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arXiv 1102.3624nucl-th
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相对论重离子碰撞早期部分子相互作用产生双轻子

Dilepton production from parton interactions in the early stage of relativistic heavy-ion collisions

O. Linnyk, E. L. Bratkovskaya, J. Manninen, W. Cassing

摘要:

利用部分子-强子-弦动力学(PHSD)离壳输运方法研究了相对论重离子碰撞早期部分子相互作用产生双轻子的过程。PHSD中部分子的描述基于动力学准粒子模型(DQPM),该模型与热力学平衡下的格点量子色动力学结果相匹配。根据DQPM理论,强相互作用夸克-胶子等离子体(sQGP)的组成是具有宽谱函数的大质量离壳准粒子(夸克和胶子)。为了解决sQGP的电磁辐射问题,我们从DQPM出发,考虑夸克和胶子的有效传播子,导出了q+qbar->gamma*,q+qbar->gamma*+g和q+g->gamma*+q(qbar+g->gamma*+qbar)反应的离壳截面.通过将这些离壳过程应用到PHSD输运方法中,计算了158 AGeV的In+In碰撞和200 GeV的Au+Au碰撞中双轻子的产生.通过与NA 60和PHENIX合作组的数据比较,研究了不同双轻子产生机制的相对重要性,指出了部分子通道占主导地位的相空间区域。

英文摘要:

We address the dilepton production from the parton interactions in the early stage of relativistic heavy-ion collisions within the parton-hadron-string dynamics (PHSD) off-shell transport approach. The description of partons in PHSD is based on the dynamical quasiparticle model (DQPM) matched to reproduce lattice QCD results in thermodynamic equilibrium. According to the DQPM the constituents of the strongly interacting quark-gluon plasma (sQGP) are massive and off-shell quasi-particles (quarks and gluons) with broad spectral functions. In order to address the electromagnetic radiation of the sQGP, we derive off-shell cross sections of q+qbar->gamma*, q+qbar->gamma*+g and q+g->gamma*+q (qbar+g->gamma*+qbar) reactions taking into account the effective propagators for quarks and gluons from the DQPM. Dilepton production in In+In collisions at 158 AGeV and in Au+Au at sqrt(s)=200 GeV is calculated by implementing these off-shell processes into the PHSD transport approach. By comparing to the data of the NA60 and PHENIX Collaborations, we study the relative importance of different dilepton production mechanisms and point out the regions in phase space where partonic channels are dominant.

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