With the adiabatic assumption in the cooling process, we discussed a new mechanism on Upsilon(1S) suppression that is due to the fast heating process at the early stage of the fireball instead of its finite decay width in finite temperature medium produced in the heavy ion collisions. We calculated the transition probability after the fast heating dissociation as a function of the temperature of the medium and the nuclear modification factor in central collisions, and found that the suppression is not negligible at RHIC, even if the width of Upsilon(1S) vanishes.
Upsilon production in heavy ion collisions at RHIC energy is investigated. While the transverse momentum spectra of the ground state Upsilon(1s) are controlled by the initial state Cronin effect, the excited $b\bar b$ states are characterized by the competition between the cold and hot nuclear matter effects and sensitive to the dissociation temperatures determined by the heavy quark potential. We emphasize that it is necessary to measure the excited heavy quark states in order to extract the early stage information in high energy nuclear collisions at RHIC.
Using a temperature-dependent potential obtained from lattice gauge calculations, we study the stability of heavy quarkonia in the quark-gluon plasma. We find that only the Upsilon(1S) and the eta_b(1S) are bound in the quark-gluon plasma, and have a small binding energy. The quark-gluon plasma may be revealed by an Upsilon(1S) dilepton peak with an invariant mass close to twice the current b quark mass, which is lower than the Upsilon(1S) mass in free space. The quarkonia Upsilon(1S) and eta_b(1S) can dissociate by collision with quarks and gluons in the quark-gluon plasma. We evaluate the di…
I discuss Upsilon production in pp collisions at RHIC, Tevatron and LHC energies, in particular the behaviour of the differential cross section in rapidity and the impact of QCD corrections on the P_T differential cross section. I also emphasise the very good agreement between the parameter-free predictions of the Colour-Singlet Model (CSM) and the first LHC data, especially in the region of low transverse momenta, which is the most relevant one for heavy-ion studies. I also show that the CSM predicts Upsilon cross-section ratios in agreement with the most recent LHC data. I then briefly discu…
We study the effect of nuclear matter in Upsilon production in dAu collisions at RHIC and pPb collisions at the LHC. We find that the nuclear modification factor, R^Upsilon_dAu, measured at RHIC is not satisfactorily reproduced by the conventional effects used in the literature, namely the modification of the gluon distribution in bound nucleons and an --effective-- survival probability for a bound state to escape the nucleus. In particular, we argue that this probability should be close to 1 as opposed to the J/psi case. We note that, at backward rapidities, the unexpected suppression of R^Up…
Properties of bottomonia (Upsilon, chi_b and Upsilon') in the Quark-Gluon Plasma (QGP) are investigated by assessing inelastic reaction rates and their interplay with open-bottom states (b-quarks or B-mesons) and color-screening. The latter leads to vanishing quarkonium binding energies at sufficiently high temperatures (close to the dissolution point), which, in particular, renders standard gluo-dissociation, g+Upsilon -> b + b-bar, inefficient due to a substantial reduction in final-state phase space. This problem is overcome by invoking a "quasifree" destruction mechanism, g,q,q-bar + Upsil…
In this paper we consider the suppression of bottomonium states in ultrarelativistic heavy ion collisions. We compute the suppression as a function of centrality, rapidity, and transverse momentum for the states Upsilon(1s), Upsilon(2s), Upsilon(3s), chi_b1, and chi_b2. Using this information, we then compute the inclusive Upsilon(1s) suppression as a function of centrality, rapidity, and transverse momentum including feed down effects. Calculations are performed for both RHIC sqrt(s_NN)=200 GeV Au-Au collisions and LHC sqrt(s_NN)=2.76 TeV Pb-Pb collisions. From the comparison of our theoretic…
We report on our recent study of Cold Nuclear Matter effects on the Upsilon production at RHIC in dAu collisions. The first experimental results available on the nuclear modification factor R_dAu have rather large uncertainties. They nevertheless allow to bring qualitative information on the nature of the nuclear effects at play on top of the usual nuclear absorption, since the latter is expected to lie in a quite small range around a value close to ten times smaller as for charmonia. At backward rapidities, the behavior of R_dAu hints at the presence of a gluon EMC effect, analogous to the qu…
We suggest that the combined effect of screening, gluon-induced dissociation, collisional damping, and reduced feed-down explains most of the sequential suppression of Y(nS) states that has been observed in PbPb relative to pp collisions at sqrt(s_NN) = 2.76 TeV. The suppression is thus a clear, albeit indirect, indication for the presence of a qgp.
