We propose an scenario to study, from a dynamical point of view, the thermal recombination of quarks in the midsts of a relativistic heavy-ion collision. We coin the term dynamical quark recombination to refer to the process of quark-antiquark and three-quark clustering, to form mesons and baryons, respectively, as a function of energy density. Using the string-flip model we show that the probabilities to form such clusters differ. We apply these ideas to the calculation of the proton and pion spectra in a Bjorken-like scenario that incorporates the evolution of these probabilities with proper time and compute the proton to pion ratio, comparing to recent RHIC data at the highest energy. We show that for a standard choice of parameters, this ratio reaches one, though the maximum is very sensitive to the initial evolution proper time.
Within a dynamical quark recombination model we explore various proposed event-by-event observables sensitive to the microscopic structure of the QCD-matter created at RHIC energies. Charge fluctuations, charge transfer fluctuations and baryon-strangeness correlations are computed from a sample of central Au+Au events at the highest RHIC energy available ($\sqrt{s_{NN}}$=200 GeV). We find that for all explored observables, the calculations yield the values predicted for a quark-gluon plasma only at early times of the evolution, whereas the final state approaches the values expected for a hadro…
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 show that the single, non-photonic electron nuclear modification factor $R_{AA}^e$ is affected by the thermal enhancement of the heavy-baryon to heavy-meson ratio in relativistic heavy-ion collisions with respect to proton-proton collisions. We make use of the dynamical quark recombination model to compute such ratio and show that this produces a sizable suppression factor for $R_{AA}^e$ at intermediate transverse momenta. We argue that such suppression factor needs to be considered, in addition to the energy loss contribution, in calculations of $R_{AA}^e$
We evaluate the azimuthal asymmetries for the distributions of leading pions inside a jet, produced in high-energy proton-proton collisions, in kinematic configurations currently under active investigation at RHIC. Adopting a transverse momentum dependent approach, which assumes the validity of a perturbative QCD factorization scheme and takes into account all the spin and intrinsic parton motion effects, we show how the main mechanisms underlying these asymmetries, namely the Sivers and the Collins effects, can be disentangled. Furthermore, we consider the impact of color-gauge invariant init…
We study the correlation between the trigger $π$ and the associated $J/ψ$ on near and away sides in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. In the region of trigger momentum $p_t>4$ GeV/$c$, the $π$ spectrum is composed of thermal-shower and shower-shower recombinations in the frame work of the recombination model. We consider the azimuthal anisotropy in the quenched hard parton distribution and then calculate the elliptic flow parameter $v_2$ of charmed mesons ($J/ψ$, $D^0$ and $D_s$) for different centralities.
A gauge theory of pions interacting with rho-mesons at elevated temperatures is used to calculate the pressure in a hot pion gas. No reference is made to the pion's status as a QCD Goldstone boson. The role of the pion is merely that of a carrier of an SU(2) symmetry, gauged to create a vector-meson interaction, the rho playing the role of the interacting vector particle. The results are in rough agreement with much more elaborate calculations, both of the purely hadronic variety, and those that invoke quark-gluon degrees of freedom. The quark-gluon and purely hadronic calculations seemingly l…
We present a new analysis for the single-transverse spin asymmetry (SSA) for the inclusive pion and kaon productions in the proton-proton collisions measured at RHIC. The framework we use is the collinear factorization in which SSA appears as a twist-3 observable resulting from the multiparton correlations in the hadrons. As a relevant multiparton correlation, we include all the contributions associated with the quark-gluon correlation functions in the transversely polarized proton, i.e., those from the soft-gluon-pole (SGP) and the soft-fermion-pole (SFP). We have found that the SGP contribut…
Transverse spectra are calculated for various types of hadrons stemming from Au Au collisions at $\sqrt{s}=200$ GeV. We utilize a quark recombination model based on generalized Boltzmann-Gibbs thermodynamics for local hadron production at various break-up scenarios.
