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arXiv 1702.05906nucl-th
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超相对论重离子碰撞中的虚光子极化

Virtual photon polarization in ultrarelativistic heavy-ion collisions

Gordon Baym, Tetsuo Hatsuda, Michael Strickland

备注：
6 pages, 3 figures
发表信息：
Phys. Rev. C 95, 044907 (2017)
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摘要：

在超相对论性重离子碰撞中产生的直接光子的偏振反映了碰撞中产生的夸克-胶子等离子体的动量各向异性。本文提出了一个一般的框架，在等离子体中的光子光谱函数的基础上，分析角分布，从而极化的双轻子的等离子体动量各向异性。双轻子的生产率取决于，在一般情况下，四个独立的光谱函数，对应于两个横向偏振，一个纵向偏振，和-在等离子体中的动量各向异性是不是不变的奇偶校验下在当地的休息框架的问题-一个新的光谱函数，$ρ_n$，有关的各向异性方向的碰撞。动量各向异性出现在两个横向谱函数的差异中，以及在$ρ_n$中。作为一个例子，我们描述了夸克-反夸克湮灭为虚光子的最低阶Drell-Yan过程中产生的双轻子对的谱函数。

英文摘要：

The polarization of direct photons produced in an ultrarelativistic heavy-ion collision reflects the momentum anisotropy of the quark-gluon plasma created in the collision. This paper presents a general framework, based on the photon spectral functions in the plasma, for analyzing the angular distribution and thus the polarization of dileptons in terms of the plasma momentum anisotropies. The rates of dilepton production depend, in general, on four independent spectral functions, corresponding to two transverse polarizations, one longitudinal polarization, and -- in plasmas in which the momentum anisotropy is not invariant under parity in the local rest frame of the matter -- a new spectral function, $ρ_n$, related to the anisotropy direction in the collision. The momentum anisotropy appears in the difference of the two transverse spectral functions, as well as in $ρ_n$. As an illustration, we delineate the spectral functions for dilepton pairs produced in the lowest order Drell-Yan process of quark-antiquark annihilation to a virtual photon.

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