Charmonium properties in deconfinement phase in anisotropic lattice QCD

J/Psi and eta(c) above the QCD critical temperature T-c are studied in anisotropic quenched lattice QCD, considering whether the c (c) over bar systems above T-c are spatially compact (quasi-)bound states or scattering states. We adopt the standard Wilson gauge action and O(a)-improved Wilson quark action with renormalized anisotropy a(s)/a(t)=4.0 at beta=6.10 on 16(3)x(14-26) lattices, which correspond to the spatial lattice volume V equivalent to L-3 similar or equal to(1.55 fm)(3) and temperatures T similar or equal to(1.11-2.07)T-c. We investigate the c (c) over bar system above T-c from the temporal correlators with spatially extended operators, where the overlap with the ground state is enhanced. To clarify whether compact charmonia survive in the deconfinement phase, we investigate spatial boundary-condition dependence of the energy of c (c) over bar systems above T-c. In fact, for low-lying S-wave c (c) over bar scattering states, it is expected that there appears a significant energy difference Delta E equivalent to E(APBC) -E(PBC) similar or equal to 2 root m(c)(2)+3 pi(2)/L-2 - 2m(c) (m(c): charm quark mass) between periodic and antiperiodic boundary conditions on the finite-volume lattice. In contrast, for compact charmonia, there is no significant energy difference between periodic and antiperiodic boundary conditions. As a lattice QCD result, almost no spatial boundary-condition dependence is observed for the energy of the c (c) over bar system in J/Psi and eta(c) channels for T similar or equal to(1.11-2.07)T-c. This fact indicates that J/Psi and eta(c) would survive as spatially compact c (c) over bar (quasi-)bound states below 2T(c). We also investigate a P-wave channel at high temperature with maximal entropy method and find no low-lying peak structure corresponding to chi(c1) at 1.62T(c).