Charmonium production in relativistic heavy-ion collisions

Abstract

Using the two-component model that includes charmonium production from both initial nucleonnucleon hard scattering and regeneration in the produced quark-gluon plasma, we study J/ψ production in heavy-ion collisions at the SPS, RHIC and LHC. For the expansion dynamics of produced hot dense matter, we use a schematic viscous hydrodynamic model with the specific shear viscosity in the quark-gluon plasma and the hadronic matter taken, respectively, to be twice and ten times the lower bound of 1/4π suggested by the AdS/CFT correspondence. For the initial dissociation and the subsequent thermal decay of charmonia in the hot dense matter, we use the screened Cornell potential to describe the properties of charmonia and perturbative QCD to calculate their dissociation cross sections. Including regeneration of charmonia in the quark-gluon plasma via a kinetic equation with in-medium chamonium decay widths, we obtain a good description of measured J/ψ nuclear modification factors in Pb+Pb collisions at √ sNN = 1.73 GeV at SPS and in Au+Au collisions at √ sNN = 200 GeV at RHIC. A reasonable description of the measured nuclear modification factor of high transverse momenta J/ψ in Pb+Pb collisions at √ sNN = 2.76 TeV at LHC is also obtained.

High-temperature superconductivity in one-unit-cell FeSe films

“…The FeSe/STO interface enhancement of the superconducting gap decays exponentially with a characteristic length of 2.4 UC as film thickness increases [43], which matches well with the decay behavior of the penetrating field intensity of Fuchs-Kliewer phonon modes in STO ( figure 17(b)) [121]. However, there is almost no such interface effect between FeSe and graphene [43,61,62]. These results point to interfacial electron-phonon coupling as the likely origin of the high-T c superconductivity in 1-UC FeSe/STO system.…”

“…FeSe/STO system exhibits unique superconducting property, i.e. onset T c decreases with increasing film thickness (figure 8(a) and 8(b)) [82], which is opposite to that observed in traditional superconducting films, including FeSe films grown on graphene [61]. Besides, proper annealing process is crucial to the observation of superconductivity in FeSe/STO system.…”

“…The realization of high-T c topological superconductors would significantly promote the development of topological quantum computation in future. Table 1 Reprinted from [61]. Differential tunneling conductance (dI/dV) spectra taken along the arrows shown in (a-e).…”

“…Superconducting FeSe crystalline thin films can be prepared by layer-by-layer epitaxial growth on double-layer graphene along (001) crystal direction (figure 1) [61,62]. Graphene substrates are acquired by heat-treatment of SiC (0001) substrate to evaporate silicon atoms at surface [63,64].…”

Gluon dissociation ofJ/ψbeyond the dipole approximation

“…With experimental data from heavy-ion collisions at various energies [2][3][4][5][6][7] available from the Super Proton Synchrotron, the Relativistic Heavy Ion Collider, and the Large Hadron Collider, there have been extensive theoretical studies to understand the observed results [1,[8][9][10][11][12][13][14][15][16]. Some of these studies were based on the effect of color screening [1] or the assumption of statistical production of J /ψ during hadronization of the QGP [17].…”