Yunpeng Liu, Nu Xu, Pengfei Zhuang
The J/psi elliptic flow in high energy nuclear collisions is calculated in a transport model. While the flow is very small at SPS and RHIC energies, it is strongly enhanced at LHC energy due to the dominance of the regeneration mechanism.
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J/psi production and collective flow is studied with a coalescence model based on phase space distribution of charm quarks from a multi-phase transport model simulation of relativistic heavy ion collisions. Both the yield and the flow of J/psi particles are sensitive to charm quark final state interactions. As the charm quark rescattering cross section increases from 3 mb to 10 mb, J/psi elliptic flow increases faster than corresponding light hadron elliptic flows. The v_2(p_t) of J/psi crosses that of D mesons to reach a value that is about the peak value of the D meson flow but at a higher p…
Using a hadron-string cascade model, JPCIAE, we study the effect of nuclear deformation on J/Psi suppression in the collision of uranium nuclei at 200A GeV/c. We find that the J/Psi survival probability is much smaller if the major axes of both deformed nuclei are along the beam direction than if they are perpendicular to the beam direction.
We present a Glauber-based study of J/Psi and Drell-Yan yields in nucleus-nucleus collisions. Using this approach, we have investigated the impact of energy loss by the colliding nuclei on observed yields and transverse momentum spectra of J/Psi and Drell-Yan. These studies permit an assessment of the importance of initial state energy loss in relation to "anomalous" J/Psi suppression.
Using A Multi-Phase Transport (AMPT) model, we study J/psi production from interactions between charm and anti-charm quarks in initial parton phase and between D and Dbar mesons in final hadron phase of relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC). Including also the inverse reactions of J/psi absorption by gluons and light mesons, we find that the net number of J/psi from the parton and hadron phases is smaller than that expected from the superposition of initial nucleon-nucleon collisions, contrary to the J/psi enhancement predicted by the kinetic formation…
Centrality dependence of J/psi production in Au-Au collisions at 200 GeV nucleon-nucleon center of mass energy is studied using the Glauber model plus the kinetic formation model. Initial J/psi production and destruction by incoming nucleons are described by the Glauber model. J/psi-charm equilibration in the gluon plasma is described by the kinetic formation model. We explore the possibility of J/psi suppression suggested by the recent PHENIX data. We show that the J/psi yield monotonically decreases with increasing centrality in the kinetic formation model when the charm mass is smaller than…
Finite size effect on gluon dissociation of J/psi in relativistic heavy ion collisions
本文用袋模型研究纵向有限尺寸对夸克物质热力学量及J/psi胶子解离率的影响，发现解离率在特定尺寸L_m处最大，并分析了尺寸依赖的抑制行为。
Using a coherence time extracted from high precision proton-nucleus Drell-Yan measurements and a nuclear absorption cross section extracted from pA charmonium production experiments, we study J/psi production and absorption in nucleus-nucleus collisions. We find that coherence time effects are large enough to affect the measured J/psi-to-Drell-Yan ratio. The S+U data at 200A GeV/c measured by NA38 are reproduced quantitatively without the introduction of any new parameters. However, when compared with recent NA50 measurements for Pb+Pb at 158A GeV/c, the data is not reproduced in trend or in m…
The transverse momentum dependence of J/Psi suppression in relativistic heavy ion collisions is calculated from initial state gluon rescattering not only with nucleons but also with prompt gluons produced in nucleon-nucleon collisions in the early phase of the reaction. The second mechanism is new and turns out to be important in a description of the data for central collisions.
We investigate the transition from suppression to enhancement of J/psi mesons produced in ultra-relativistic nuclear collisions in the framework of the statistical hadronization model. The calculations are confronted with the most recent data from the RHIC accelerator. This comparison yields first direct evidence for generation of J/psi mesons at the phase boundary. Based on the success of this approach we make specific predictions for LHC energy.
