标题： 影响参数对GSI/SIS相对论重离子碰撞热力学描述的影响 显示英文标题

标题： Influence of Impact Parameter on Thermal Description of Relativistic Heavy Ion Collisions at GSI/SIS

摘要： 人们注意到系统大小在SIS能区相对论重离子碰撞中粒子产额的热力学分析中所起的作用。这一点体现在1至2A GeV能区 $AA$ 碰撞中K+和K-产额相对于 participant 数目的非线性依赖关系上。研究表明这种依赖关系可以用一个具有规范奇异数守恒的热模型很好地定量描述。此外，在0.8至2.0A GeV能区Au-Au和Ni-Ni碰撞中心碰撞情形下测量到的粒子多重数比值（π+/p, π-/π+, d/p, K+/π+和K+/K-, 但不包括η/π0）也可以用具有统一冻结温度和化学势的热模型来解释。引入集体流的概念后，推导出了粒子能量分布的一致图像，其中流速强烈依赖于碰撞参数。 显示英文摘要

摘要： Attention is drawn to the role played by the size of the system in the thermodynamic analysis of particle yields in relativistic heavy ion collisions at SIS energies. This manifests itself in the non-linear dependence of K+ and K- yields in $AA$ collisions at 1 -- 2 A.GeV on the number of participants. It is shown that this dependence can be quantitatively well described in terms of a thermal model with a canonical strangeness conservation. The measured particle multiplicity ratios (pi+/p, pi-/pi+, d/p, K+/pi+ and K+/K- but not eta/pi0) in central Au-Au and Ni-Ni collisions at 0.8 -- 2.0 A.GeV are also explained in the context of a thermal model with a common freeze-out temperature and chemical potential. Including the concept of collective flow a consistent picture of particle energy distributions is derived with the flow velocity being strongly impact-parameter dependent.