arXiv subjects
Publications and source records attributed to X. F. Zhang.
The mass spectra and binding radii of heavy quark bound states are studied on the basis of the reduced Bethe-Salpeter equation. The critical values of screening masses for $c\bar{c}$ and $b\bar{b}$ bound states at a finite temperature are obtained and compared with the previous results given by non-relativistic models.
Charmonium production from the hadron gas formed in ultra-relativistic heavy-ion collisions is studied. Using the $J/ψ$-hadron absorption cross section determined from the nonperturbative quark-exchange model, which has a peak value similar to that used in the comover model for $J/ψ$ suppression and a thermally averaged value consistent from that extracted from $J/ψ$ data in heavy-ion collisions, we find that $J/ψ$ production from the hadron gas is negligible in heavy-ion collisions at RHIC energies but is important at LHC energies as a result of the large number of charm mesons produced at higher energy collisions. The number of $J/ψ$ produced from these secondary collisions at LHC may be comparable to that of primary $J/ψ$'s, which are expected to be dissociated in the quark-gluon plasma created in the collisions, leading thus to a possible absence of $J/ψ$ suppression. Similar results are obtained for $ψ^\prime$ production in ultra-relativistic heavy-ion collisions.