标题： 200 A GeV/c S+Au碰撞的流体力学描述：强子和电磁谱 显示英文标题

标题： Hydrodynamical Description of 200 A GeV/c S+Au Collisions: Hadron and Electromagnetic Spectra

摘要： 我们利用流体动力学方法研究了200 A GeV/c能级下的S+Au相对论碰撞。 我们测试了多种状态方程（EOS），这些方程用于描述在CERN-SPS重离子实验中可达到的高密度强相互作用物质。 对于每种状态方程，都可以确定合适的初始条件来重现实验中的强子谱；这突显了在这种方法中初始条件与状态方程之间的模糊性。 同时，我们计算了由此产生的热光子和双电子谱，并与实验数据进行比较。 如果允许随着温度升高激发共振态，具有和不具有相变的情景所产生的电磁信号非常相似，在当前的实验分辨率下无法分辨。 关于CERES双轻子数据，考虑的所有状态方程与标准领头阶双轻子速率结合后，都无法重现ρ峰以下观察到的双轻子过剩现象。 然而，我们的工作表明，改进测量光子和双轻子谱的能力有可能极大地限制状态方程。 显示英文摘要

摘要： We study relativistic S+Au collisions at 200 A GeV/c using a hydrodynamical approach. We test various equations of state (EOSs), which are used to describe the strongly interacting matter at densities attainable in the CERN-SPS heavy ion experiments. For each EOS, suitable initial conditions can be determined to reproduce the experimental hadron spectra; this emphasizes the ambiguity between the initial conditions and the EOS in such an approach. Simultaneously, we calculate the resulting thermal photon and dielectron spectra, and compare with experiments. If one allows the excitation of resonance states with increasing temperature, the electro-magnetic signals from scenarios with and without phase transition are very similar and are not resolvable within the current experimental resolution. With regard to the CERES dilepton data, none of the EOSs considered, in conjunction with the standard leading order dilepton rates, succeed in reproducing the observed excess of dileptons below the rho peak. Our work, however, suggests that an improved measurement of the photon and dilepton spectra has the potential to strongly constrain the EOS.