Chemical equilibration of an expanding quark-gluon plasma

Srivastava, D. K.; Mustafa, Munshi G.; Müller, Berndt

doi:10.1016/s0370-2693(97)00090-7

Cited by 29 publications

(48 citation statements)

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“…This separation could even be made easier by measuring the p ⊥ distribtuion of the lepton pairs. In a future publication we shall report the result of the transverse hydrodynamic flow of the plasma on these conclusions [18].…”

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confidence: 88%

“…The QGP expected to be produced at RHIC and LHC is likely to be far from chemical equilibrium, initially. Chemical reactions among the partons will then push it towards a chemical equilibrium [16][17][18]. The evolution of the temperature and the quark and gluon fugacities 1 at RHIC and LHC eneriges has recently been obtained [18] for such a scenario with initial conditions from a Self Screened Parton Cascade Model [19].…”

mentioning

confidence: 99%

“…This leads to a rather large drag of ∼ 1.6/fm at RHIC and ∼ 2.7/fm at LHC on charm quarks at τ = τ i , where τ i = 0.25 fm/c is determined by the onset of the kinetic equilibrium [18]. This has a very important implication.…”

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confidence: 99%

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Radiative energy-loss of heavy quarks in a quark-gluon plasma

et al. 1998

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We estimate the radiative energy-loss of heavy quarks, produced from the initial fusion of partons, while propagating in a quark-gluon plasma which may be formed in the wake of relativistic heavy ion collisions. We find that the radiative energy-loss for heavy quarks is larger than the collisional energy-loss for all energies. We point out the consequences on possible signals of the quark-gluon plasma.One of the most interesting predictions of QCD is the transition from the confined/chirally broken phase to the deconfined/chirally symmetric state of quasi-free quarks and gluons, the so-called quark-gluon plasma (QGP). Relativistic heavy ion collisions are being studied with the intention of investigating the properties of the QGP [1]. While experiments at AGS and SPS continue, new experiments have been planned at RHIC and LHC with centre of mass energies 200 AGeV and 5.5 ATeV, respectively. During the past decade many different signatures of the transition to the QGP have been proposed. A promising example is the emission of penetrating probes such as dileptons and single photons, which can reveal the early parton dynamics and the history of evolution of the plasma. Similarly, the production and propagation of open charm and high energy jets in a dense medium, can provide information [2] about parton scattering and thermalization of the partonic system. Jets are expected to show up at collider energies at RHIC and LHC.Heavy quark pairs are mostly produced from the initial fusion of partons (mostly from gg → QQ, but also from qq → QQ, where q denotes one of the lighter quarks and Q is a heavy quark) of the colliding nucleons and also from the QGP, if the initial temperature is high enough, which is likely to be achieved at RHIC and LHC energies. The charm quarks will be produced on a time scale of 1/2m c 0.07 fm/c, which would be as low as 0.02 fm/c for bottom quarks. There is no production of heavy quarks at late times in the QGP and none in the hadronic matter. Thus, the total number of heavy quarks gets frozen very early in the history of the collision which makes them a good candidate for a probe of the QGP. Immediately upon their production, these heavy quarks will propagate through the deconfined matter and start losing energy. The energy-loss suffered by these quarks will determine the shape of the dilepton spectra produced from correlated charm (or bottom) decay which provides a large background to dilepton production from annihilation of quarks in the plasma. We shall come back to this aspect towards the end of this Letter.There are two contributions to the energy-loss of a heavy quark in the QGP: one caused by elastic collisions with the light partons of the QGP and the other by radiation of the decelerated color charge, i.e., bremsstrahlung of gluons. There is an extensive body of literature [3][4][5][6][7][8] on the collisional energy-loss of energetic quarks considering elastic collisions with the quarks and gluons (Qg → Qg and Qq → Qq) of the dense medium. A complete leading order result for the col...

