ROMANIAN JOURNAL OF PHYSICS, cilt.59, ss.140-154, 2014 (SCI İndekslerine Giren Dergi)
Using the additional operators coming up at finite temperature, we calculate the masses and decay constants of the P wave heavy axial-vector chi(b1) and chi(c1) quarkonia in the framework of thermal QCD sum rules. In the calculations, we take into account the perturbative two loop order alpha(s) corrections and nonperturbative effects up to the dimension four condensates. It is observed that the masses and decay constants almost remain unchanged with respect to the variation of the temperature up to T similar or equal to 100 MeV, however after this point, the decay constants decrease sharply and approach approximately to zero at critical temperature. The decreasing in values of the masses is also considerable after T similar or equal to 100 MeV.