Scalar quarkonia at finite temperature

Abstract

Masses and decay constants of the scalar quarkonia, ${\ensuremath{\chi}}_{Q0}(Q=b,c)$ with quantum numbers ${I}^{G}({J}^{PC})={0}^{+}({0}^{++})$, are calculated in the framework of the QCD sum rules approach both in vacuum and finite temperature. The masses and decay constants remain unchanged up to $T\ensuremath{\simeq}100\text{ }\text{ }\mathrm{MeV}$ but they start to diminish with increasing the temperature after this point. Near the critical or deconfinement temperature, the decay constants reach approximately to 25% of their values in vacuum, while the masses are decreased about 6% and 23% for bottom and charm cases, respectively. The results at zero temperature are consistent with the existing experimental values and predictions of the other nonperturbative approaches. Our predictions on the decay constants in vacuum, as well as the behavior of the masses and decay constants with respect to the temperature, can be checked in the future experiments.