We study the charmonium suppression in different evolutions of quark gluon plasma (QGP) based on the transport model. In the colliding energies of Large Hadron Collider, charmonium final yields are dominated by the recombination of charm and anti-charm quarks in the deconfined phase. Heavy quark diffusions depend less on the shear viscosity of the bulk medium, which makes the J/psi nuclear modification factor in the entire pT bin shows weak dependence on the shear viscosity of QGP. However, charmonium with high transverse momentum pT, can only be produced in the early stage of nuclear collisio…
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…
Using a multiphase transport model, we study the relative importance of J/psi suppression mechanisms due to plasma screening, gluon scattering, and hadron absorption in heavy ion collisions at the Relativistic Heavy Ion Collider. We find that for collisions between heavy nuclei such as Au+Au, both plasma screening and gluon scattering are important. As a result, the effect due to absorption by hadrons becomes relatively minor. The final J/psi survival probability in these collisions is only a few percent. In the case of collisions between light nuclei such as S+S, the effect of plasma screenin…
Impact of relativistic corrections to high-pT prompt-psi(2S) production at hadron colliders
研究相对论修正对强子对撞机高横动量瞬发psi(2S)产生的影响，采用碎裂函数和NRQCD计算，发现相对论修正显著增加胶子道截面，与ATLAS和CMS数据吻合良好。
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…
The suppression and collective flow of open and hidden heavy flavor in ultra-relativistic heavy ion collisions is studied with the partonic transport model Boltzmann Approach to MultiParton Scatterings (BAMPS). Charm and bottom quarks interact with the rest of the medium via elastic scatterings with an improved Debye screening and a running coupling. Heavy flavor electron data from RHIC can only be described if the cross section is multiplied with K=3.5 to mimic the contribution from radiative processes. With the same value for K we compare to elliptic flow data of D mesons at the LHC and find…
We study inclusive heavy quarkonium production with definite polarizations in polarized proton-proton collisions using the non-relativistic QCD color-octet mechanism. We present results for rapidity distributions of cross sections and spin asymmetries for the production of J/psi and psi' with specific polarizations in polarized p-p collisions at \sqrt s = 200 GeV and 500 GeV at the RHIC within the PHENIX detector acceptance range.
Combining the hydrodynamic equations for the QGP evolution and the transport equation for the primordially produced $J/ψ$ in the QGP, we investigate the $J/ψ$ transverse momentum distribution as well as its suppression in the $\sqrt{s}$=17.3A GeV Pb-Pb collisions at SPS and $\sqrt{s}$=200A GeV Au-Au collisions at RHIC. The two sets of equations are connected by the $J/ψ$ anomalous suppression induced by its inelastic scattering with gluons in the QGP. The calculated centrality dependence of $J/ψ$ suppression and average transverse momentum square agree well with the SPS data. From the comparis…
Partial contributions of elliptic v_2 and triangular v_3 flows to the hexagonal v_6 flow are studied within the HYDJET++ model for Pb+Pb collisions at sqrt{s}=2.76 TeV. Scaling of the ratio v_6^{1/6}{Psi_2} / v_2^{1/2}{Psi_2} in the elliptic flow plane, Psi_2, is predicted in the range 1 < p_T < 4 GeV/c for semicentral and semiperipheral collisions. Jets increase this ratio by about 10% and also cause its rise at p_T > 3.5 GeV/c. The part of v_6 coming from v_2 is instantly increasing as the reaction becomes more peripheral, whereas the contribution of v_3 to v_6 drops. This behavior explains …
We present baseline calculations of initial-state shadowing and final-state absorption effects on J/psi production in nucleus-nucleus collisions at the Relativistic Heavy Ion Collider. We show predictions for Au+Au and Cu+Cu collisions at \sqrt{S_{NN}}=200 GeV and Cu+Cu collisions at \sqrt{S_{NN}} = 62 GeV as a function of the rapidity, y, and the number of binary nucleon-nucleon collisions, N_{\rm coll}.
