Glueball Properties at Finite Temperature in SU(3) Anisotropic Lattice QCD

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The thermal properties of the glueballs are studied using SU(3) anisotropic lattice QCD with beta=6.25, the renormalized anisotropy xi=aₛ/aₜ=4 over the lattice of the size 20³× Nₜ with Nₜ = 24, 26, 28, 30, 33, 34, 35, 36, 37, 38, 40, 43, 45, 50, 72 at the quenched level. To construct a suitable operator on the lattice, we adopt the smearing method, and consider its physical meaning in terms of the operator size. First, we construct the temporal correlators G(t) for the 0⁺⁺ and 2⁺⁺ glueballs, using more than 5,000 gauge configurations at each temperature. We then measure the pole-mass of the thermal glueballs from G(t). For the lowest 0⁺⁺ glueball, we observe a significant pole-mass reduction of about 300 MeV near Tc or mG(T≃ Tc) ≃ 0.8 mG(T 0), while its size remains almost unchanged as rho(T) ≃ 0.4fm. Finally, for completeness, as an attempt to take into account the effect of thermal width Gamma(T) at finite temperature, we perform a more general new analysis of G(t) based on its spectral representation. By adopting the Breit-Wigner form for the spectral function rho(omega), we perform the best-fit analysis as a straightforward extension to the standard pole-mass analysis. The result indicates a significant broadening of the peak as Gamma(T) 300 MeV as well as rather modest reduction of the peak center of about 100 MeV near Tc for the lowest 0⁺⁺ glueball. The temporal correlators of the color-singlet modes corresponding to these glueballs above Tc are also investigated.