Charmonium production at heavy-ion colliders is considered within the comovers interaction model. The formalism is extended by including possible secondary J/psi production through recombination and an estimate of recombination effects is made with no free parameters involved. The comovers interaction model also includes a comprehensive treatment of initial-state nuclear effects, which are discussed in the context of such high energies. With these tools, the model properly describes the centrality and the rapidity dependence of experimental data at RHIC energy, $\sqrt{s}$ = 200 GeV, for both A…
We suggest that the combined effect of screening, gluon-induced dissociation, collisional damping, and reduced feed-down explains most of the sequential suppression of Upsilon(nS) states that has been observed in PbPb relative to pp collisions at sqrt(s_NN) = 2.76 TeV. The suppression is thus a clear, albeit indirect, indication for the presence of a QGP. The Upsilon(1S) ground state suppression is essentially due to reduced feed-down, collisional damping and gluodissociation, whereas screening prevails for the suppression of the excited states.
In a recent paper [Eur. Phys. J {\bf C 44}, 567 (2005)] we developed a very general formulation to take into account explicitly the effects of hydrodynamic flow profile on the gluonic breakup of $J/ψ$'s produced in an equilibrating quark-gluon plasma. Here we apply that formulation to the case when the medium is undergoing cylindrically symmetric {\it transverse} expansion starting from RHIC or LHC initial conditions. Our algebraic and numerical estimates demonstrate that the transverse expansion causes enhancement of local gluon number density $ŋ$, affects the $\pt$-dependence of the average …
In high-energy nuclear collisions, heavy quark potential at finite temperature controls the quarkonium production. Including the relaxation of the medium induced by the relative velocity between quarkonia and the deconfined expanding matter, the Debye screening is reduced and the quarkonium dissociation takes place at a higher temperature. As a consequence of the velocity dependent dissociation temperature, the quarkonium suppression at high transverse momentum is significantly weakened in high energy nuclear collisions at RHIC and LHC.
We examine three different ways a heavy quarkonium can dissociate at temperatures below the quark-gluon plasma phase transition temperature T_c: spontaneous dissociation, dissociation by thermalization, and dissociation by collision with hadrons. We evaluate the cross sections for the dissociation of J/psi and Upsilon in collision with pion as a function of temperature, using the quark-interchange model of Barnes and Swanson. We also evaluate the dissociation temperatures for various quarkonia, and the fraction of quarkonium lying above the dissociation threshold as a function of temperature, …
We calculate transverse-momentum ($p_t$) spectra and elliptic flow of $J/ψ$'s in $Au$-$Au$ and $Cu$-$Cu$ collisions at RHIC. We employ an earlier constructed 2-component approach for direct and regenerated charmonia which is fairly consistent with the centrality dependence of inclusive $J/ψ$ yields at SPS and RHIC. Discrepancies with high-$p_t$ data in $Cu$-$Cu$ collisions are addressed by implementing effects of a finite formation time and an estimate of $B$ meson feeddown, which largely resolve the problem. The sensitivity of the spectra to the Cronin effect and different in-medium dissociat…
We revisit the standard treatment [Xu, Kharzeev, Satz and Wang, Phys. Rev. C {\bf 53}, 3051 (1996)] of $J/ψ$ suppression due to gluonic bombardment in an equilibrating quark-gluon plasma. Effects arising from gluon fugacity, relative $g-ψ$ flux, and $ψ$ meson formation time are correctly incorporated in the formulation of the gluon number density, velocity-weighted cross section, and the survival probability. Our new formulae are applied to numerically study the pattern of $J/ψ$ suppression in the central rapidity region at RHIC/LHC energies. The temperature and transverse momentum dependence …
In this talk we present a perturbative QCD improved parton model calculation for light meson production in high energy heavy ion collisions. In order to describe the experimental data properly, one needs to augment the standard pQCD model by the transverse momentum distribution of partons ("intrinsic k_T"). Proton-nucleus data indicate the presence of nuclear shadowing and multiscattering effects. Further corrections are needed in nucleus-nucleus collisions to explain the observed reduction of the cross section. We introduce the idea of proton dissociation and compare our calculations with the…
