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arXiv 2005.06177hep-exnucl-ex
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用ALICE探测器研究手征磁效应

Search for the Chiral Magnetic Effect with the ALICE detector

Sizar Aziz

摘要:

在非中心重离子碰撞中,不参与相互作用的旁观质子会产生强磁场。这些场的强度允许测试基于QCD的假设性质的效应。所谓的拓扑构型的存在可以产生携带净手性的结构域。与上述磁场耦合,它们可以引起碰撞中产生的粒子的电荷分离。这种电荷分离被称为手性磁效应(CME),可以通过带电粒子的角相关来测量。测量的$γ_{1,1}$相关器,这是敏感的CME,显示为Pb-Pb碰撞在$\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV以及为p-Pb碰撞在$\sqrt{s_{\mathrm{NN}}} = 5.44$ TeV。这些被发现有一个显着的相反的符号和相同符号的电荷对之间的电荷依赖性。这种行为与CME样信号一致。然而,$δ_{1}$相关器,它测量的电荷相关性无关的任何对称平面(即背景),测量的碰撞,也显示出显着的电荷依赖性。这妨碍了对$γ_{1,1}$相关器的清晰解释。新的方法来限制CME贡献的$γ_{1,1}$相关器是必要的。

英文摘要:

In non-central heavy-ion collisions, spectator protons that do not participate in the interaction create strong magnetic fields. The strength of these fields allows testing an effect based on the hypothesized properties of QCD. The presence of so-called topological configurations can give rise to domains that carry net chirality. Coupled with the aforementioned magnetic fields, they may induce a charge separation of the particles generated in the collisions. This charge separation is called the Chiral Magnetic Effect (CME) and can be measured through charged-particle angular correlations. Measurements of the $γ_{1,1}$ correlator, which is sensitive to the CME, are shown for Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV as well as for Xe--Xe collisions at $\sqrt{s_{\mathrm{NN}}} = 5.44$ TeV. These are found to have a significant charge dependence between opposite-sign and same-sign charge pairs. This behavior is consistent with a CME-like signal. However, the $δ_{1}$ correlator, which measures charge correlations unrelated to any symmetry plane (i.e. background), was measured in Xe--Xe collisions and also shows a significant charge dependence. This prevents a clear interpretation of the $γ_{1,1}$ correlator. Novel methods to constrain the CME contribution to the $γ_{1,1}$ correlator are necessary.

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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