EUROPEAN PHYSICAL JOURNAL A, cilt.47, 2011 (SCI İndekslerine Giren Dergi)
We calculate the masses and leptonic decay constants of the heavy vector quarkonia, J/psi and gamma mesons at finite temperature. In particular, considering the thermal spectral density as well as additional operators coming up at finite temperature, the thermal QCD sum rules are acquired. Our numerical calculations demonstrate that the masses and decay constants are insensitive to the variation of temperature up to T congruent to 100MeV, however after this point, they start to fall altering the temperature. At deconfinement temperature, the decay constants attain roughly to 45% of their vacuum values, while the masses are diminished about 12%, and 2.5% for J/psi and gamma states, respectively. The obtained results at zero temperature are in good consistency with the existing experimental data as well as predictions of the other nonperturbative models.