We study mutual dissociation of heavy nuclei in peripheral collisions at ultrarelativistic energies. Earlier this process was proposed for beam luminosity monitoring via simultaneous registration of forward and backward neutrons in zero degree calorimeters at Relativistic Heavy Ion Collider. Electromagnetic dissociation of heavy ions is considered in the framework of the Weizsacker-Williams method and simulated by the RELDIS code. Photoneutron cross sections measured in different experiments and calculated by the GNASH code are used as input for the calculations of dissociation cross sections.…
The present article is the follow up work of, Phys.\ Rev.\ D {\bf 94}, 094006 (2016), where we have extended the study of quarkonia dissociation in (momentum) anisotropic hot QCD medium. As evident by the experimentally observed collective flow at RHIC and LHC, the momentum anisotropy is present at almost all the stages after the collision and therefore, it is important to include its effects in the analysis. Employing the in-medium (corrected) potential while considering the anisotropy (both oblate and prolate cases) in the medium, the thermal widths and the binding energies of the heavy quar…
We suggest that gluon-induced dissociation and screening of the Y(nS) states explain the suppression of the Y(2S+3S) states relative to the Y(1S) ground state that has been observed by CMS in PbPb collisions at sqrt(s_NN)= 2.76 TeV at the CERN LHC. The minimum-bias gluodissociation cross sections of the 1S-3S states are calculated using a screened Cornell potential and a thermal gluon distribution. The 3S state dissolves due to screening before sizeable gluodissociation occurs, but for the 2S and 1S states there is an interplay between screening, gluodissociation, and feed-down from the chi_b(…
Exclusive photoproduction of heavy quarkonia in high-energy ultraperipheral ion-ion interactions (gamma A --> V A, where V = J/Psi,Upsilon and the nucleus A remains intact) offers a useful means to constrain the small-x nuclear gluon density. We discuss preliminary results on J/Psi photoproduction in Au-Au collisions at RHIC energies, as well as full simulation-reconstruction studies of photo-produced Upsilon's in Pb-Pb interactions at the LHC.
I give a brief overview of the recent theoretical progress in the study of quarkonium production in proton-nucleus collisions in view of the recent LHC and RHIC results. A special emphasis is put on the excited states such as the psi', Upsilon(2S) and Upsilon(3S).
The space-time evolution of J/psi production in central Au+Au collisions at RHIC energy is investigated in a transport model. Both gluon dissociation and continuous regeneration of J/psis inside deconfined state are considered.
We present new results on the statistical hadronization of heavy quarks at SPS, RHIC and LHC energies. Several new aspects are considered, among them a separation of the collision geometry into a ``core'' and a ``corona'' part and an estimate of the annihilation rate of charm quark in a hot plasma, together with a critical assessment of its influence on the results. For RHIC energies we investigate the centrality dependence of J/psi production focusing on the model results for different values of the charm production cross section, including its theoretical and experimental uncertainty. We als…
The effect of parton energy loss in cold nuclear matter on the suppression of quarkonia (J/psi, Upsilon) in heavy-ion collisions is investigated, by extrapolating a model based on coherent radiative energy loss recently shown to describe successfully J/psi and Upsilon suppression in proton-nucleus collisions. Model predictions in heavy-ion collisions at RHIC (Au-Au, Cu-Cu, and Cu-Au) and LHC (Pb-Pb) show a sizable suppression arising from the sole effect of energy loss in cold matter. This effect should thus be considered in order to get a reliable baseline for cold nuclear matter effects in q…
We study nuclear reactions induced by virtual photons associated with Lorentz-boosted Coulomb fields of ultrarelativistic heavy ions. Evaporation, fission and multifragmentation mechanisms are included in a new RELDIS code, which describes the deexcitation of residual nuclei formed after single and double photon absorption in peripheral heavy-ion collisions. Partial cross sections for different dissociation channels, including the multiple neutron emission ones, are calculated and compared with data when available. Rapidity and transverse momentum distributions of nucleons, nuclear fragments a…
We calculate the yields of quarkonia in heavy ion collisions at RHIC and the LHC as a function of their transverse momentum. Based upon non-relativistic quantum chromodynamics, our results include both color-singlet and color-octet contributions and feed-down effects from excited states. In reactions with ultra-relativistic nuclei, we focus on the consistent implementation of dynamically calculated nuclear matter effects, such as coherent power corrections, cold nuclear matter energy loss, and the Cronin effect in the initial state. In the final state, we consider radiative energy loss for the…
