Are We Close to an Equilibrated Quark-Gluon Plasma? Nonequilibrium Analysis of Particle Production in Ultrarelativistic Heavy Ion Collisions

Bass, Steffen A.; Belkacem, M.; Brandstetter, M.; Bleicher, Marcus; Gerland, L.; Konopka, J.; Neise, L.; Spieles, C.; Soff, S.; Weber, H. J.; Stöcker, H.; Greiner, Walter

doi:10.1103/physrevlett.81.4092

Cited by 35 publications

(28 citation statements)

References 45 publications

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“…However, one would expect a fairly large chi-squared for the single source statistical model fit in case of a continuous decoupling scenario, which is not observed in the data. It should also be noted that the use of 4π integrated yields at SPS energies creates ambiguities in the fit, since many hadron ratios have been shown to exhibit a strong rapidity dependence at SPS (and lower) beam energies [32,33]. True progress on this issue can only be achieved if a model-independent method is found to determine the chemical decoupling time of individual hadron species.…”

Section: Hadron Yields and Ratiosmentioning

confidence: 99%

SQM 2006: theory summary and perspectives

Bass¹

2006

J. Phys. G: Nucl. Part. Phys.

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Section: Hadron Yields and Ratiosmentioning

confidence: 99%

SQM 2006: theory summary and perspectives

Bass¹

2006

J. Phys. G: Nucl. Part. Phys.

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“…This includes detailed studies of thermalization [18], particle abundancies and spectra [19], strangeness production [20], photonic and leptonic probes [21] , J/Ψ's [22] and event-byevent fluctuations [23].…”

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confidence: 99%

Global observables and secondary interactions in central Au+Au reactions ats=200AGeV

et al. 2000

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The Ultra-relativistic Quantum Molecular Dynamics model (UrQMD) is used to study global observables in central reactions of Au+Au at √ s = 200 AGeV (RHIC). Strong stopping governed by massive particle production is predicted if secondary interactions are taken into account. The underlying string dynamics and the early hadronic decoupling implies only small transverse expansion rates. However, rescattering with mesons is found to act as a source of pressure leading to additional flow of baryons and kaons, while cooling down pions. LBNL-preprint: LBNL-44599ξ Feodor Lynen Fellow of the Alexander v. Humboldt Foundation * E-mail: bleicher@nta2.lbl.gov 1 One of the major goals of the relativistic heavy ion collider (RHIC) at Brookhaven National Laboratory is to explore the phase diagram of hot and dense matter near the quark gluon plasma (QGP) phase transition. The QGP is a state in which the individual hadrons dissolve into a gas of free (or almost free) quarks and gluons in strongly compressed and hot matter (for recent reviews on the topic, we refer to [1,2]). The achievable energyand baryon densities sensitively depend on the extend to which the nuclei are stopped during penetration; they also depend on mass number and bombarding energy.Earlier RHIC estimates have been performed assuming boost-invariant hydrodynamics [3][4][5][6][7] and pQCD (Regge theory) motivated model [8,9]: baryons are concentrated at projectile and target rapidity separated by a large region which is baryon free (in position and momentum space), i.e. the nuclei are transparent. The region between them is filled by the color fields which materialize, developing a plateau in the mesons' rapidity distribution.This scenario is supported experimentally for pp-and pp-collisions at collider energies. It is the aim of the present work to examine whether this remains true also for the collision of large nuclei. From lower energy nucleus-nucleus collisions we know that only a small fraction of the total number of collisions takes place at the full incident energy while most of them take place at much lower energies. In fact, transport model studies show a fair amount of stopping at the RHIC energy with strong transverse expansion [10,11] indicating that the collision of two nuclei is more than just the superposition of "A×A" nucleon collisions at the same energy (i.e. that secondary interactions are very important at all investigated energies).As a tool for our investigation of heavy ion reactions at RHIC the Ultra-relativistic Quantum Molecular Dynamics model (UrQMD 1.2) is applied [12].Similar to the RQMD model [10,13] Let us tackle directly the relevant questions prompted by the start-up of RHIC:• Can string models like UrQMD be applied to AA reactions at RHIC energies?• Is baryonic stopping achieved at RHIC?• How many particles will be produced?• Will secondary interactions modify observables?The increasing importance of perturbative QCD effects (hard scattering) [8,9,24] and coherent parton dynamics [25] has lead to the speculations that ...

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“…The solid line represents results with the default one used in UrQMD, which was developed by Mao et al originally for free NN elastic scattering (please see Refs. [13,21] and references given therein). It is known from Mao's calculations that the differential NN elastic cross section in free space is forward-backward peaked, especially with the increase of incident energy.…”

Section: V 2 Results For Protons and Anti-protonsmentioning

confidence: 99%

“…It is known that the UrQMD model [13,14] originates from its two working parents named the quantum molecular dynamics (QMD) model [15] (whose various modified versions have been successfully used for modeling HICs at SIS and even lower energies) and the relativistic molecular dynamics (RQMD) model [16] (whose following (hybrid) versions are being used to serve mainly for HICs at energies ranging from AGS, SPS, RHIC, up to LHC), respectively. Therefore, with a continuous maintenances and updates, a large number of theoretical analyses, predictions, and comparisons with data have been supplied by the UrQMD transport model for our community, over a larger range of beam energies.…”

Section: Urqmd Model and Collective Flowsmentioning

confidence: 99%

An explanation of the elliptic flow difference between proton and anti-proton from the UrQMD model with hadron potentials

Wang

et al. 2016

Sci. China Phys. Mech. Astron.

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The time evolution of both proton and anti-proton v 2 flows from Au+Au collisions at √ s N N =7.7GeV are examined by using both pure cascade and mean-field potential versions of the UrQMD model. Due to a stronger repulsion at the early stage introduced by the repulsive potentials and hence much less annihilation probabilities, anti-protons are frozen out earlier with smaller v 2 values. Therefore, the experimental data of anti-proton v 2 as well as the flow difference between proton and anti-proton can be reasonably described with the potential version of UrQMD.

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Are We Close to an Equilibrated Quark-Gluon Plasma? Nonequilibrium Analysis of Particle Production in Ultrarelativistic Heavy Ion Collisions

Cited by 35 publications

References 45 publications

SQM 2006: theory summary and perspectives

SQM 2006: theory summary and perspectives

Global observables and secondary interactions in central Au+Au reactions ats=200AGeV

An explanation of the elliptic flow difference between proton and anti-proton from the UrQMD model with hadron potentials

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