Charmonium Production with QGP and Hadron Gas Effects at SPS and FAIR

The production of charmonium in heavy-ion collisions is investigated based on Boltzmann-type transport model for charmonium evolution and langevin equation for charm quark evolution. Charmonium suppression and regeneration in both quark-gluon plasma (QGP) and hadron phase are considered. Charm quarks are far from thermalization, and regeneration of charmonium in QGP and hadron gas is neglectable at SPS and FAIR. At peripheral collisions, charmonium suppression with hadron gas explains the experimental data well. But at central collisions, additional suppression from deconfined matter (QGP) is necessary for the data. This means there should be QGP produced at central collisions, and no QGP produced at peripheral collisions at SPS energy. Predictions are also made at FAIR $\sqrt{s_{NN}}=7.7$ GeV Au+Au collisions.Comment: 6 pages, 7 figure

Theoretical Review of Charmonium Production with Different pTp_T in the Hot Medium

Charmonia with different transverse momentum $p_T$ usually comes from different mechanisms in the relativistic heavy ion collisions. This work tries to review the theoretical studies on quarkonium evolutions in the deconfined medium produced in p-Pb and Pb-Pb collisions. The charmonia with high $p_T$ are mainly from the initial hadronic collisions, and therefore sensitive to the initial energy density of the bulk medium. For those charmonia within $0.1<p_T<5$ GeV/c at the energies of Large Hadron Collisions (LHC), They are mainly produced by the recombination of charm and anti-charm quarks in the medium. In the extremely low $p_T\sim 1/R_A$ ($R_A$ is the nuclear radius), additional contribution from the coherent interactions between electromagnetic fields generated by one nucleus and the target nucleus plays a non-negligible role in the $J/\psi$ production even in semi-central Pb-Pb collisions.Comment: 6 pages, 13 figures, proceeding for CHARM 201

Strong Diffusion Effect of Charm Quarks on J/ψJ/\psi Production in Pb-Pb collisions at the LHC

We study the $J/\psi$ production based on coalescence model at $\sqrt{s_{NN}}$ = 2.76 and 5.02 TeV Pb-Pb collisions. With the colliding energy increasing from 2.76 TeV to 5.02 TeV, the number of charm pairs is enhanced by more than 50%. However, the ratio of $J/\psi$ inclusive nuclear modification factors $R^{5.02TeV}_{AA}/R^{2.76TeV}_{AA}$ is only about 1.1 $\sim$ 1.2. We find that the regeneration of $J/\psi$ is proportional to the densities of charm and anti-charm quarks, instead of their total numbers. The charm quark density is diluted by the strong expansion of quark gluon plasma, which suppresses the combination probability of heavy quarks and $J/\psi$ regeneration. This effect is more important in higher colliding energies where QGP expansion is strong. We also propose the ratio $N_{J/\psi}/(N_D)^2$ as a measurement of $c$ and $\bar c$ coalescence probability, which is only affected by the heavy quark diffusions in QGP, and does not depend on the inputs such as cold nuclear matter effects and cross sections of charm quark production. Further more, we give the predictions at the energy of Future Circular Collider ($\sqrt{s_{NN}}$ = 39 TeV)

Cold and Hot Nuclear Matter Effects on Charmonium Production in p+Pb Collisions at LHC Energy

We study cold and hot nuclear matter effects on charmonium production in p+Pb collisions at $\sqrt{s_\text{NN}}=5.02$ TeV in a transport approach. At the forward rapidity, the cold medium effect on all the $c\bar c$ states and the hot medium effect on the excited $c\bar c$ states only can explain well the $J/\psi$ and $\psi'$ yield and transverse momentum distribution measured by the ALICE collaboration, and we predict a significantly larger $\psi'$ $p_\text{T}$ broadening in comparison with $J/\psi$. However, we can not reproduce the $J/\psi$ and $\psi'$ data at the backward rapidity with reasonable cold and hot medium effects.Comment: 6 pages, 5 figure

\psi^\prime Production and B Decay in Heavy Ion Collisions at LHC

In comparison with J/\psi, the excited charmonium state \psi^\prime is loosely bounded and its yield is dominantly from the B-hadron decay. Based on the transport approach, we study the double ratio of N(\psi^\prime)/N(J/\psi) from A+A collisions to that from p+p collisions at LHC energy. We found that the primordial production in the initial stage and the regeneration in the hot medium are not significant for \psi^\prime production in heavy ion collisions at LHC and the double ratio in semi-central and central collisions is controlled by the B decay.Comment: 5 pages, 7 figure

Separating metric perturbations in near-horizon extremal Kerr spacetimes

Linear perturbation theory is a powerful toolkit for studying black hole spacetimes. However, the perturbation equations are hard to solve unless we can use separation of variables. In the Kerr spacetime, metric perturbations do not separate, but curvature perturbations do. The cost of curvature perturbations is a very complicated metric-reconstruction procedure. This procedure can be avoided using a symmetry-adapted choice of basis functions in highly symmetric spacetimes, such as near-horizon extremal Kerr. In this paper, we focus on this spacetime and (i) construct the symmetry-adapted basis functions; (ii) show their orthogonality; and (iii) show that they lead to separation of variables of the scalar, Maxwell, and metric perturbation equations. This separation turns the system of partial differential equations into one of ordinary differential equations over a compact domain, the polar angle