In order to fix the parameters for predictions of hard photon and pion production in $Au+Au$ collisions at $\sqrt{s}=200$ GeV, proton-proton and proton-nucleus data are analyzed in perturbative QCD in the energy range $\sqrt{s} \approx 20-60$ GeV and a prediction at RHIC energy is given.
We argue that the collinear factorization of the fragmentation functions in high energy hadron and nuclei collisions breaks down at transverse momenta kT < Qs/g due to high parton densities in the colliding hadrons and/or nuclei. We calculate, at next-to-leading order in projectile parton density and to all orders in target parton density, the double-inclusive cross section for production of a pair of gluons in the scalar J^(PC)=0^(++) channel. Using the low energy theorems of QCD we find the inclusive cross section for pi-meson production.
We use hydrodynamics to generate freeze-out configurations for non-central heavy-ion collisions at present and future collider energies. Such collisions are known to produce strong elliptic flow. The accompanying space-time structure of the source at freeze-out is analyzed using pion interferometry. Between RHIC and LHC energies the source deformation in the transverse plane changes sign. This leaves characteristic signatures in the emission angle dependence of the HBT radii.
By adopting a generalised parton model approach at leading order in QCD, including spin and intrinsic parton motion effects, we study the Collins azimuthal asymmetries for pions within a large-$p_T$ jet produced at mid-rapidity in polarised hadronic collisions. Using available information on the quark transversity distributions and the pion Collins functions, as extracted from semi-inclusive deeply inelastic scattering and $e^+e^-\to h_1 h_2\, X$ processes, we compute estimates for the Collins asymmetries in kinematical configurations presently investigated at RHIC by the STAR Collaboration. C…
Inclusive cross sections for pion production in $pp$ collisions are calculated for the first time fully based on unintegrated gluon, quark and antiquark distributions (uPDF). We use recently developed Kwieciński uPDF's and different phenomenological fragmentation functions (FF) from the literature. In addition to the $gg \to g$ diagram we include also $g q \to q$ and $q g \to q$ diagrams for inclusive parton production. The cross section for pions is obtained then by convoluting the inclusive parton distributions and FFs. Applications for SPS and RHIC are shown.
We discuss recent developments in assessing heavy-quark interaction in the Quark-Gluon Plasma (QGP). While induced gluon radiation is expected to be the main energy-loss mechanism for fast-moving quarks, we focus on elastic scattering which prevails toward lower energies, evaluating both perturbative (gluon-exchange) and nonperturbative (resonance formation) interactions in the QGP. The latter are treated within an effective model for D- and B-meson resonances above T_c as motivated by current QCD lattice calculations. Pertinent diffusion and drag constants, following from a Fokker-Planck equa…
We study the photoproduction of exclusive $2π^+2π^-$ mesons in ultra-peripheral heavy-ion collisions at RHIC and LHC energies. Predictions in photon-nucleus interactions are calculated for various resonances at central and forward rapidities. The recent H1 preliminary data are utilized to improve the description of the poorly known $γp \to 4π^\pm p$ process. We present the comparisons of our results to the available STAR data at RHIC, and made predictions for LHC energies.
We show that the proton and pion transverse momentum distributions measured at RHIC for all collision centralities for pions and most of the collision centralities for protons, can be simultaneously described in terms of a thermal model with common values for the radial flow and temperature, when accounting for the finite size of the interaction region at the time of decoupling. We show that this description is obtained in terms of a simple scaling law of the size of the interaction region with the number of participants in the collision. The behavior of the proton to pion ratio at mid-rapidit…
Single pion and prompt photon large transverse momentum spectra in p-p and Au-Au collisions are computed in perturbative QCD at RHIC energy, s^1/2 = 200 GeV. Next-to-leading order calculations are discussed and compared with p-p scattering data. Subsequently, quenching factors are computed to leading order for both pions and photons within the same energy loss model. The good agreement with PHENIX preliminary data allows for a lower estimate of the energy density reached in central Au-Au collisions, epsilon > 10 GeV/fm^3. Double inclusive photon-pion production in p-p and Au-Au collisions is t…
The decay of fireballs containing the disoriented chiral condensate (DCC) in A+A collisions has been analyzed. We found that the high phase-space density and probably the large final fireball volume are the favorable factors to extract a DCC signal from the thermal background. Both of these factors are expected to take place at RHIC and LHC energies. A coherent pion component then can be observed in pion spectra, in Bose-Einstein correlations and in distribution of the ratio of neutral to total pions.
