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Time evolution of Mach-like structure in a partonic transport model

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 Added by Yu-Gang Ma
 Publication date 2006
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and research's language is English




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The time evolution of Mach-like structure (the splitting of the away side peak in di-hadron $Deltaphi$ correlation) is presented in the framework of a dynamical partonic transport model. With the increasing of the lifetime of partonic matter, Mach-like structure can be produced and developed by strong parton cascade process. Not only the splitting parameter but also the number of associated hadrons ($N_{h}^{assoc}$) increases with the lifetime of partonic matter and partonic interaction cross section. Both the explosion of $N_{h}^{assoc}$ following the formation of Mach-like structure and the corresponding results of three-particle correlation support that a partonic Mach-like shock wave can be formed by strong parton cascade mechanism. Therefore, the studies about Mach-like structure may give us some critical information, such as the lifetime of partonic matter and hadronization time.



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74 - G. L. Ma , S. Zhang , Y. G. Ma 2006
In the framework of a multi-phase transport model (AMPT) with both partonic and hadronic interactions, azimuthal correlations between trigger particles and associated scattering particles have been studied by the mixing-event technique. The momentum ranges of these particles are $3< p^{trig}_T< 6$ GeV/$c$ and $0.15< p_{T}^{assoc} < 3$ GeV/$c$ (soft), or $2.5<p^{trig}_T<$ 4 GeV/$c$ and $1< p_{T}^{assoc} < 2.5$ GeV/$c$ (hard) in Au + Au collisions at $sqrt{s_{NN}}$ = 200 GeV. A Mach-like structure has been observed in correlation functions for central collisions. By comparing scenarios with and without parton cascade and hadronic rescattering, we show that both partonic and hadronic dynamical mechanisms contribute to the Mach-like structure of the associated particle azimuthal correlations. The contribution of hadronic dynamical process can not be ignored in the emergence of Mach-like correlations of the soft scattered associated hadrons. However, hadronic rescattering alone cannot reproduce experimental amplitude of Mach-like cone on away-side, and the parton cascade process is essential to describe experimental amplitude of Mach-like cone on away-side. In addition, both the associated multiplicity and the sum of $p_{T}$ decrease, whileas the $<p_{T}>$ increases, with the impact parameter in the AMPT model including partonic dynamics from string melting scenario.
Using the string melting version of a multiphase transport (AMPT) model, we focus on the evolution of thermodynamic properties of the central cell of parton matter produced in Au+Au collisions ranging from 200 GeV down to 2.7 GeV. The temperature and baryon chemical potential are calculated for Au+Au collisions at different energies to locate their evolution trajectories in the QCD phase diagram. The evolution of pressure anisotropy indicates that only partial thermalization can be achieved, especially at lower energies. Through event-by-event temperature fluctuations, we present the specific heat of the partonic matter as a function of temperature and baryon chemical potential that is related to the partonic matters approach to equilibrium.
112 - Y. G. Ma , G.L. Ma , S. Zhang 2006
In a framework of a multi-phase transport model with both partonic and hadronic interactions, azimuthal correlations between trigger particles and associated scattering particles in Au + Au collisions at $sqrt{s_{NN}}$ = 200 GeV/$c$ have been studied by the mixing-event technique. The Mach-like structure has been observed in correlation function for central collisions. It is shown that the Mach-like structure is basically born in the partonic process and further developed in hadronic rescattering process. However, hadronic rescattering alone cannot reproduce the amplitude of Mach-like cone on away side, therefore partonic cascade process is necessary to describe the amplitude of Mach-like cone on away side in experiment. In addition, three-particle correlations have been investigated in central Au + Au collisions with the AMPT model, and the results support the conclusion that partonic cascade processes enhance the opening angle of Mach-like cone structures.
A Linearized Boltzmann Transport (LBT) model coupled with hydrodynamical background is established to describe the evolution of jet shower partons and medium excitations in high energy heavy-ion collisions. We extend the LBT model to include both elastic and inelastic processes for light and heavy partons in the quark-gluon plasma. A hybrid model of fragmentation and coalescence is developed for the hadronization of heavy quarks. Within this framework, we investigate how heavy flavor observables depend on various ingredients, such as different energy loss and hadronization mechanisms, the momentum and temperature dependences of the transport coefficients, and the radial flow of the expanding fireball. Our model calculations show good descriptions of the $D$ meson suppression and elliptic flow observed at the LHC and RHIC. The prediction for the Pb-Pb collisions at $sqrt{s_mathrm{NN}}$=5.02~TeV is provided.
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