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

TL;DR

This study investigates the thermal behavior of glueballs in SU(3) lattice QCD, revealing a notable mass reduction and broadening of spectral peaks near the critical temperature, with implications for understanding QCD at finite temperature.

Contribution

The paper presents the first detailed lattice QCD analysis of glueball properties at finite temperature, including mass reduction and spectral broadening near T_c, using anisotropic lattices and spectral function fits.

Findings

Significant mass reduction (~300 MeV) of the 0^{++} glueball near T_c.

Broadening of the spectral peak with width ~300 MeV at T_c.

Glueball size remains nearly unchanged across the temperature range.

Abstract

The thermal properties of the glueballs are studied using SU(3) anisotropic lattice QCD with beta=6.25, the renormalized anisotropy xi=a_s/a_t=4 over the lattice of the size 20^3\times N_t with N_t = 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 T_c or m_G(T\simeq T_c) \simeq 0.8 m_G(T\sim 0), while its size remains almost unchanged as rho(T) \simeq 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) \sim 300 MeV as well as rather modest reduction of the peak center of about 100 MeV near T_c for the lowest 0^{++} glueball. The temporal correlators of the color-singlet modes corresponding to these glueballs above T_c are also investigated.