Quark coalescence predictions for various multi-strange baryon to anti-baryon ratios for central Au+Au collisions at RHIC energies are compared to preliminary data of the STAR collaboration. The formation of Quark Matter and the sudden recombination of its constituent quarks into hadrons is found to be in agreement with these preliminary data. It seems that strange hadron and antihadron production in Au+Au collisions at RHIC is similar to that in Pb+Pb collisions at CERN SPS.
We analyze the transverse momentum spectra of charged pions measured in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV using the Tsallis distribution modified to include transverse flow. All the spectra are well described by the modified Tsallis distribution in an extended transverse momentum range upto 6 GeV/$c$. The kinetic freeze-out temperature ($T$), average transverse flow ($β$) and degree of non thermalization ($q$) are obtained as a function of system size for both the energies. With increasing system size $β$ shows increasing trend …
We calculate the Gaussian radius parameters of the pion-emitting source in high energy heavy ion collisions, assuming a first order phase transition from a thermalized Quark-Gluon-Plasma (QGP) to a gas of hadrons. Such a model leads to a very long-lived dissipative hadronic rescattering phase which dominates the properties of the two-pion correlation functions. The radii are found to depend only weakly on the thermalization time tau_i, the critical temperature T_c (and thus the latent heat), and the specific entropy of the QGP. The dissipative hadronic stage enforces large variations of the pi…
We discuss hadron production in heavy ion collisions at RHIC. We argue that hadrons at transverse momenta P_T < 5 GeV are formed by recombination of partons from the dense parton phase created in central collisions at RHIC. We provide a theoretical description of the recombination process for P_T > 2 GeV. Below P_T = 2 GeV our results smoothly match a purely statistical description. At high transverse momentum hadron production is well described in the language of perturbative QCD by the fragmentation of partons. We give numerical results for a variety of hadron spectra, ratios and nuclear sup…
We consider the Nuclear Modification Ratios in heavy ion collisions, R_CP and R_AA, in the region of intermediate transverse momentum, and study the dependency upon the constituent quark composition of the observed hadron. Adopting a two component recombination/fragmentation model, validated by experimental information from STAR and PHENIX, we show that a clear distinction is predicted for the f0(980) between the assumptions of $s\bar s$ or diquark-antidiquark content.
We study the single-spin (left-right) asymmetry in single-inclusive pion production in hadronic scattering. This asymmetry is power-suppressed in the transverse momentum of the produced pion and can be analyzed in terms of twist-three parton correlation functions in the proton. We present new calculations of the corresponding partonic hard-scattering functions that include the so-called "non-derivative" contributions not previously considered in the literature. We find a remarkably simple structure of the results. We also present a brief phenomenological study of the spin asymmetry, taking int…
After pointing out the difference between normal and anomalous diffusion, we consider a hadron resonance cascade (HRC) model simulation for particle emission at RHIC and point out, that rescattering in an expanding hadron resonance gas leads to a heavy tail in the source distribution. The results are compared to recent PHENIX measurements of the tail of the particle emitting source in Au+Au collisions at RHIC. In this context, we show, how can one distinguish experimentally the anomalous diffusion of hadrons from a second order QCD phase transition.
