Effects of equation of state on nuclear suppression and the initial entropy density of quark gluon plasma

Abstract

We study the effects of the equation of state on the nuclear suppression of heavy flavours in quark gluon plasma and estimate the initial entropy density of the system produced at the highest RHIC energy. For this purpose we have used the experimental data on the charged particle multiplicity and the nuclear suppression of single electron spectra originating from the semi-leptonic decays of open charm and beauty mesons. We have used inputs from lattice QCD to minimize the model dependence of the results. We obtain the value of the initial entropy density which varies from 20 to 59 /fm 3 depending on the value of the velocity of sound that one uses for the analysis. Our investigation leads to a conservative value of the initial entropy density ∼ 20/fm 3 with corresponding initial temperature ∼ 210 MeV well above the value of the transition temperature predicted by lattice QCD. PACS numbers: 12.38.Mh,24.85.+p,25.75.Nq A thermalized system of quarks and gluons, called quark gluon plasma (QGP) is expected to be formed in the collisions of two nuclei at ultra-relativistic energies [1]. Rigorous experimental and theoretical efforts are on to create and characterize this novel, deconfined phase of quarks and gluons. Lattice QCD (LQCD) calculations indicate that at a temperature ∼ 175 MeV the entropy density (s) of the hadronic matter rises significantly due to the release of colour degrees of freedom which are confined within the hadrons at zero temperature. Therefore, it is of foremost importance to determine the value of the initial entropy density (s i ) / initial temperature (T i ) for the system formed in nuclear collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) and assess whether the system is formed in colour deconfined phase or not. The focus of the present study is to estimate s i or T i of the system formed at Au+Au collisions at √ s NN = 200 GeV. For this purpose we strict to take inputs from experimental data and LQCD calculations to minimize the model dependence of the outcome of the present analysis.One of the possible way to estimate the value of the initial entropy density is the extrapolation of the measured (final) observables backward in time through a suitable dynamical model. In absence of viscous loss the time reversal symmetry of the system is valid, therefore, the measured multiplicity at the freeze-out of the system can be used to estimate s i . The s i and the thermalization time (τ i ) are constrained by the measured (final) hadron multiplicity (dN/dy) by the following relation [2]:where A ⊥ is the transverse area of the system can be determined from the collision geometry and κ is a known constant (=3.7 for massless bosons like pions). The value of dN/dy which is connected to s i through Eq. 1 is readily available for different collision centralities [1]. In Eq. 1 there are two unknown quantities, τ i and s i both of which can not be determined from a single equation involving a single measured the dN/dy. Therefore, we choose another experimentally measur...

Nonconformal holographic model forD-meson suppression at energies available at the CERN Large Hadron Collider

“…It is quite expected as the non-conformal drag forces suppressed by a factor 2-4 as compare to conformal case (in Fig 1 and Fig 2) depending on temperature and momentum. Apart from the drag force, the conformal and non-conformal AdS follow different Einstein relation to have the diffusion coefficients as well as they have different EOS [57] which indeed affect the RAA [12,24]. Considering only the collisional loss within the non-conformal holographic fail to reproduced the experimental data.…”

“…1 and 2) depending on temperature and momentum. Apart from the drag force, the conformal and nonconformal AdS models follow different Einstein relations in order to have different diffusion coefficients as well as different EOS [56], which indeed affect the RAA [12,57,58]. Considering only the collisional loss within the nonconformal holographic model fails to reproduce the experimental data.…”

Charm quark energy loss in infinite QCD matter using a parton cascade model

“…35-4.5 GeV and T = 300 MeV, this ratio is found to be∼ 5 and suggests that relaxation time for heavy quarks is larger than that of light quarks and gluons. If thermalization time, τ q/g , is taken to be O(1fm/c), and if equilibrium temperature, T i and freeze-out temperature, T f are taken as 300 MeV and 170 MeV [9] respectively, then the lifetime of the QGP can be approximately shown to be 5 fm/c. This might imply that the heavy quark relaxation time for T= 300 MeV is comparable to the QGP lifetime at this condition.…”