The production of charmonia is investigated for heavy-ion collisions from SPS to RHIC energies. Our approach incorporates two sources of $J/Ψ$ yield: (i) a direct contribution arising from early (hard) parton-parton collisions, subject to subsequent nuclear absorption, quark-gluon plasma and hadronic dissociation, and (ii) statistical production at the hadronization transition by coalescence of $c$ and $\bar{c}$ quarks. Within an expanding thermal fireball framework, the model reproduces $J/Ψ$ centrality dependencies observed at the SPS in Pb-Pb and S-U collisions reasonably well. The study of…
The production and space-time evolution of heavy quarks and J/psi in the quark gluon plasma is studied within the partonic transport model Boltzmann Approach to MultiParton Scatterings (BAMPS). This framework allows interactions among all partons: gluons, light quarks and heavy quarks. Heavy quarks, in particular, interact with the rest of the medium via binary scatterings with a running coupling and a more precise Debye screening which is derived from hard thermal loop calculations. We compare our results of the elliptic flow and nuclear modification factor not only to experimental data of he…
In central collisions at RHIC, the initial production of heavy quarks will for the first time yield multiple pairs of c-cbar in each central event. If a region of deconfined quarks and gluons is subsequently formed, a new mechanism for the formation of heavy quarkonium bound states will be activated. This will result from the mobility of heavy quarks in the deconfined region, such that bound states can be formed from a quark and an antiquark which were originally produced in separate incoherent interactions. Our model estimates of this effect predict a dramatic increase in the number of observ…
We calculate the absorbtion cross-sections of $B_{c}$ mesons by $π$ and $ρ$ mesons including anomalous processes using an effective hadronic Lagrangian. The enhancement of Bc production is expected due to QGP formation in heavy-ion experiments. However it is also expected that the production rate of Bc meson can be affected due to the interaction with comovers. These processes are relevant for experiments at RHIC. Thermal average cross-sections of $B_{c}$ are evaluated with form factor when a cut off parameter in it is 1 and 2 GeV. Using these thermal average cross-sections in the kinetic equa…
Heavy quark and charmonium production as well as their space-time evolution are studied in transport simulations of heavy-ion collisions at RHIC and LHC. In the partonic transport model Boltzmann Approach of MultiParton Scatterings (BAMPS) heavy quarks can be produced in initial hard parton scatterings or during the evolution of the quark-gluon plasma. Subsequently, they interact with the medium via binary scatterings with a running coupling and a more precise Debye screening which is derived from hard thermal loop calculations, participate in the flow and lose energy. We present results of th…
We update the study of the total Psi and Upsilon production cross section in proton-proton collisions at RHIC energies using the QCD-based Color-Singlet (CS) Model, including next-to-leading order partonic matrix elements. We also include charm-quark initiated processes which appear at leading order in alpha_s, but which have so far been overlooked in such studies. Contrary to earlier claims, we show that the CS yield is consistent with measurements over a broad range of J/Psi rapidities. We also find that charm-quark initiated processes, including both intrinsic and sea-like charm components,…
We review the collectivity and the suppression pattern of charmed mesons - produced in proton-nucleus and nucleus-nucleus collisions at SPS (158 AGeV) and RHIC energies (21 ATeV) - in comparison to dynamical and thermal models. In particular, we examine the charmonium `melting' and the `comover dissociation' scenarios - implemented in a microscopic transport approach - in comparison to the available data from the SPS and RHIC. The analysis shows that the dynamics of c, c-bar quarks at RHIC are dominated by partonic or `pre-hadronic' interactions in the strongly coupled plasma stage. Both the `…
Using the two-component model that includes charmonium production from initial nucleon-nucleon hard scattering and regeneration in the produced quark-gluon plasma, we study $J/ψ$ production in heavy ion collisions at 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 taken, respectively, to be twice and ten times the lower bound of $1/4π$ suggested by the Ads/CFT correspondence in the quark-gluon plasma and in the hadron gas. For the initial dissociation and the subsequent thermal decay of …