Single prompt photon and pion spectra in p-p and Au-Au collisions at intermediate RHIC energy, s^1/2 = 62.4 GeV, are computed at large transverse momentum in perturbative QCD. Next-to-leading order calculations in p-p scattering are first presented. The quenching of the prompt photon and pion yield due to energy loss processes in central Au-Au with respect to p-p collisions is then predicted. At this energy, the small phase-space available to produce hard partons makes the pion quenching almost as pronounced as at s^1/2 = 200 GeV, despite the smaller gluon density of the produced medium. In th…
We give upper bounds for transverse double-spin asymmetries in polarized proton-proton collisions by saturating the positivity constraint for the transversity densities at a low hadronic resolution scale. We consider prompt photon, jet, pion, and heavy flavor production at the BNL Relativistic Heavy Ion Collider (RHIC). Estimates of the expected statistical accuracy for such measurements are presented, taking into account the acceptance of the RHIC detectors.
The production of baryon and mesons in the RHIC heavy-ion experiments has received a lot of attention lately. Although not widely known, the pp data measured concurrently with heavy ion collisions do not find a convincing explanation in terms of simple models. We present the results of an afterburner to Pythia and Hijing event generators, simulating radial flow which seems to qualitatively explain the experimental results when applied to the pp collision data from RHIC at 200 GeV center-of-mass energy.
We compare results of $2 \to 1$ $k_t$-factorization approach with Kwieciński unintegrated parton distributions and the standard collinear factorization approach at RHIC and slightly smaller energies. Our approach contains only one free parameter responsible for internal parton motion in nucleons. In contrast to recent works in the literature our $k_t$-factorization approach includes also quark degrees of freedom in addition to purely gluonic terms. Both mid and forward rapidity regions are considered. We discuss uncertainties due to fragmentation functions. In general, the $k_t$-factorization …
We study the apparent discrepancy between the standard PQCD predictions for the meson and baryon ratios and multiplicities at moderate high $p_{T} > 2$ GeV and recent experimental measurements in $Au+Au$ collisions at $\sqrt{s}_{NN}=130$ GeV at the Relativistic Heavy Ion Collider (RHIC). We show that the differences, most pronounced in central collisions, can be explained by a strong non-perturbative baryon Junction component, which dominates the currently accessible experimental $p_{T}$ window and the non-abelian energy loss of fast partons propagating through hot and dense medium. The recent…
Different hadron transverse momentum spectra are calculated in a non-extensive statistical, quark-coalescence model. For the low-pT part a gluonic string contribution is conjectured, its length distribution and fractality are fitted to RHIC data.
We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a parton-jet nuclear modification factor at RHIC and LHC. We contrast predictions based on a linear pQCD and a highly non-linear hybrid-AdS holographic model of jet-energy loss. We find that both models require a reduction of the jet-medium coupling from RHIC to LHC to account for the measured pion nuclear modification factor. In case of the parton-jet nuclear modification factor, however, which serves as a lower bound for the LO jet nuclear modification factor of reconstructed jets, the extra…
We determine the decoupling surfaces for the hydrodynamic description of heavy ion collisions at RHIC and LHC by comparing the local hydrodynamic expansion rate with the microscopic pion-pion scattering rate. The pion $p_T$ spectra for nuclear collisions at RHIC and LHC are computed by applying the Cooper-Frye procedure on the dynamical-decoupling surfaces, and compared with those obtained from the constant-temperature freeze-out surfaces. Comparison with RHIC data shows that the system indeed decouples when the expansion rate becomes comparable with the pion scattering rate. The dynamical dec…
We present a relativistic quantum mechanical treatment of opacity and refractive effects that allows reproduction of observables measured in two-pion (HBT) interferometry and pion spectra at RHIC. The inferred emission duration is substantial. The results are consistent with the emission of pions from a system that has a restored chiral symmetry.