We obtain the initial phase space distribution after relativistic heavy ion collision by the CGC shattering method incorporating the uncertainty principle and solve the semi-classical Boltzmann equation which includes the gluon radiation processes. We present as a function of time the attenuation rate of high $p_T$ partons, which have transverse momenta over 6 $GeV/c$, in the medium which is formed after relativistic heavy ion collision. We calculate the elliptic flow as a function of an impact parameter, time and transverse momentum and also present the polar anisotropy, which gives the initi…
The elliptic flow in heavy ion collisions at RHIC is studied in a multiphase transport model. By converting the strings in the high energy density regions into partons, we find that the final elliptic flow is sensitive to the parton scattering cross section. To reproduce the large elliptic flow observed in Au+Au collisions at $\sqrt s=130A$ GeV requires a parton scattering cross section of about 6 mb. We also study the dependence of the elliptic flow on the particle multiplicity, transverse momentum, and particle mass.
Within the Hadron-String Dynamics (HSD) transport approach we study the suppression pattern of charmonia at RHIC with respect to centrality and rapidity employing various model concepts such as variants of the 'comover absorption' model or the 'charmonium melting' scenario. We find that especially the ratio of the forward to mid-rapidity nuclear modification factors of J/Psi (R_AA (forward) / R_AA (mid)) cannot be explained by the interactions with 'formed' comoving mesons or by the 'color screening mechanism' alone. Only when incorporating interactions of the c or c-bar quark with a pre-hadro…
The Lee-Yang zeroes method is applied to study elliptic flow ($v_2$) in Au+Au collisions at $\sqrt{s}=200A$~GeV, with the UrQMD model. In this transport approach, the true event plane is known and both the nonflow effects and event-by-event $v_2$ fluctuations exist. Although the low resolutions prohibit the application of the method for most central and peripheral collisions, the integral and differential elliptic flow from the Lee-Yang zeroes method agrees with the exact $v_2$ values very well for semi-central collisions.
I discuss the elliptic flows of $ψ(2S)$ with different production mechanisms in $\sqrt{s_{NN}}=2.76$ TeV Pb-Pb collisions. If the final $ψ(2S)$s are mainly from the recombination of uncorrelated charm and anticharm quarks at $T\approx T_c$, charm and anticharm quarks will carry large collective flows of the bulk medium, which will be inherited by the regenerated $ψ(2S)$s. This indicates a larger elliptic flow of $ψ(2S)$ than that of $J/ψ$ which can be regenerated at $T\ge T_c$, $v_2^{ψ(2S)}>v_2^{J/ψ}$. However, if the final $ψ(2S)$s are mainly from the transitions of $J/ψ\rightarrow ψ(2S)$ cau…
We predict the transverse momentum (pT) dependence of elliptic flow of thermal photons for Au+Au collisions at the Relativistic Heavy Ion Collider. We model the system hydrodynamically, assuming formation of a thermalized quark-gluon plasma at some early time, followed by cooling through expansion, hadronization and decoupling. Photons are emitted throughout the expansion history. Contrary to hadron elliptic flow, which hydrodynamics predicts to increase monotonically with pT, the elliptic flow of thermal photons is predicted to first rise and then fall again as pT increases. Photon elliptic f…
