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arXiv 2409.12641nucl-exhep-ex
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在质心每核子对能量为 $\sqrt{s_{\rm NN}}=5.02$ TeV 的 pp 和 Pb$-$Pb 碰撞中测量包含孤立光子的产生截面

Measurement of the inclusive isolated-photon production cross section in pp and Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV

ALICE Collaboration

AI总结:

ALICE 合作组在 $\sqrt{s_{\rm NN}}=5.02$ TeV 的 pp 和 Pb$-$Pb 碰撞中测量了包含孤立光子的产生截面,发现核修正因子与 1 一致,并与微扰 QCD 计算及 CMS 实验结果相符。

摘要:

CERN LHC 的 ALICE Collaboration 测量了在每核子对质心能量 $\sqrt{s_{\rm NN}}=5.02$ TeV 下,不同中心度区间的 Pb$-$Pb 碰撞以及 pp 碰撞中,中心快度下包含孤立光子的产生截面随光子横动量($p_{\rm T}^γ$)的函数关系。光子横动量范围在 10-14 至 40-140 GeV/$c$ 之间,具体取决于碰撞系统和 Pb$-$Pb 碰撞的中心度类别。该结果比 ATLAS 和 CMS 实验在相同碰撞能量下已发表的结果延伸至更低的 $p_{\rm T}^γ$。所覆盖的赝快度范围为 $|η^γ| <0.67$。孤立选择基于在半径 $R=0.2$ 和 $0.4$ 的锥体内,带电粒子孤立动量阈值 $p_{\rm T}^{\rm iso,~ch} = 1.5$ GeV/$c$。计算得到的核修正因子在所有中心度类别中均与 1 一致,并且与 HG-PYTHIA 模型一致,该模型描述了影响 Pb$-$Pb 碰撞外围中心度测定的事件选择和几何偏差。该测量与次领头阶微扰 QCD 计算以及 CMS 实验的孤立光子和 Z$^0$ 玻色子测量结果进行了比较,发现均一致。

英文摘要:

The ALICE Collaboration at the CERN LHC has measured the inclusive production cross section of isolated photons at midrapidity as a function of the photon transverse momentum ($p_{\rm T}^γ$), in Pb$-$Pb collisions in different centrality intervals, and in pp collisions, at centre-of-momentum energy per nucleon pair of $\sqrt{s_{\rm NN}}=5.02$ TeV. The photon transverse momentum range is between 10-14 and 40-140 GeV/$c$, depending on the collision system and on the Pb$-$Pb centrality class. The result extends to lower $p_{\rm T}^γ$ than previously published results by the ATLAS and CMS experiments at the same collision energy. The covered pseudorapidity range is $|η^γ| <0.67$. The isolation selection is based on a charged particle isolation momentum threshold $p_{\rm T}^{\rm iso,~ch} = 1.5$ GeV/$c$ within a cone of radii $R=0.2$ and $0.4$. The nuclear modification factor is calculated and found to be consistent with unity in all centrality classes, and also consistent with the HG-PYTHIA model, which describes the event selection and geometry biases that affect the centrality determination in peripheral Pb$-$Pb collisions. The measurement is compared to next-to-leading order perturbative QCD calculations and to the measurements of isolated photons and Z$^0$ bosons from the CMS experiment, which are all found to be in agreement.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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