The production of different particle species is recently measured in $Pb-Pb$ collisions by the ALICE experiment at $\sqrt{s}=7 $TeV. This motivates the use of various bosons and baryons measured at lower center-of-mass energies in comparing their ratios to the hadron resonance (HRG) gas model and PYTHIA event generator. It is found that the particle-to-antiparticle ratios are perfectly reproduce by means of HRG and PYTHIA at RHIC and LHC energies. The kaon-to-pion and proton-to-pion ratios are entirely overestimated by the HRG model. The PYTHIA event generator obviously underestimates the kaon…
The measured data on the nuclear modification factor for pions and reconstructed jets as well as on the high-pT elliptic flow at RHIC and LHC energies are compared to results from a linear pQCD and a highly non-linear hybrid AdS holographic model of jet-energy loss. We find that the high-pT ellitic flow requires to include realistic medium transverse flow fields and a jet-medium coupling including the effects of the energy of the jet, the temperature of the bulk medium, and non-equilibrium effects close to the phase transition. We extend our jet-energy loss model that is coupled to state-of-th…
We analyze longitudinal pion spectra from \sqrt{s_{NN}}= 2 GeV to \sqrt {s_{\rm NN}}=20 GeV within Landau's hydrodynamical model and the UrQMD hybrid approach. From the measured data on the widths of the pion rapidity spectra, we extract the sound velocity c_s^2 in the dense stage of the reactions. It is found that the sound velocity has a local minimum (indicating a softest point in the equation of state, EoS) at \sqrt{s_{NN}}= 4-9 GeV, an energy range accessible at the Facility for Antiproton and Ion Research (FAIR) as well as the RHIC-Beam Energy Scan (RHIC-BES). This softening of the EoS i…
We study quark thermal recombination as a function of energy density during the evolution of a heavy-ion collision in a numerical model that reproduces aspects of QCD phenomenology. We show that starting with a set of free quarks (or quarks and antiquarks) the probability to form colorless clusters of three quarks differs from that to form colorless clusters of quark-antiquark and that the former has a sharp jump at a critical energy density whereas the latter transits smoothly from the low to the high energy density domains. We interpret this as a quantitative difference in the production of …
The hydrokinetic approach, that incorporates hydrodynamic expansion of the systems formed in A+A collisions and their dynamical decoupling, is applied to restore the initial conditions and space-time picture of the matter evolution in central Au+Au collisions at the top RHIC energy. The analysis is based on the detailed reproduction of the pion and kaon momentum spectra and femtoscopic data in whole interval of the transverse momenta studied by both STAR and PHENIX collaborations. The fitting procedure utilizes the two parameters: the maximal energy density at supposed thermalization time 1 fm…
We compare fully perturbative and fully nonperturbative pictures of high-pT energy loss calculations to the first results from LHC. While over-suppressed compared to published ALICE data, parameter-free pQCD predictions based on the WHDG energy loss model constrained to RHIC data simultaneously describe well the preliminary CMS hadron suppression, ATLAS charged hadron v2, and ALICE D meson suppression; we also provide for future reference WHDG predictions for B meson RAA. However, energy loss calculations based on AdS/CFT also qualitatively describe well the RHIC pion and non-photonic electron…
The inclusive distributions of gluons and pions are calculated with absolute normalization for high-energy nucleon-nucleon collisions. The results for several unintegrated gluon distributions from the literature are compared. The gluon distribution proposed recently by Kharzeev and Levin based on the idea of gluon saturation is tested against DIS data from HERA. We find huge differences in both rapidity and transverse momentum distributions of gluons and pions in nucleon-nucleon collisions for different models of unintegrated gluon distributions. The approximations used recently in the literat…
A soft photon approximation is used to calculate the rates of lepton pair production through virtual bremsstrahlung from both pions and quarks. Standard assumptions about the evolution of a nuclear system under collision allow pion and quark driven total production to be calculated. Comparisons are made with Dalitz decay of light mesons. These mechanisms are expected to be significant contributors to the soft dilepton mass spectra one might observe in heavy ion collisions at RHIC and LHC energies.
We calculate the one-particle hadronic spectra and correlation functions of pions based on a hydrodynamical model. Parameters in the model are so chosen that the one-particle spectra reproduce experimental results of $\sqrt{s}=130A$GeV Au+Au collisions at RHIC. Based on the numerical solution, we discuss the space-time evolution of the fluid. Two-pion correlation functions are also discussed. Our numerical solution suggests the formation of the quark-gluon plasma with large volume and low net baryon density.