The in-medium partial decay widths of $Υ(4S) \rightarrow B\bar B$ in magnetized asymmetric nuclear matter are studied using a field theoretic model for composite hadrons with quark (and antiquark) constituents. The medium modifications of the decay widths of $Υ(4S)$ to $B\bar B$ pair in magnetized matter arise due to the mass modifications of the decaying $Υ(4S)$ as well as of the produced $B$ and $\bar B$ mesons. The in-medium masses of the open bottom meson in magnetized nuclear matter are computed from their interactions with the nucleons and the scalar mesons within a chiral effective mode…
Charmonium production and suppression in heavy-ion collisions at relativistic energies is investigated within different models, i.e. the comover absorption model, the threshold suppression model, the statistical coalescence model and the HSD transport approach. In HSD the charmonium dissociation cross sections with mesons are described by a simple phase-space parametrization including an effective coupling strength $|M_i|^2$ for the charmonium states $i=χ_c, J/ψ, ψ^\prime$. This allows to include the backward channels for charmonium reproduction by $D \bar{D}$ channels -- which are missed in t…
A variety of phenomena, which reveal itself in distant collisions of ultrarelativistic nuclei is discussed. One or both nuclei may be disintegrated in a single collision event by the long-range electromagnetic forces due to the impact of the Lorentz-boosted Coulomb fields of collision partners.The process is considered in the framework of the Weizsäcker-Williams method and simulated by the RELDIS code, which takes into account all possible channels of nuclear disintegration, including multiple neutron and proton emission and meson production. Mutual electromagnetic dissociation of nuclei in pe…
We investigate hadron production and attenuation of hadrons with strange and charm quarks (or antiquarks) as well as high transverse momentum hadrons in relativistic nucleus-nucleus collisions from 2 AGeV to 21.3 ATeV within two independent transport approaches (UrQMD and HSD). Both transport models are based on quark, diquark, string and hadronic degrees of freedom, but do not include any explicit phase transition to a quark-gluon plasma. From our dynamical calculations we find that both models do not describe the maximum in the $K^+/π^+$ ratio at 20 - 30 AGeV in central Au+Au collisions foun…
In this short review we summarize experimental information and theoretical results for the low-energy dissociation cross sections of charmonia by light hadrons. These cross sections are required for the simulation of charmonium absorption through collisions with comovers in heavy ion collisions, which competes with quark-gluon plasma production as a charmonium-suppression mechanism. If the cross sections are sufficiently large these dissociation reactions may be misinterpreted as an effect of quark-gluon plasma production. Theoretical predictions for these RHIC-related processes have used vari…
Experiments with gold-gold collisions at RHIC have revealed (i) stronger suppression of charmonium production at forward rapidity than at midrapidity and (ii) the similarity between the suppression degrees at RHIC and SPS energies. To describe these findings we employ the model that includes nuclear shadowing effects, calculated within the Glauber-Gribov theory, rapidity-dependent absorptive mechanism, caused by energy-momentum conservation, and dissociation and recombination of the charmonium due to interaction with co-moving matter. The free parameters of the model are tuned and fixed by com…
The study of photon-induced reactions in collisions of heavy nuclei at RHIC and the LHC has become an important direction of the research program of these facilities in recent years. In particular, the production of vector mesons in ultra-peripheral collisions (UPC) has been intensively studied. Owing to the intense photon fluxes, the two nuclei participating in such processes undergo electromagnetic dissociation producing neutrons at beam rapidities. Here, we introduce the $\textbf{n$\mathbf{_O^O}$n}$ (pronounced noon) Monte Carlo program, which generates events containing such neutrons. $\te…
The production of charmonia in ultrarelativistic heavy-ion collisions is investigated including two sources. These are a primordial contribution coupled with various phases of dissociation, and a statistical coalescence of $c$ and $\bar{c}$ quarks at the hadronization phase transition. Within a schematic fireball evolution, SPS data on $J/Ψ$ production can be reasonably well reproduced. Remaining discrepancies in the $Ψ'/Ψ$ ratio are discussed. Predictions for the $J/Ψ$ centrality dependence at RHIC energies are confronted with first data from PHENIX. The pertinent excitation function of the $…