We systematically investigate the pion transverse momentum spectrum, elliptic flow, and Hanbury-Brown-Twiss (HBT) interferometry in the granular source model of quark-gluon plasma droplets in ultra-relativistic heavy ion collisions. The granular source model can well reproduce the experimental results of the Au-Au collisions at $\sqrt{s_{NN}}=$ 200 GeV and the Pb-Pb collisions at $\sqrt{s_{NN}} =$ 2.76 TeV with different centralities. We examine the parameters of the granular source models with an uniform and Woods-Saxon initial energy distributions in a droplet. The parameters exhibit certain…
We calculate the transverse momentum and invariant mass dependence of elliptic flow of thermal dileptons for Au+Au collisions at the Relativistic Heavy Ion Collider. The system is described using hydrodynamics, with the assumption of formation of a thermalized quark-gluon plasma at some early time, followed by cooling through expansion, hadronization and decoupling. Dileptons are emitted throughout the expansion history: by annihilation of quarks and anti-quarks inthe early quark-gluon plasma stage and through a set of hadronic reactions during the late hadronic stage. The resulting differenti…
Production of $c\bar c$ pairs in elementary hadron-hadron collisions is introduced in a simulation of relativistic heavy ion collisions. Coalescence of charmed quarks and antiquarks into various charmonium states is performed and the results are compared to PHENIX J$/ψ$ Au+Au data. The $χ$ and $ψ$' bound states must be included as well as the ground state J$/ψ$, given the appreciable feeding from the excited states down to the J$/ψ$ via gamma decays. Charmonium coalescence is found to take place at relatively late times: generally after $c$($\bar c$)-medium interactions have ceased. Direct pro…
We estimate the survival probability of $J/ψ$ in relativistic heavy-ion collisions, using both short-distance QCD and nuclear absorption mechanism. The suppression is found to be almost 100 percent for a thermally equilibrating quark-gluon plasma. The measurement of such a huge suppression of $J/ψ$ may suggest the existence of a deconfined partonic medium, possibly a thermalised quark-gluon plasma, at RHIC.
We study effects of eccentricity fluctuations on the elliptic flow coefficient v_2 at mid-rapidity in both Au+Au and Cu+Cu collisions at sqrt{s_NN}=200 GeV by using a hybrid model that combines ideal hydrodynamics for space-time evolution of the quark gluon plasma phase and a hadronic transport model for the hadronic matter. For initial conditions in hydrodynamic simulations, both the Glauber model and the color glass condensate model are employed to demonstrate the effect of initial eccentricity fluctuations originating from the nucleon position inside a colliding nucleus. The effect of eccen…
We argue that measurements of identified-particle elliptic flow in a wide energy range could shed light on the possible phase change in high-energy heavy ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC). When the hadronization process is dominated by quark coalescence, the number-of-constituent-quark (NCQ) scaling for the identified-particle elliptic flow can serve as a probe for studying the strong interacting partonic matter. In the upcoming RHIC low-energy runs, the NCQ scaling behavior may be broken because of the change of the effective degrees of freedom of the hot dense …
Using viscous relativistic hydrodynamics we show that systematic studies of the impact parameter dependence of the eccentricity scaled elliptic flow can distinguish between different models for the calculation of the initial source eccentricity. This removes the largest present uncertainty in the extraction of the specific viscosity of the matter created in relativistic heavy-ion collisions from precise elliptic flow measurements.