We present a comprehensive analysis of photon production at RHIC and the LHC, proposing radiative hadronization as an additional photon source in high-energy heavy-ion collisions. For thermal photon, we perform relativistic viscous hydrodynamic calculation with event-by-event fluctuations.
We argue that the fireball observed at RHIC is (the analog of) a dual black hole. In previous works, we have argued that the large $s$ behaviour of the total QCD cross section is due to production of dual black holes, and that in the QCD effective field theory it corresponds to a nonlinear soliton of the pion field. Now we argue that the RHIC fireball is this soliton. We calculate the soliton (black hole) temperature, and get $T=4a <m_π>/π$, with $a$ a nonperturbative constant. For $a=1$, we get $175.76 MeV$, compared to the experimental value of the fireball ``freeze-out'' of about $176 MeV$.…
When quarks hadronize, they accelerate. Because they carry electric charge, they must radiate light as they accelerate and hadronize. This is true not only in jets but also in heavy ion collisions, where a thermalized plasma of quarks and gluons cools into a gas of hadrons. First, direct emission of photons from two quarks coalescing into pions is calculated using the quark-meson model. The yield of final-state photons to pions is found to be about $e^2/g^2_{πqq}$, which is on the order of a percent. Second, the yield of photons from the decay of highly excited color singlets, which may exist …
Suppressions of light and heavy flavor observables are considered to be excellent probes of QCD matter created in ultra-relativistic heavy ion collisions. Suppression predictions of quark and gluon jets appear to suggest a clear hierarchy according to which neutral pions should be more suppressed than D mesons, which in turn should be more suppressed than single electrons. However, joint comparison of neutral pion (light probe) and non-photonic single electron (heavy probe) suppression data at RHIC unexpectedly showed similar jet suppression for these two probes, which presents the well-known …
We investigate degree of coherence of pion sources produced in relativistic heavy ion collisions using multi-particle interferometry. In order to obtain ``true'' chaoticity, lambda^true from two-pion correlation functions measured in experiments, we make a correction for long-lived resonance decay contributions. Using this lambda^true and the weight factor which are obtained from parameter fitted to two- and three-pion correlation function, we calculate a chaotic fraction epsilon and the number of coherent sources alpha for different colliding energies. The result gives constraints on the sour…
First of all, we mention the situation of empirical analyses on 3rd order BEC (Bose-Einstein Correlation) at RHIC. Second, we introduce several theoretical formulae / approaches. Third we present our analyses of data in Au+Au at 130 GeV by STAR and preliminary data in Au+Au at 200 GeV by PHENIX Collaborations. Our results also contain analyses by means of core-halo model. Finally, we estimate that the volume of interaction in Au + Au collisions at 130 GeV is 500 fm^3, which is compared with V = R_{long} R_{out} R_{side} \sim 300 fm^3 in Pb + Pb collision at 2.76 TeV by ALICE Collaboration. Mor…
Nonperturbative effects in $D$-meson production in pion-nucleon and proton-nucleon collisions are investigated within the recombination model. The coalescence of perturbatively created charm quarks with sea- and valence-quarks from projectile and target fragments is shown to be competitive in magnitude with standard fragmentation calculations at both central (small $x_F$) and forward rapidities. Corresponding flavor asymmetries for inclusive $D$-meson production are thus mostly generated on the (light-) parton distribution level, and turn out to be in reasonable overall agreement with availabl…
The results on the main bulk observables obtained in the simulations within the integrated hydrokinetic model (iHKM) of Au+Au collisions at the RHIC energy $\sqrt{s_{NN}}=200$ GeV are presented along with the corresponding experimental data from the STAR and the PHENIX collaborations. The simulations include all the stages of the collision process: formation of the initial state, its gradual thermalization and hydrodynamization, viscous relativistic hydro-evolution, system's hadronization and particlization, and, finally, an expansion of the interacting hadron-resonance gas. The model gives a …