We present a short review of our results on the collectivity and the suppression pattern of charmed mesons in heavy-ion collisions based on the microscopic Hadron-String Dynamics (HSD) transport approach for different scenarios of charm interactions with the surrounding matter - the 'comover' dissociation by mesons with further recreation by D+Dbar channels and 'pre-hadronic' interaction scenarios. While at SPS energies the hadronic 'comover' absorption scenario is found to be compatible with the experimental data, the dynamics of c and cbar quarks at RHIC are dominated by partonic or 'pre-had…
Quarkonium production in high-energy proton (deuteron)-nucleus collisions is investigated in the color glass condensate framework. We employ the color evaporation model assuming that the quark pair produced from dense small-x gluons in the nuclear target bounds into a quarkonium outside the target. The unintegrated gluon distribution at small Bjorken x in the nuclear target is treated with the Balitsky-Kovchegov equation with running coupling corrections. For the gluons in the proton, we examine two possible descriptions, unintegrated gluon distribution and ordinary collinear gluon distributio…
We calculate the quarkonium formation time in relativistic heavy-ion collisions from the space-time correlator of heavy quark vector currents in a hydrodynamics background with the initial nonequilibrium stage expanding only in the longitudinal direction. Using in-medium quarkonia properties determined with the heavy quark potential taken to be the free energy from lattice calculations and the fact that quarkonia can only be formed below their dissociation temperatures due to color screening, we find that $Υ$(1S), $Υ$(2S), $Υ$(3S), $J/ψ$ and $ψ^\prime$ are formed, respectively, at 1.2, 6.6, 8.…
By coupling the Boltzmann transport equations of both quarkonium and open heavy quarks, we investigate their dynamical evolution inside the quark-gluon plasma and study quarkonium production in heavy ion collisions. The Boltzmann transport equation of quarkonium is derived from the open quantum system formalism and effective field theory of QCD by assuming quarkonium interacts weakly with the plasma. The dissociation and recombination terms in the Boltzmann equation are calculated in potential nonrelativistic QCD. It is shown that the combination of quarkonium dissociation, recombination, open…
We investigate the production of psi(2S) in nuclear collisions at RHIC and LHC energies. We first address charmonium production in 200 GeV d-Au collisions at RHIC; the strong suppression of psi' mesons observed in these reactions indicates mechanisms beyond initial cold nuclear matter effects. We find that a more complete treatment of hadronic dissociation reactions leads to appreciable psi' suppression in the hadronic medium of an expanding fireball background for d-Au collisions. When implementing the updated hadronic reaction rates into a fireball for 2.76 TeV Pb-Pb collisions at LHC, the r…
We develop a set of coupled Boltzmann equations to describe the dynamical evolution of heavy quarks and quarkonia inside the quark-gluon plasma. The quarkonium dissociation and recombination terms are calculated from pNRQCD. Their interplay drives the system to a detailed balance. The heavy quark energy loss term is necessary for the system to reach kinematic thermalization. By coupling the transport equations with initial particles' momenta generated by PYTHIA and hydrodynamic medium evolutions, we can describe the $R_{AA}$ of $Υ$ family at both RHIC and LHC energies. The transverse momentum …
Applying the HSD transport approach to charmonium dynamics within the 'hadronic comover model' and the 'QGP melting scenario', we show that the suppression pattern seen at RHIC cannot be explained by the interaction with baryons, comoving mesons and/or by color screening mechanism. The interaction with hadrons in the late stages of the collision (when the energy density falls below the critical) gives a sizable contribution to the suppression. On the other hand, it does not account for the observed additional charmonium dissociation and its dependence on rapidity. Together with the failure of …
The entropic approach to dissociation of bound states immersed in strongly coupled systems is developed. In such systems, the excitations of the bound state are often delocalized and characterized by a large entropy, so that the bound state is strongly entangled with the rest of the statistical system. If this entropy $S$ increases with the separation $r$ between the constituents of the bound state, $S = S(r)$, then the resulting entropic force $F = T\ {\partial S}/{\partial r}$ ($T$ is temperature) can drive the dissociation process. As a specific example, we consider the case of heavy quarko…
