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arXiv 0812.3393nucl-thhep-phnucl-ex
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相对论重离子碰撞早期动力学中的自由流近似

Free-streaming approximation in early dynamics of relativistic heavy-ion collisions

Wojciech Broniowski, Wojciech Florkowski, Mikolaj Chojnacki, Adam Kisiel

摘要:

我们研究了相对论性重离子碰撞中早期动力学的一个近似,其中形成后的部分子是自由流动的,并在适当的时间1 fm/c附近经历了朗道匹配条件中描述的突然平衡。我们讨论这种方法的物理和形式方面。特别是,我们表明,初始方位不对称的横向流动发展为非中心碰撞的突然平衡的后果。此外,从自由流动阶段的能量动量张量匹配非常顺利的横向流体动力学中使用的形式,而匹配各向同性流体动力学需要一个更显着的变化的能量动量张量。在流体动力学相之后,借助于THERMINATOR进行统计强子化。在我们的方法中,对横动量谱、椭圆流和Hanbury-Brown-Twiss关联半径,包括Rout/Rside以及半径对方位角的依赖关系(azHBT)的物理结果进行了适当的描述。对于在0.25 fm/c的早期适当时间开始的纯流体动力学演化,或者对于在那个时间开始的自由流动,随后在τ ~1 fm/c突然平衡,然后通过完美的流体动力学,该协议同样良好。因此,包含自由流允许我们将流体动力学的开始延迟到1 fm/c量级的更现实的时间。

英文摘要:

We investigate an approximation to early dynamics in relativistic heavy-ion collisions, where after formation the partons are free streaming and around the proper time of 1 fm/c undergo a sudden equilibration described in terms of the Landau matching condition. We discuss physical and formal aspects of this approach. In particular, we show that initial azimuthally asymmetric transverse flow develops for non-central collisions as a consequence of the sudden equilibration. Moreover, the energy-momentum tensor from the free-streaming stage matches very smoothly to the form used in the transverse hydrodynamics, whereas matching to isotropic hydrodynamics requires a more pronounced change in the energy-momentum tensor. After the hydrodynamic phase statistical hadronization is carried out with the help of THERMINATOR. The physical results for the transverse-momentum spectra, the elliptic-flow, and the Hanbury-Brown--Twiss correlation radii, including the ratio R_out/R_side as well as the dependence of the radii on the azimuthal angle (azHBT), are properly described within our approach. The agreement is equally good for a purely hydrodynamic evolution started at an early proper time of 0.25 fm/c, or for the free streaming started at that time, followed by the sudden equilibration at tau ~1 fm/c and then by perfect hydrodynamics. Thus, the inclusion of free streaming allows us to delay the start of hydrodynamics to more realistic times of the order of 1 fm/c.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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