Behavior of Charmonium Systems after Deconfinement

TL;DR

This work uses very fine isotropic lattice QCD in the quenched approximation to study charmonium in hot gluonic plasma up to $3\,T_c$. By analyzing temporal correlators and extracting spectral functions with the Maximum Entropy Method, it shows robust persistence of the $1S$ charmonia ($\eta_c$, $J/\psi$) up to about $1.5\,T_c$, while the $1P$ states ($\chi_c^0$, $\chi_c^1$) undergo strong medium modifications and likely dissolve near $T_c$, with further dissolution at higher temperatures. Spatial screening masses increase above $T_c$, suggesting dispersion relation changes in the medium. These findings contrast with some potential-model predictions and have direct implications for dilepton signatures in heavy-ion experiments, while highlighting the need for full QCD analyses to confirm the effect of dynamical quarks.

Abstract

We present a study of charmonia in hot gluonic plasma, for temperatures upto three times the deconfinement transition temperature Tc. q \bar{q} systems with quark masses close to the charm mass and different spin-parity quantum numbers were studied on very fine isotropic lattices. The analysis of temporal correlators, and spectral functions constructed from them, shows that the J/psi and eta_c survive up to quite high temperatures, with little observable change up to 1.5 Tc, and then gradually weakening and disappearing by 3 Tc. For the scalar and axial vector channels, serious modifications are induced by the hot medium already close to Tc, possibly dissociating the mesons by 1.1 Tc.

Figures (20)

• Figure 1: Spectral functions at 0.9 $T_c$ for the different channels, for set III.
• Figure 2: Spectral functions at 0.75 $T_c$ for the different channels, for set II.
• Figure 3: Spectral functions for different channels at $0.6T_c$ for set IB.
• Figure 4: Spectral functions for the vector channel below $T_c$, using both the free spectral function and the high energy part of the spectral function from interacting theory as default model. Set IB.
• Figure 5: Ratio of the measured correlators at 0.9 $T_c$ with the reconstructed correlators at this temperature, using the spectral function at 0.6 $T_c$ (see text), for different channels and set IB. For visual clarity, the vector and scalar channels have been shifted horizontally.