The bending of flow of identified particles from the relativistic heavy-ion collision is investigated using the iEBE-VISHNU framework. The Maxwell's equations are applied to compute the incremental drift velocity and the change in the elliptic flow of particles from the four sources of the electric force, which are of coulomb (EC), Lorentz (EL), Faraday (EF) and Plasma-based. We find out that the field evolution arouses flow at lower transverse momentum and suppresses it at higher. Heavier particles get higher initial push, and particles and their anti-particles get crudely the same elliptic f…
The implications of parton recombination processes on the dynamics of ultrarelativistic heavy-ion reactions are investigated. To do so, the quark-gluon string transport model has been extended for partonic recombination and fusion processes. Parton recombination leads to short equilibration times and improves significantly on the theoretical description of measured directed and elliptic flow, i.e., v_1 and v_2, distributions in Au+Au collisions at sqrt(s) = 200 GeV, in particular what concerns their pseudorapidity dependence. The shape of v_2(eta) is found to be closely related to fast thermal…
In high energy heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven and the Large Hadron Collider (LHC) at CERN, each central event will contain multiple pairs of heavy quarks. if a region of deconfined quarks and gluons is formed, a new mechanism for the formation of heavy quarkonium bound states will be activated. This is a result of 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. Model estimates of this effect for J/psi pro…
We employed the new issue of a parton and hadron cascade model PACIAE 2.1 to systematically investigate the charged particle elliptic flow parameter $v_2$ in the relativistic nuclear collisions at RHIC and LHC energies. With randomly sampling the transverse momentum $x$ and $y$ components of the particles generated in string fragmentation on the circumference of an ellipse instead of circle originally, the calculated charged particle $v_2(η)$ and $v_2(p_T)$ fairly reproduce the corresponding experimental data in the Au+Au/Pb+Pb collisions at $\sqrt{s_{NN}}$=0.2/2.76 TeV. In addition, the charg…
Current status of dynamical modeling of relativistic heavy ion collisions and hydrodynamic description of the quark gluon plasma is reported. We find the hadronic rescattering effect plays an important role in interpretation of mass splitting pattern in the differential elliptic flow data observed at RHIC. To demonstrate this, we predict the elliptic flow parameter for phi mesons to directly observe the flow just after hadronisation. We also discuss recent applications of outputs from hydrodynamic calculations to J/psi suppression, thermal photon radiation and heavy quark diffusion.
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 `…
A consistent picture of the Au+Au and D+Au, s^1/2 = 200 A GeV measurements at RHIC obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors including both the rapidity and transverse momentum spectra was previously developed with the simulation LUCIFER. The approach was modeled on the early production of a fluid of pre-hadrons after the completion of an initial, phase of high energy interactions. The formation of pre-hadrons is discussed here, in a perturbative QCD approach as advocated by Kopeliovich, Nemchik and Schmidt. In the second phase of LUCIFER, a considerably lower energy hadron-l…
We compute the time evolution of elliptic flow in non-central relativistic heavy-ion collisions, using a (2+1)-dimensional code with longitudinal boost-invariance to simulate viscous fluid dynamics in the causal Israel-Stewart formulation. We show that even ``minimal'' shear viscosity eta/s=hbar/(4pi) leads to a large reduction of elliptic flow compared to ideal fluid dynamics, raising questions about the interpretation of recent experimental data from the Relativistic Heavy Ion Collider.
Within a relativistic transport (ART) model for heavy-ion collisions, we show that the recently observed characteristic change from out-of-plane to in-plane elliptic flow of protons in mid-central Au+Au collisions as the incident energy increases is consistent with the calculated results using a stiff nuclear equation of state (K=380 MeV). We have also studied the elliptic flow of pions and the transverse momentum dependence of both the nucleon and pion elliptic flow in order to gain further insight about the collision dynamics.
We compute cross sections for incoherent diffractive J/Psi production in lepton-nucleus deep inelastic scattering. The cross section is proportional to A in the dilute limit and to A^(1/3) in the black disc limit, with a large nuclear suppression due to saturation effects. The t-dependence of the cross section, if it can be measured accurately enough, is sensitive to the impact parameter profile of the gluons in the nucleus and their fluctuations, a quantity that determines the initial conditions of a relativistic heavy ion collision. The nuclear suppression in incoherent diffraction shows how…
Within the framework of a multiphase transport (AMPT) model that includes both initial partonic and final hadronic interactions, we show that including mean-field potentials in the hadronic phase leads to a splitting of the elliptic flows of particles and their antiparticles, providing thus a plausible explanation of the different elliptic flows between $p$ and ${\bar p}$, $K^+$ and $K^-$, and $π^+$ and $π^-$ observed in recent Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider (RHIC).
