Glueball properties at finite temperature in SU(3) anisotropic lattice QCD

Abstract

The thermal properties of the glueballs are studied using SU(3) anisotropic lattice QCD with β lat = 6.25, the renormalized anisotropy ξ ≡ as/at = 4 over the lattice of the size 20 3 × 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 for the lowest-state glueball on the lattice, we adopt the smearing method, providing an illustration of its physical meaning in terms of the operator size. First, we construct the temporal correlators G(t) for the lowest 0 ++ and 2 ++ glueballs, using more than 5,500 gauge configurations at each temperature T . We then perform the pole-mass measurement of the thermal glueballs from G(t). For the lowest 0 ++ glueball, we observe a significant pole-mass reduction of about 300 MeV in the vicinity of Tc or mG(T ≃ Tc) ≃ 0.8mG(T ∼ 0), while its size remains almost unchanged as ρ(T ) ≃ 0.4 fm. Finally, for completeness, as an attempt to take into account the effect of thermal width Γ(T ) at finite temperature, we perform a more general new analysis of G(t) based on its spectral representation. As an ansatz to the spectral function ρ(ω), we adopt the Breit-Wigner form, and perform the best-fit analysis of the temporal correlator as a straightforward extension to the standard pole-mass analysis. The result indicates a significant broadening of the peak as Γ(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.

Pentaquark baryon in anisotropic lattice QCD

“…We adopt the standard Wilson gauge action at β = 5.75 on the 12 3 × 96 lattice with the renormalized anisotropy ξ ≡ a s /a t = 4. The use of the anisotropic lattice is known to serve as a powerful tool for high-precision measurements of temporal correlators [48,49,50,51]. For quark action, we adopt O(a)-improved Wilson (clover) action with four values of the hopping parameter as κ = 0.1210(0.0010)0.1240.…”

Shear Viscosity of Yang–mills Theory in the Confinement Phase

“…In fact, it is estimated as T c = 270 MeV in the lattice gauge theory [10]. When we take this larger value, we obtain r c ∼ 2r m (T = 0).…”

“…We should notice here that the factor f (ρ) has disappeared in the final result of (23) due to the exact cancellation between the wave function and the measure in (10). As a result, F inner is independent of the temperature.…”

“…Since the lowest state of the glueball has a large mass (∼ 1.5 GeV) and its gas would not be thermodynamically active below T c ∼ 127 MeV, we expect its T-dependence to be negligible. When we adopt the critical temperature as T c ∼ 270 MeV [10], however, the cross section changes as given in (31). As a result, we expect the T-dependence of the viscosity for YM theory to be as shown in Fig.2.…”

“…When we adopt the lattice result for the glueball mass, M g ∼ 1.5 GeV, the IR cutoff is set at r m ∼ 0.4 in units where R = 1. Here we used the data in [10] since the temperature dependence of the glueball mass is given in this reference. We see that it is consistent with our analysis given in Fig.1.…”