arXiv 0901.13932009-01-10nucl-ex

PHENIX中的双粒子直接光子-喷注关联测量

Two-particle Direct Photon-Jet Correlation Measurements in PHENIX

Justin Frantz

摘要：

本文给出了sqrtsNN= 200 GeV的$p+p$和$Au+Au$碰撞中各种2粒子直接光子-强子关联强度和产额。直接光子喷注关联的直接光子强子对的每次触发产额是通过统计扣除包含光子强子样本的衰变光子对得到的。利用蒙特卡罗方法计算了$π^0$ -强子的衰变动力学和探测器响应，得到了衰变光子的触发产额。假设抑制是几乎独立的Pt使用一个特定的平均计划，我们发现一个平均比例的Au+Au到p+p每触发光子产额，$I_{AA}$，符合单粒子抑制水平Raa，这可以解释为一个定性确认的基本几何图片喷流抑制在RHIC。在$p+p$中逐事件光子隔离切割的应用导致我们迄今为止最高精度的测量，并且允许对基线碎裂函数$D(z)$以及与表观本征$k_T$或原始碰撞部分子的非零横向动量成比例的变量\pout进行精确研究。与模型相关的提取方法，平均$sqrt(<k_T^2>)$在这个质心的能量在p+p被发现是在3 GeV附近，与双强子（双喷流）的相关性分析。这一点以及孤立产率的精度提高，保证了与各种喷流能量损失模型中使用的基线微扰QCD（pQCD）计算的进一步比较。最后，我们提出了一个独特的直接测量单提示光子射流破碎。

英文摘要：

Various 2-particle direct photon-hadron correlation strengths and yields in $p+p$ and $Au+Au$ collisions at sqrtsNN= 200 GeV are presented. The per-trigger yield of direct photon hadron pairs from direct-photon-jet correlations in is obtained by a statistical subtraction of the decay photon pairs from inclusive photon-hadron sample. The decay photon per-trigger yields are estimated from the measured $π^0$-hadron by means of a Monte Carlo based calculation which takes into account decay kinematics and detector response. Under the assumption that the suppression is nearly pt independent using a specific averaging scheme, we find an average ratio of Au+Au to p+p per-trigger photon yields, $I_{AA}$, consistent with the single particle suppression level Raa, which can be interpreted as a qualitative confirmation of the basic geometrical picture of jet suppression at RHIC. The application of the event by event photon isolation cuts in $p+p$ results our highest precision measurement yet, and allows for precision studies of the baseline fragmentation function $D(z)$, and well as a variable \pout which is proportional to the apparent intrinsic $k_T$, or non-zero transverse momentum of the original collision partons. With a model dependent extraction method, the average $sqrt(<k_T^2>)$ at this center of mass energy in p+p is found to be in the vicinity of 3 GeV, consistent with analysis of di-hadron (di-jet) correlations. This and the improved precision in the isolated yields warrant further comparison with the baseline perturbative QCD (pQCD) calculations used in the various models of jet energy loss. Finally, we present a unique direct measurement of single prompt photons from jet fragmentation.

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英文摘要：

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