Identified Particle Elliptic Flow Research Articles

Hadron production within a full transport approach with statistical hadronization mechanism at RHIC and LHC energies

We present for the first time results on final hadron production, with and without strangeness content, in Ultrarelativistic Heavy Ion Collisions at RHIC and LHC center of mass energies obtained combining a full 3+1D relativistic Boltzmann transport approach with a statistical hadronization mechanism. The non-perturbative interaction between quarks and gluons is described by means of a quasi-particle approach that permits to have an Equation of State close to lattice QCD. The resulting framework naturally includes both shear and bulk viscous effects. The 3+1D full transport evolution is converted to hadrons by mean of a realistic freeze-out hypersurface considering all known hadron resonances and by performing resonance decays. We present results on charged-hadron multiplicity, identified-particle spectra and identified-particle elliptic flow of π, K and p produced at RHIC and LHC energies for different centralities.

Anisotropic hydrodynamic modeling of 200 GeV Au-Au collisions

We compare phenomenological results from 3+1d quasiparticle anisotropic hydrodynamics (aHydroQP) with experimental data collected in RHIC 200 GeV Au-Au collisions. We present comparisons of identified particle spectra in different centrality clases, charged particle multiplicity versus pseudorapidity, identified particle multiplicity versus centrality across a wide range of particle species, identified particle elliptic flow versus transverse momentum, and charged particle elliptic flow as a function of transverse momentum and rapidity. We use the same aHydroQP and hadronic production/feed down codes that were used previously to describe LHC 2.76 TeV data. The aHydroQP hydrodynamic model includes the effects of both shear and bulk viscosities in addition to an infinite number of transport coefficients computed self-consistently in the relaxation time approximation. To convert to the final state hadrons, we use anisotropic Cooper-Frye freeze-out performed on a fixed-energy-density hypersurface and compute the production/feed down using a customized version of Therminator 2. We find good agreement with many heavy-ion collision observables using only smooth Glauber initial conditions parameterized by an initial central temperature of T_0 = 455 MeV, a constant shear viscosity to entropy density ratio eta/s= 0.179, and a switching (freeze-out) temperature of T_FO=130 MeV.

(3+1)D Quasiparticle Anisotropic Hydrodynamics for Ultrarelativistic Heavy-Ion Collisions.

We present the first comparisons of experimental data with phenomenological results from (3+1)D quasiparticle anisotropic hydrodynamics (aHydroQP). We compare particle spectra, average transverse momentum, and elliptic flow. The dynamical equations used for the hydrodynamic stage utilize aHydroQP, which naturally includes both shear and bulk viscous effects. The (3+1)D aHydroQP evolution obtained is self-consistently converted to hadrons using anisotropic Cooper-Frye freeze-out. Hadron production and decays are modeled using a customized version of therminator 2. In this first study, we utilized smooth Glauber-type initial conditions and a single effective freeze-out temperature T_{FO}=130 MeV with all hadronic species in full chemical equilibrium. With this rather simple setup, we find a very good description of many heavy-ion observables.

How much does the hadronic phase contribute to the observed anisotropic flow at the LHC?

Elliptic flow signals the presence of multiple interactions between the constituents of the created matter in heavy-ion collisions. This includes possible contributions from the different phases, including the hadronic phase. In these proceedings I will first show that the energy dependence of elliptic flow, based on recent ALICE and STAR beam energy scan measurements, can largely be understood in terms of a boosted thermal system. In addition, a detailed comparison between the identified particle elliptic flow measured by the ALICE collaboration and viscous hydrodynamical model calculations with and without a hadronic afterburner is performed to constrain the possible effects of individual hadron-hadron re-interaction cross-sections.

Breaking of the number-of-constituent-quark scaling for identified-particle elliptic flow as a signal of phase change in low-energy data taken at the BNL Relativistic Heavy Ion Collider (RHIC)

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 matter, which corresponds to the transition from the dominant partonic phase to the dominant hadronic phase. A multiphase transport model is used to present the dependence of NCQ scaling behavior on the different hadronization mechanisms.

Rapidity and pt dependence of identified-particle elliptic flow at RHIC

Elliptic flow has been measured by the BRAHMS experiment as a function of transverse momentum and pseudorapidity for the Au+Au reaction at GeV. Identified-particle v2(η, pt) values were obtained with the two BRAHMS spectrometers at pseudorapidities η≈ 0, 1 and 3.4. The results show that the differential v2(η, pt) values for a given particle type are essentially constant over the covered pseudorapidity range. It is suggested that the dominant cause of the observed fall-off of the integral v2 values going away from mid-rapidity is a corresponding softening of the particle spectra.

Identified Particle Spectra and Jet Interactions with the Medium

Through a combination of detector upgrades and advancements in analysis techniques, physicist at RHIC are extending their ability to identify particles at high pT . With these new capabilities some outstanding questions are being addressed: particularly regarding baryon production. Here I present an overview of new data on identified particle elliptic flow (v2), identified particle pT spectra and identified hadron-hadron correlations. The observed phenomena provide insights into hard parton interactions with the bulk matter created in heavy-ion collisions and the relevant degrees-of-freedom during its early stages.

Single inclusive spectra, Hanburg-Brown-Twiss and elliptic flow: A consistent picture at relativistic heavy-ion collider?

In these proceedings we will present the preliminary identified single inclusive particle spectra, the identified particle elliptic flow and the HBT vs. the reaction plane measured with the STAR detector at RHIC. So far none of the theoretical space-time models have been able to describe the combination of these measurements consistently. In order to see if our measurements can be understood in the context of a simple hydro-motivated blast wave model we extract the relevant parameters for this model, and show that it leads to a consistent description of these observables.