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arXiv 2005.02320hep-ph
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重离子碰撞中喷流背景涨落的模型研究

Model studies of fluctuations in the background for jets in heavy ion collisions

Charles Hughes, Antonio Carlos Oliveira Da Silva, Christine Nattrass

发表信息：
Phys. Rev. C 106, 2022, 044915
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摘要：

高能重离子碰撞中产生的喷流被夸克-胶子等离子体淬灭。这些喷流的测量受到用于抑制和减去大的波动背景的方法以及这些方法中固有的假设的影响。我们比较的背景测量的Pb+Pb碰撞在$\sqrt{s_{NN}}$ = 2.76 TeV的ALICE合作$\underline{(B. Abelev \textit{et al.}, J. High Energy Phys. \mathbf{2012}, 053)}$的计算在TennGen（数据驱动的随机背景发生器）和PYTHIA Angantyr。详细了解这些波动的宽度对于减少由于展开和将测量扩展到较低动量和较大分辨率参数而产生的不确定性非常重要。TennGen中随机锥的能量标准偏差与ALICE论文中的预测形式近似一致，偏差为1- 6%。在Angantyr随机锥的能量标准偏差超过相同的预测约13%。两个模型中的偏差可以通过以下假设来解释：在预测的推导中，单粒子$d^2N/dy$ $dp_T$是伽马分布，而模型使用不同的分布。这表明，模型比较对背景的处理可能很敏感。我们证明，用于消除喷流背景波动的展开方法会影响模型和数据$\textit{even in the absence of detector effects}$之间的比较。我们的研究结果表明，需要更仔细地考虑比较模拟和数据的方法。

英文摘要：

Jets produced in high energy heavy ion collisions are quenched by the quark gluon plasma. Measurements of these jets are influenced by the methods used to suppress and subtract the large, fluctuating background and the assumptions inherent in these methods. We compare the measurements of the background in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV by the ALICE Collaboration $\underline{(B. Abelev \textit{et al.}, J. High Energy Phys. \mathbf{2012}, 053)}$ to calculations in TennGen (a data-driven random background generator) and PYTHIA Angantyr. A detailed understanding of the width of these fluctuations is important for reducing uncertainties due to unfolding and extending measurements to lower momenta and larger resolution parameters. The standard deviation of the energy in random cones in TennGen is approximately in agreement with the form predicted in the ALICE paper, with deviations of 1--6%. The standard deviation of energy in random cones in Angantyr exceeds the same predictions by approximately 13%. Deviations in both models can be explained by the assumption that the single-particle $d^2N/dy$ $dp_T$ is a gamma distribution in the derivation of the prediction, whereas the model uses a different distribution. This indicates that model comparisons are potentially sensitive to the treatment of the background. We demonstrate that unfolding methods used to remove background fluctuations from jets can affect the comparisons between models and data, $\textit{even in the absence of detector effects}$. Our findings suggest the need to more carefully consider methods for comparing simulations and data.

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