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Radiative energy-loss of heavy quarks in a quark-gluon plasma

et al. 1998

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“…We solve these equations using well established methods [13] with initial energy density profiles as before and plot the constant energy density contours [14,15] appropriate for = s to get τ s (r). Rest of the treatment follows as before.…”

Section: Transverse Expansion Of the Plasmamentioning

confidence: 99%

Determination of the equation of state of quark matter from $J/\psi$ and $\Upsilon$ suppression at RHIC and LHC

Pal¹,

Patra²,

Srivastava³

2000

Eur. Phys. J. C

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The long life-time of the quark-gluon plasma likely to be created in the relativistic heavy ion collisions at RHIC and LHC energies renders it sensitive to the details of the equation of state of the quark-matter. We show that the p T dependence of the survival probability of the directly produced J/ψ at RHIC energies and that of the directly produced Υ at LHC energies is quite sensitive to the speed of sound in the quark matter, which relates the pressure and the energy density of the plasma. The transverse expansion of the plasma is shown to strongly affect the J/ψ suppression at LHC energies.

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“…They start with the assumption of some initial density, tempertaure, pressure, and an equation of state and study the evolution of the system under the assumption of thermodynamic equilibrium, as well as, the applicability of hydrodynamics. At very high energies one may obtain [2] the intitial conditions from, e.g, a self screened parton cascade model or the HIJING model. At SPS energies they are often obtained (see e.g., Ref.…”

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Spectra of produced particles at CERN SPS heavy-ion collisions from a parton cascade model

Srivastava

Geiger

1998

Physics Letters B

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We evaluate the spectra of produced particles (pions, kaons, antiprotons) from partonic cascades which may develop in the wake of heavy-ion collisions at CERN SPS energies and which may hadronize by formation of clusters which decay into hadrons. Using the experimental data obtained by NA35 and NA44 collaborations for S+S and Pb+Pb collisions, we conclude that the Monte Carlo implementation of the recently developed parton-cascade/cluster-hadronization model provides a reasonable description of the distributions of the particles produced in such collisions. While the rapidity distribution of the mid-rapidity protons is described reasonably well, their transverse momentum distribution falls too rapidly compared to the experimental values, implying a significant effect of final state scattering among the produced hadrons neglected so far.PACS numbers: 12.38. Bx, 12.38.Mh, 25.75.+r, 24.85.+p With the advent of heavy-ion beams and experiments at the CERN SPS, it seems for the first time to be possible to create strongly interacting matter at such high density that a thermal state of colored partons, deconfined over a macroscopic volume, may be formed and live sufficiently long to leave traces on the hadronic final state. The presence of such an exotic high-density parton state, a quark-gluon-plasma (QGP), should be mirrored in characteristic features of particle production. Specifically, the changing characteristics of particle production in dense and hot matter should teach us about the partonic components in the system and the QCD dynamics being responsible for a QGP formation. The study of the evolution of particle production is therefore the prime tool to identify the observables which signal the presence of a QGP, since this ephemeral state of exotic matter is expected to lead to a copius production of secondaries including photons, dileptons, and heavy mesons, all of which may carry some information about the nature of the highly compressed QCD matter.A large body of data has already accumulated about the spectra of particles produced in such collisions at SPS energies. It is well known that a large part of these spectra can be explained quite well using either thermal models, or hydrodynamic models, or one of the several models based on string phenomenology. What does the success of these models imply and what does it portend for the search of a QGP? What information can we reliably obtain about the early stages of the evolution from these studies?Thermal models, in principle deal with the situation which prevails just before the particles freeze-out when they are assumed to be in thermal and some degree of chemical equilibrium. This along with a parametrized transverse velocity profile then provides the description of the particle spectra (see e.g., Ref.[1]). Note however that, a complete thermodynamic equilibrium will also mean a complete loss of memory of the initial state, which we have to infer by extrapolating the densities and temperatures backwards in time, familiar in cosmological studies....

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Chemical equilibration of an expanding quark-gluon plasma

Cited by 29 publications

References 14 publications

Radiative energy-loss of heavy quarks in a quark-gluon plasma

Radiative energy-loss of heavy quarks in a quark-gluon plasma

Determination of the equation of state of quark matter from $J/\psi$ and $\Upsilon$ suppression at RHIC and LHC

Spectra of produced particles at CERN SPS heavy-ion collisions from a parton cascade model

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