The azimuthal asymmetry of $J/ψ$ suppression in non-central heavy-ion collisions is studied within a dynamic model of $J/ψ$ suppression in a deconfined partonic medium. Within this model, $J/ψ$ suppression in heavy-ion collisions is caused mainly by the initial state nuclear absorption and dissociation via gluon-$J/ψ$ scattering in deconfined partonic medium. Only the second mechanism gives arise to azimuthal asymmetry of the final $J/ψ$ production. We demonstrate that if there is an onset of suppression by quark-gluon plasma (QGP) in the NA50 data, it must be accompanied by the non-vanishing …
The production of charmonia in heavy-ion collisions is investigated within a kinetic theory framework simultaneously accounting for dissociation and regeneration processes in both quark-gluon plasma (QGP) and hadron-gas phases of the reaction. In-medium modifications of open-charm states (c-quarks, D-mesons) and the survival of J/psi mesons in the QGP are included as inferred from lattice QCD. Pertinent consequences on equilibrium charmonium abundances are evaluated and found to be especially relevant to explain the measured centrality dependence of the psi'/psi ratio at SPS. Predictions for r…
We study bottomonium production in heavy-ion collisions using a transport model which utilizes kinetic-rate and Boltzmann equations to calculate the energy, centrality and transverse-momentum ($p_T$) dependence of the yields. Both gluo-dissociation and inelastic parton-induced break-up including interference effects are improved over previous work by using in-medium binding energies from a thermodynamic $T$-matrix approach. A coalescence model with bottom-quark spectra from Langevin simulations is implemented to account for thermal off-equilibrium effects in the $p_T$-spectra of the regenerati…
The thermal suppression of heavy quark bound states represents an ideal observable for determining if one has produced a quark-gluon plasma in ultrarelativistic heavy-ion collisions. In recent years, a paradigm shift has taken place in the theory of quarkonium suppression due to new first principles calculations of the thermal widths of these states. These thermal widths are large, e.g. O(20-100 MeV) for the Upsilon(1S), and cause in-medium suppression of the states at temperatures below their traditionally defined disassociation temperatures. In order to apply the newly developed understandin…
We summarize results of recent studies of heavy quarkonia correlators and spectral functions at finite temperatures from lattice QCD and systematic T-matrix studies using QCD motivated finite-temperature potentials. We argue that heavy quarkonia dissociation shall occur in the temperature range $1.2 \le T_d/T_c \le 1.5$ by the interplay of both screening and absorption in the strongly correlated plasma medium. We discuss these effects on the quantum mechanical evolution of quarkonia states within a time-dependent harmonic oscillator model with complex oscillator strength and compare the result…
The in-medium color potential is a fundamental quantity for understanding the properties of the strongly coupled quark-gluon plasma (sQGP). Open and hidden heavy-flavor (HF) production in ultrarelativistic heavy-ion collisions (URHICs) has been found to be a sensitive probe of this potential. Here we utilize a previously developed quarkonium transport approach in combination with insights from open HF diffusion to extract the color-singlet potential from experimental results on $Υ$ production in URHICs. Starting from a parameterized trial potential, we evaluate the $Υ$ transport parameters and…
Recently a lot of progress has been made in deriving the heavy quark potential within a QCD medium. In this article we have considered heavy quarkonium in a hot quark gluon plasma phase. The heavy-quark potential has been modeled properly for short as well as long distances. The potential at long distances is modeled as a QCD string which is screened at the same scale as the Coloumb field. We have numerically solved the 1+1-dimensional Schrodinger equation for this potential and obtained the eigen wavefunction and binding energy for the $1S$ and $2S$ states of charmonium and bottomonium. Furth…
I review the origin and properties of electromagnetic fields produced in heavy ion collisions. The field strength immediately after a collision is proportional to the collision energy and reaches eB\sim(m_π)^2 at RHIC and eB\sim10 (m_π)^2 at LHC. I demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma exists as a consequence of finite electrical conductivity of the plasma. Magnetic field breaks spherical symmetry in the direction perpendicular …