We present a review on the explanation of the RHIC HBT puzzle by a granular pion-emitting source of quark-gluon plasma droplets. The evolution of the droplet is described by relativistic hydrodynamics with an equation of state suggested by lattice gauge results. The granular source evolution is obtained by superposing all of the evolutions of individual droplets. Pions are assumed to be emitted thermally from the droplets at the freeze-out configuration characterized by a freeze-out temperature $T_f$. We find that the average particle emission time scales with the initial radius of the droplet…
We estimate the contributions by double-parton interactions to the cross sections for pp->pi^0 pi^0 X and dA->pi^0 pi^0 X at RHIC. We find that such contributions become important at large forward rapidities of the produced pions. This is in particular the case for dA scattering, where they strongly enhance the azimuthal-angular independent "pedestal" component of the cross section, providing a natural explanation of this feature of the RHIC dA data. We argue that the discussed processes open a window to studies of double quark distributions in nucleons. We also briefly address the roles of sh…
We calculate open heavy-flavor (HF) transport in relativistic heavy-ion collisions by applying a strong-coupling treatment in both macro- and microscopic dynamics (hydrodynamics and non-perturbative diffusion interactions). The hydrodynamic medium evolution is quantitatively constrained by bulk and multi-strange hadron spectra and elliptic flow. The heavy quark (HQ) transport coefficient is evaluated from a non-perturbative $T$-matrix approach in the Quark-Gluon Plasma (QGP) which, close to the critical temperature, leads to resonance formation and feeds into the recombination of heavy quarks …
We investigate the consequences of space-momentum correlations in quark phase-space distributions for coalescence processes at the hadronization transition. Thus far it has been proved difficult to reconcile such correlations with the empirically observed constituent quark number scaling (CQNS) at the Relativistic Heavy-Ion Collider (RHIC). To address this problem we combine our earlier developed quark recombination model with quark phase-space distributions computed from relativistic Langevin simulations in an expanding Quark-Gluon Plasma (QGP). Hadronization is based on resonance formation w…
Recently, the STAR collaboration at RHIC has presented experimental evidence for the correlation between the elliptic flow difference of charged pions and charge asymmetry as a possible signal of the chiral magnetic wave. We demonstrate that the STAR results can be understood within the standard viscous hydrodynamics.
Recent data on the azimuthal and transverse momentum dependence of high-pT>10 GeV pion nuclear modification factors in nuclear collisions at RHIC/BNL and LHC/CERN are analyzed in terms of a wide class of jet-energy loss models and a variety of transverse expanding collective flow backgrounds. RHIC data at 200 AGeV are found to be surprisingly consistent with rather different dE/dx models when coupled to recent 2+1D minimally viscous QGP flow field predictions. However, extrapolations to LHC, with parameters fixed at RHIC, favor running coupling QCD based energy-loss models over fixed coupling …
We discuss experimental features of identified particle production from nucleus-nucleus collisions. These features reflect hadronization from a deconfined partonic matter whose particle formation scheme is distinctly different from fragmentation phenomenology in elementary collisions. Multi-parton dynamics, such as quark coalescences or recombinations, appear to be essential to explain the experimental measurements at the intermediate transverse momentum of 2--5 GeV/c. Constituent quarks seem to be the dominant degrees of freedom at hadronization. Heavy quark production should help quantify de…
We present an extension of the recombination formalism to analyze the effects from the variation of the hadron wavefunctions. The hadron spectra are sensitive to the shape of the wavefunctions. However, when we fit the wavefunction parameters to the physical observables, such as the average charge radius, the final spectra are very similar each other. We discuss our numerical results in comparison with the published PHENIX and STAR data at RHIC. In the hadron spectra, the recombination of thermal partons dominates at intermediate transverse momentum ($P_{T}$ = 2 $\sim$ 5 GeV), and the fragment…
