粗粒化方法中的矢量介子谱函数
Vector Meson Spectral Functions in a Coarse-Graining Approach
摘要：
在重离子碰撞在顶部SPS能量的双轻子生产的粗粒化的方法，结合了潜在的微观演变的核反应与应用程序的介质修改的光谱功能。提取小时空网格的局部能量和重子密度，并进入每个单元的静止框架，可以通过应用状态方程确定局部温度和化学势。这使得计算热双轻子发射。我们应用和比较两种不同的谱函数的$ρ$：强子多体计算和一种方法，使用经验散射振幅。两个谱函数的模型计算与NA60合作的数据取得了很好的一致性，但在细节上强子多体方法导致更好的描述，特别是在$ρ$的极质量周围的加宽和低质量的过剩。我们进一步表明，π介子化学势的存在显着影响双轻子产额。
英文摘要：
Dilepton production in heavy-ion collisions at top SPS energy is investigated within a coarse-graining approach that combines an underlying microscopic evolution of the nuclear reaction with the application of medium-modified spectral functions. Extracting local energy and baryon density for a grid of small space-time cells and going to each cell's rest frame enables to determine local temperature and chemical potential by application of an equation of state. This allows for the calculation of thermal dilepton emission. We apply and compare two different spectral functions for the $ρ$: A hadronic many-body calculation and an approach that uses empirical scattering amplitudes. Quantitatively good agreement of the model calculations with the data from the NA60 collaboration is achieved for both spectral functions, but in detail the hadronic many-body approach leads to a better description, especially of the broadening around the pole mass of the $ρ$ and for the low-mass excess. We further show that the presence of a pion chemical potential significantly influences the dilepton yield.
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