arXiv 0906.37762009-06-20nucl-ex

从RHIC的PHENIX看喷流和潜在事件在p+p和d+Au碰撞中的作用

Understanding the Role of Jet and Underlying Event in p+p and d+Au Collisions from PHENIX at RHIC

Jiangyong Jia

备注：: 19 pages, 14 figures, Writeup for Posters Presented at 21st International Conference On Ultra-Relativistic Nucleus-Nucleus Collisions (QM2009) 30 Mar - 4 Apr 2009, Knoxville, Tennessee

摘要：

双强子方位相关测量揭示了RHIC中重离子碰撞产生的稠密介质对喷流的显著改变。一个重要的问题是，这种变化在多大程度上可以归因于冷核物质效应。在该分析中，我们使用高统计RUN 8 d+Au最小偏差数据进行了相关模式的详细映射。在低和中等$p_T$下观察到喷流对产额的显著标度行为。发现喷流对产率相对于$N_{\rm coll}$缩放的p+p喷流对产率提高。喷注对产额的核修正因子$J_{\rm dAu}$似乎与$p_T^{\rm sum}$ = $p_T^a+p_T^b$（标度和）成比例，并在$p_T^{\rm sum}<$ 5- 7 GeV/c处显示出特征性的克罗宁样增强。有趣的是，近侧和远侧对之间的产量修改的水平是相似的，并且射流形状相对于p+p碰撞没有修改。研究了p+p和d+Au碰撞中喷注峰下的基座产额。在p+p碰撞的基座产量被发现是大于PYTHIA计算。在d+Au碰撞中，发现它超过一个p+p喷流事件和$\rm N_{coll}-1$最小偏差p+p事件的简单和。这些结果的可能解释和它们的影响Au+Au测量进行了讨论。

英文摘要：

Dihadron azimuthal correlation measurements have revealed striking modifications of the jets by the dense medium created in heavy-ion collisions at RHIC. One important question is to what extent the modification can be attributed to cold nuclear matter effects. In this analysis, we carried out a detailed mapping of the correlation patterns using high-statistics RUN8 d+Au minimum bias data. A striking scaling behavior of the jet pair yields is observed at low and intermediate $p_T$. The jet pair yields are found to be enhanced relative to $N_{\rm coll}$ scaled p+p jet pair yields. The nuclear modification factor for jet pair yields, $J_{\rm dAu}$, seems to scale with $p_T^{\rm sum}$= $p_T^a+p_T^b$ (scaler sum), and shows a characteristic Cronin-like enhancement at $p_T^{\rm sum}<$5-7GeV/c. Interestingly, the level of yield modifications is similar between the near- and away-side pairs, and the jet shapes are not modified relative to p+p collisions. The pedestal yield under the jet peak is studied in p+p and d+Au collisions. The pedestal yield in p+p collisions is found to be larger than PYTHIA calculations. In d+Au collisions, it is found to exceed a simple sum of one p+p jet event and $\rm N_{coll}-1$ minimum bias p+p events. The possible interpretation of these results and their implications for Au+Au measurements are discussed.

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