arXiv 0910.18232009-10-09hep-phnucl-th

射流淬火理论预测的系统不确定性

Systematic Uncertainties in Theoretical Predictions of Jet Quenching

W. A. Horowitz, B. A. Cole

备注：: 13 pages, 9 figures
发表信息：: Phys.Rev.C81:024909,2010
DOI：: 10.1103/PhysRevC.81.024909

摘要：

我们发现，目前的辐射能量损失内核从不透明度膨胀显着违反共线近似在其推导。由于只保留了共线性项中的最低阶，基于不透明度展开的模型在计算0 - 5%最中心RHIC碰撞中的pi^0 R_AA时具有约50%的系统不确定性，导致提取的介质密度的系统不确定性约为200%。令人惊讶的是，由于非直观的相干效应，包含德拜屏蔽尺度量级的热胶子质量仅在5%左右的水平上影响R_AA。对于某些观测量，如R_AA，这些不确定性的影响随着喷注能量的增加而减小;对于其他观测量，如辐射胶子的平均数，这种影响与能量无关。我们注意到，不同喷流能量损失模型所报告的介质参数（如qhat）的提取值的差异很可能会落在共线近似系统不确定性范围内;对于介质参数的定量提取或夸克-胶子等离子体介质的硬探针与软模之间弱耦合假设的可能证伪，研究超越了最低阶共线近似。

英文摘要：

We find that the current radiative energy loss kernels obtained from the opacity expansion dramatically violate the collinear approximation used in their derivation. By keeping only the lowest order in collinearity terms, models based on the opacity expansion have ~50% systematic uncertainty in the calculation of pi^0 R_AA in 0-5% most central RHIC collisions resulting in a systematic uncertainty of ~200% in the extracted medium density. Surprisingly, the inclusion of a thermal gluon mass on the order of the Debye screening scale affects R_AA at only about the 5% level due to non-intuitive coherence effects. For some observables such as R_AA, the effect of these uncertainties decreases with increasing jet energy; for others, such as the average number of radiated gluons, the effect is energy independent. We note that it is likely that the differences reported in the extracted values of medium parameters such as qhat by various jet energy loss models will fall within this collinear approximation systematic uncertainty; it is imperative for the quantitative extraction of medium parameters or the possible falsification of the hypothesis of weak coupling between the hard probes and soft modes of the quark gluon plasma medium that future radiative energy loss research push beyond the lowest order collinear approximation.

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