Improved Hilbert moment thermal QCD sum rules for Bs meson and stability with respect to moment parameter

In this paper, we deal with the temperature dependence of the leptonic decay constant and mass of Bs meson in the framework of the Hilbert moment QCD sum rule. In our calculations, we improve the thermal QCD sum rules, taking into account the thermal spectral density and the perturbative 2-loop order corrections to the correlation function. Moreover, we investigate the stability of the results with respect to the Hilbert moment parameter. Our numerical calculations demonstrate that the mass and decay constant are insensitive to the variation of temperature up to T approximately equal to 100 MeV; however, after this value, they start to decrease with increasing temperature. We observe that the results are stable for different values of the Hilbert moment parameter, n. At deconfinement or critical temperature, the decay constant and mass approach to roughly 16% and 78% of their values at zero temperature, respectively. The obtained results at zero temperature are in good agreement with the existing experimental data as well as predictions of the other nonperturbative models.