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arXiv 1209.0042hep-phnucl-th
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LHC能区p + p和Pb + Pb碰撞中2 π HBT关联的UrQMD计算

UrQMD calculations of two-pion HBT correlations in p+p and Pb+Pb collisions at LHC energies

Qingfeng Li, Gunnar Graef, Marcus Bleicher

备注：
9 pages, 4 figures, 1 table. Talk given by Qingfeng Li at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS)
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摘要：

采用超相对论量子分子动力学模型，结合关联加力燃烧室，研究了大型强子对撞机（LHC）能区p + p碰撞和中心Pb + Pb碰撞的2 π Hanbury-Brown-Twiss（HBT）关联.普拉特-伯奇HBT半径$R_{long}$、$R_{out}$和$R_{side}$的横向动量依赖性是从纵向同向移动系统中的相关器的三维高斯拟合中提取的。在p + p的情况下，相关的带电粒子的多重性和形成时间的依赖性进行了探讨，数据允许约束的形成时间在字符串的碎片$τ_f \leq 0.8$ fm/c。在Pb + Pb的情况下，发现$R_{out}$被高估了近50%。LHC的结果也进行了比较，从在RHIC的STAR实验的数据。对于这两种能量，我们发现，计算的$R_{out}/R_{side}$比总是大于数据，这表明在模型中的排放是爆炸性小于观察到的数据。

英文摘要：

Two-pion Hanbury-Brown-Twiss (HBT) correlations for p+p and central Pb+Pb collisions at the Large-Hadron-Collider (LHC) energies are investigated with the ultra-relativistic quantum molecular dynamics model combined with a correlation afterburner. The transverse momentum dependence of the Pratt-Bertsch HBT radii $R_{long}$, $R_{out}$, and $R_{side}$ is extracted from a three-dimensional Gaussian fit to the correlator in the longitudinal co-moving system. In the p+p case, the dependence of correlations on the charged particle multiplicity and formation time is explored and the data allows to constrain the formation time in the string fragmentation to $τ_f \leq 0.8$ fm/c. In the Pb+Pb case, it is found that $R_{out}$ is overpredicted by nearly 50%. The LHC results are also compared to data from the STAR experiment at RHIC. For both energies we find that the calculated $R_{out}/R_{side}$ ratio is always larger than data, indicating that the emission in the model is less explosive than observed in the data.

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