Survival of charmonia above Tc in anisotropic lattice QCD

Abstract

We find a strong evidence for the survival of $J/\Psi$ and ${\eta }_c$ as spatially-localized $c\bar{c}$ (quasi-)bound states above the QCD critical temperature $T_c$, by investigating the boundary-condition dependence of their energies and spectral functions. In a finite-volume box, there arises a boundary-condition dependence for spatially spread states, while no such dependence appears for spatially compact states. In lattice QCD, we find almost {\it no} spatial boundary-condition dependence for the energy of the $c\bar{c}$ system in $J/\Psi$ and ${\eta }_c$ channels for $T\simeq (1.11-2.07)T_c$. We also investigate the spectral function of charmonia above $T_c$ in lattice QCD using the maximum entropy method (MEM) in terms of the boundary-condition dependence. There is {\it no} spatial boundary-condition dependence for the low-lying peaks corresponding to $J/\Psi$ and ${\eta }_c$ around 3GeV at $1.62T_c$. These facts indicate the survival of $J/\Psi$ and ${\eta }_c$ as compact $c\bar{c}$ (quasi-)bound states for $T_c<T<2T_c$.

4 pages, 1 figure