arXiv 0704.36762007-04-28hep-ph

夸克-胶子等离子体的虚光子发射

Virtual Photon Emission from Quark-Gluon Plasma

S. V. Suryanarayana

备注：: 8 pages 8 figures, phenomenological formulae for photon emission
发表信息：: Phys.Rev.C76:044903,2007
DOI：: 10.1103/PhysRevC.76.044903

摘要：

最近，我们提出了一个经验方法的Landau-Pomeranchuk-Migdal（LPM）效应的光子发射的夸克胶子等离子体作为光子质量的函数。这种方法是基于广义发射函数（GEF）的光子发射，在一个固定的温度和强耦合常数。在目前的工作中，我们已经扩展了几个温度和强耦合强度的LPM计算。考虑韧致辐射和$\bf aws$过程，用变量集\{ $p_0,q_0,Q^2,T,α_s$ \}的迭代法求解（${\bf \tilde{f}(\tilde{p}_\perp)}$）和（$\tilde{g}({\bf \tilde{p}_\perp})$）的积分方程.我们推广了韧致辐射和{ \bf aws}过程的动力学标度变量$x_T$，$x_L$，它们现在是变量$p_0,q_0,Q^2,T,α_s$的函数.前面介绍的GEF，$g^b_T$、$g^a_T$、$g^b_L$、$g^a_L$，也适用于任何温度和耦合强度。由此，作为光子质量和能量的函数的光子偏振张量的虚部可以被计算为对等离子体中的这些GEF和部分子分布函数的一维积分。然而，对于实验数据的唯象研究，需要一个不涉及部分子动量积分的简单经验公式。因此，我们提出了一个唯象公式的虚光子偏振张量的函数\{ $q_0,Q^2,T,α_s$ \}，其中包括韧致辐射和$\bf aws$机制以及LPM效应。

英文摘要：

We recently proposed an empirical approach for the Landau-Pomeranchuk-Migdal (LPM) effects in photon emission from the quark gluon plasma as a function of photon mass. This approach was based on Generalized Emission Functions (GEF) for photon emission, derived at a fixed temperature and strong coupling constant. In the present work, we have extended the LPM calculations for several temperatures and strong coupling strengths. The integral equations for (${\bf \tilde{f}(\tilde{p}_\perp)}$) and ($\tilde{g}({\bf \tilde{p}_\perp})$) are solved by the iterations method for the variable set \{$p_0,q_0,Q^2,T,α_s$\}, considering bremsstrahlung and $\bf aws$ processes. We generalize the dynamical scaling variables, $x_T$, $x_L$, for bremsstrahlung and {\bf aws} processes which are now functions of variables $p_0,q_0,Q^2,T,α_s$. The GEF introduced earlier, $g^b_T$, $g^a_T$, $g^b_L$, $g^a_L$, are also generalized for any temperatures and coupling strengths. From this, the imaginary part of the photon polarization tensor as a function of photon mass and energy can be calculated as a one dimensional integral over these GEF and parton distribution functions in the plasma. However, for phenomenological studies of experimental data, one needs a simple empirical formula without involving parton momentum integrations. Therefore, we present a phenomenological formula for imaginary photon polarization tensor as a function of \{$q_0,Q^2,T,α_s$\} that includes bremsstrahlung and $\bf aws$ mechanisms along with LPM effects.

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