoration at finite temperature. Using the Nambu--Jona-Lasinio model I first remind the usual situation where two mesons of opposed parity become degenerate above the chiral transition temperature. Then I consider an effective theory for D mesons where the positive parity companion presents a ``double pole structure''. In this case three different masses need to be analyzed as functions of the temperature. I suggest a possible restoration pattern at high temperatures when the back-reaction of the quark condensate is incorporated.