Using a dynamical model based on the $NN \to dπ$, $NNN \to dN$, and $NNπ\to dπ$ reactions and measured proton and pion transverse momentum spectra and elliptic flows, we study the production of deuterons and their elliptic flow in heavy ion collisions at RHIC. The results are compared with those from the coalescence model. The deviation of deuteron elliptic flow from the constituent nucleon number scaling expected from the coalescence model and the comparison with the experimental data are discussed in connection to the allowed nucleon phase space in these reactions.
Estimates for elliptic flow in collisions of polarized light nuclei with spin $j\ge1$ with a heavy nucleus are presented. In such collisions the azimuthal symmetry is broken via polarization of the wave function of the light nucleus, resulting in nonzero one-body elliptic flow coefficient evaluated relative to the polarization axis. Our estimates involve experimentally well known features of light nuclei, such as their quadrupole moment and the charge radius, yielding the one-body elliptic flow coefficient in the range from 1\% for collisions with the deuteron to 5\% for for collisions with $^…
Based on the (3+1)-dimensional hydrodynamic model, the space-time evolution of hot and dense nuclear matter produced in non-central relativistic heavy-ion collisions is discussed. The elliptic flow parameter v_2 is obtained by Fourier analysis of the azimuthal distribution of pions and protons which are emitted from the freeze-out hypersurface. As a function of rapidity, the pion and proton elliptic flow parameters both have a peak at midrapidity.
We calculate the thermal photon transverse momentum spectra and elliptic flow in $\sqrt{s_{NN}} = 200$ GeV Au+Au collisions at RHIC and in $\sqrt{s_{NN}} = 2.76$ TeV Pb+Pb collisions at the LHC, using an ideal-hydrodynamical framework which is constrained by the measured hadron spectra at RHIC and LHC. The sensitivity of the results to the QCD-matter equation of state and to the photon emission rates is studied, and the photon $v_2$ is discussed in the light of the photonic $p_T$ spectrum measured by the PHENIX Collaboration. In particular, we make a prediction for the thermal photon $p_T$ spe…
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…
We study the effect of anisotropic escape mechanism on elliptic flow in relativistic heavy-ion collisions. We use Glauber model to generate initial conditions and ignore hydrodynamic expansion in the transverse direction. We employ Beer-Lambert law to allow for the transmittance of produced hadrons in the medium and calculate the anisotropy generated due to the suppression of particles traversing through the medium. In order to separate non-flow contribution due to surface bias effects, we ignore hydrodynamic expansion in the transverse direction and consider purely longitudinal boost-invarian…
Based on the framework of an extended multiphase transport model with mean-field potentials in both the partonic phase and the hadronic phase, we explain the elliptic flow difference between $π^+$ and $π^-$ in the beam-energy scan program at the relativistic heavy-ion collider by incorporating the vector-isovector potential for quarks and antiquarks with different isospins. It is found that the isospin splitting of pion elliptic flow favors a strong vector-isovector interaction, and thus serves as a probe of the quark matter equation of state as well as the QCD phase structure at finite baryon…
The hadronic transport model \textsc{art} is extended to include the production and annihilation of deuterons via the reactions $BB \leftrightarrow dM$, where $B$ and $M$ stand for baryons and mesons, respectively, as well as their elastic scattering with mesons and baryons in the hadronic matter. This new hadronic transport model is then used to study the transverse momentum spectrum and elliptic flow of deuterons in relativistic heavy ion collisions, with the initial hadron distributions after hadronization of produced quark-gluon plasma taken from a blast wave model. The results are compare…
The space-time propagation of heavy quarks in ultra-relativistic heavy ion collisions is studied within the partonic transport model Boltzmann Approach of MultiParton Scatterings (BAMPS). In this model heavy quarks interact with the partonic medium via binary scatterings. The cross sections for these interactions are calculated with leading order perturbative QCD, but feature a more precise Debye screening derived within the hard thermal loop approximation and obey the running of the coupling. Within this framework the elliptic flow and the nuclear modification factor of heavy quarks are compu…
The elliptic flows in both Cu+Cu and Au+Au collisions at the Relativistic Heavy Ion Collider are studied in a multi-phase transport model. For both collisions at same reduced impact parameter and minimum bias collisions, the elliptic flow of partons in Cu+Cu collisions is about a factor of three smaller than that in Au+Au collisions at same energy. The reduction factor is similar to the ratio of the sizes of the two colliding systems and is also related to the combined effects of initial energy density and spatial elliptic deformation in the two reactions. A similar system size dependence is a…
We use an event-by-event hydrodynamical description of the heavy-ion collision process with Glauber initial conditions to calculate the thermal emission of photons. The photon rates in the hadronic phase follow from a spectral function approach and a density expansion, while in the partonic phase they follow from the AMY perturbative rates. The calculated photon elliptic flows are lower than those reported recently by both the ALICE and PHENIX collaborations.
