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Register a new userUniform description of bulk observables in the hydrokinetic model of A+A collisions at RHIC and LHC
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A simultaneous description of hadronic yields; pion, kaon, and proton spectra; elliptic flows; and femtoscopy scales in the hydrokinetic model of A+A collisions is presented at different centralities for the top BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) 2.76-TeV energies. The initial conditions are based on the Glauber Monte-Carlo simulations. When going from RHIC to LHC energy in the model, the only parameters changed are the normalization of the initial entropy defined by the number of all charged particles in most central collisions, contribution to entropy from binary collisions and baryonic chemical potential. The hydrokinetic model is used in its hybrid version (hHKM), which provides the correct match (at the isochronic hypersurface) of the decaying hadron matter evolution with hadronic ultrarelativistic quantum molecular dynamics cascade. The results are compared with the standard hybrid models where hydrodynamics and hadronic cascade are matching just at the non-space-like hypersurface of chemical freeze-out or on the isochronic hypersurface. The modification of the particle number ratios at LHC caused, in particular, by the particle annihilations at the afterburn stage is also analyzed.
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It is argued that the use of the initial Gaussian energy density profile for hydrodynamics leads to much better uniform description of the RHIC heavy-ion data than the use of the standard initial condition obtained from the Glauber model. With the modified Gaussian initial conditions we successfully reproduce the transverse-momentum spectra, v2, and the pionic HBT radii (including their azimuthal dependence). The emerging consistent picture of hadron production hints that a solution of the long standing RHIC HBT puzzle has been found.
It has long been debated whether the hydrodynamics is suitable for the smaller colliding systems such as p+p collisions. In this paper, by assuming the existence of longitudinal collective motion and long-range interactions in the hot and dense matter created in p+p collisions, the relativistic hydrodynamics incorporating with the nonextensive statistics is used to analyze the transverse momentum distributions of the particles. The investigations of present paper show that the hybrid model can give a good description of the currently available experimental data obtained in p+p collisions at RHIC and LHC energies, except for p and p^bar produced in the range of p_T> 3.0 GeV/c at sqrt(s)=200 GeV.
A further development of the evolutionary picture of A+A collisions, which we call the integrated HydroKinetic Model (iHKM), is proposed. The model comprises a generator of the initial state GLISSANDO, pre-thermal dynamics of A+A collisions leading to thermalization, subsequent relativistic viscous hydrodynamic expansion of quark-gluon and hadron medium (vHLLE), its particlization, and finally hadronic cascade ultrarelativistic QMD. We calculate mid-rapidity charged-particle multiplicities, pion, kaon, and antiproton spectra, charged-particle elliptic flows, and pion interferometry radii for Pb+Pb collisions at the energies available at the CERN Large Hadron Collider, $sqrt{s} = 2.76$ TeV, at different centralities. We find that the best description of the experimental data is reached when the initial states are attributed to the very small initial time 0.1 fm/c, the pre-thermal stage (thermalization process) lasts at least until 1 fm/c, and the shear viscosity at the hydrodynamic stage of the matter evolution has its minimal value, $eta/s = frac{1}{4pi}$. At the same time it is observed that the various momentum anisotropies of the initial states, different initial and relaxation times, as well as even a treatment of the pre-thermal stage within just viscous or ideal hydrodynamic approach, leads sometimes to worse but nevertheless similar results, if the normalization of maximal initial energy density in most central events is adjusted to reproduce the final hadron multiplicity in each scenario. This can explain a good enough data description in numerous variants of hybrid models without a prethermal stage when the initial energy densities are defined up to a common factor.
A study of energy behavior of the pion spectra and interferometry scales is carried out for the top SPS, RHIC and for LHC energies within the hydrokinetic approach. The main mechanisms that lead to the paradoxical, at first sight, dependence of the interferometry scales with an energy growth, in particular, a decrease $R_{out}/R_{side}$ ratio, are exposed. The hydrokinetic predictions for the HBT radii at LHC energies are compared with the recent results of the ALICE experiment.
Results on charged particle production in p+p, d+Au and Au+Au collisions at RHIC energies (sqrt(s_NN) = 19.6 to 200 GeV) are presented. The data exhibit remarkable, and simple, scaling behaviors, the most prominent of which are discussed.
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