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arXiv 1002.1165nucl-thhep-ph
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RHIC重离子碰撞中的体物质演化和喷流输运参数提取

Bulk matter evolution and extraction of jet transport parameter in heavy-ion collisions at RHIC

Xiao-Fang Chen, Carsten Greiner, Enke Wang, Xin-Nian Wang, Zhe Xu

摘要:

在多重部分子散射和胶子韧致辐射引起的喷注猝灭的图像中,部分子碎裂函数的介质修正和大横动量强子谱的抑制受喷注输运参数沿喷注传播路径的大小和时空分布的控制。在介质修正碎裂函数的高扭(HT)方法和次领先阶(NLO)微扰QCD(pQCD)部分子模型中,分析了RHIC能区的离子碰撞.假设喷注输运参数$\hat q$与QGP和强子相的粒子数密度成正比,核靶深度非弹性散射(DIS)中喷注猝灭的实验数据可以为热强子物质中的$\hat q_{h}$提供指导。然后可以研究在初始时刻$τ_{0}$提取的射流猝灭参数$\hat q_{0}$的初始值对体相介质演化的依赖性。考察了横向膨胀、径向流动、相变和非平衡演化的影响。计算结果表明,在(1+3)d理想流体动力学模型中的$\hat q_{0}τ_{0}= 0.54$为$\hat q_{0}τ_{0}= 0.54$ GeV $^{2}$,在级联模型中的$^{2}$为0.96 GeV $^{2}$,主要差别来自于初始的非平衡演化和后来的强子演化.强子相对喷流猝灭的总贡献约为22- 44%,是显著的。因此,对高能重离子碰撞中强相互作用QGP相喷注输运参数的精确提取,对早期非平衡部分子演化和后期强子相互作用的真实描述是至关重要的.

英文摘要:

Within the picture of jet quenching induced by multiple parton scattering and gluon bremsstrahlung, medium modification of parton fragmentation functions and therefore the suppression of large transverse momentum hadron spectra are controlled by both the value and the space-time profile of the jet transport parameter along the jet propagation path. Experimental data on single hadron suppression in high-energy heavy-ion collisions at the RHIC energy are analyzed within the higher-twist (HT) approach to the medium modified fragmentation functions and the next-to-leading order (NLO) perturbative QCD (pQCD) parton model. Assuming that the jet transport parameter $\hat q$ is proportional to the particle number density in both QGP and hadronic phase, experimental data on jet quenching in deeply inelastic scattering (DIS) off nuclear targets can provide guidance on $\hat q_{h}$ in the hot hadronic matter. One can then study the dependence of extracted initial value of jet quenching parameter $\hat q_{0}$ at initial time $τ_{0}$ on the bulk medium evolution. Effects of transverse expansion, radial flow, phase transition and non-equilibrium evolution are examined. The extracted values are found to vary from $\hat q_{0}τ_{0}= 0.54$ GeV$^{2}$ in the (1+3)d ideal hydrodynamic model to 0.96 GeV$^{2}$ in a cascade model, with the main differences coming from the initial non-equilibrium evolution and the later hadronic evolution. The overall contribution to jet quenching from the hadronic phase, about 22-44%, is found to be significant. Therefore, realistic description of the early non-equilibrium parton evolution and later hadronic interaction will be critical for accurate extraction of the jet transport parameter in the strongly interacting QGP phase in high-energy heavy-ion collisions.

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