We analyze the second Fourier coefficient $v_2$ of the pion azimuthal distribution in non-central heavy-ion collisions in a relativistic hydrodynamic model. The exact treatment of the decay kinematics of resonances leads to almost vanishing azimuthal anisotropy of pions near the midrapidity, while the matter elliptic flow is in-plane at freeze-out. In addition, we reproduce the rapidity dependence of $v_2$ for pions measured in non-central Pb + Pb collisions at 158$A$ GeV. This suggests that resonance particles as well as stable particles constitute the in-plane flow and are important ingredie…
The quark gluon plasma produced in ultra-relativistic heavy-ion collisions exhibits remarkable features. It behaves like a nearly perfect liquid with a small shear viscosity to entropy density ratio and leads to the quenching of highly energetic particles. We show that both effects can be understood for the first time within one common framework. Employing the parton cascade Boltzmann Approach to Multi-Parton Scatterings (BAMPS), the microscopic interactions and the space-time evolution of the quark gluon plasma are calculated by solving the relativistic Boltzmann equation. Based on cross sect…
We predict a new effect due to the presence of the global vorticity in non-central relativistic heavy-ion collisions, namely a splitting of the elliptic flow parameter $v_2$ at non-zero rapidity. The size of the splitting is proposed as a new observable that can be used to constrain the initial vortical configuration of the produced QCD matter in experiments. The new findings are demonstrated by numerical calculations employing the parton cascade model, Boltzmann Approach of MultiParton Scatterings (BAMPS), for non-central Au + Au collisions at $\sqrt{s_{NN}} = 200 \ GeV$.
We calculate the elliptic flow of bottomonia produced in Pb$\,+\,$Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. We consider temperature-dependent decay widths for the anisotropic escape of various bottomonium states and observe that the transverse momentum dependence of bottomonia elliptic flow provides a tomographic information about the QGP fireball at different stages of its evolution. For the space-time evolution of the fireball, we employ simulation results from the 3+1D quasiparticle anisotropic hydrodynamic model. We find that our results for transverse momentum dependence of bottomoni…
Using the coalescence model based on nucleons from a blast-wave model with its parameters fitted to the measured proton transverse momentum spectrum and elliptic flow in heavy ion collisions at the Relativistic Heavy Ion Collider, we study the elliptic flows of light nuclei in these collisions. We find that to describe the measured elliptic flows of deuterons (anti-deuterons) and tritons (helium-3) requires that the emission source for nucleons of high transverse momentum is more elongated along the reaction plane than in the perpendicular direction. Our results thus suggest that the elliptic …
The formation and suppression dynamics of J/Psi, Chi_c and Psi-Prime mesons is studied within the HSD transport approach for Au+Au reactions at the top RHIC energy of sqrt(S)=200 GeV. Two prominent models, which have been discussed for more than a decade, are incorporated, i.e. the 'hadronic comover absorption and reformation' model as well as the 'QGP threshold' scenario, and compared to available experimental data. Our studies demonstrate that both scenarios - compatible with experimental observation at SPS energies - fail severely at RHIC energies. This combined analysis - together with the…
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