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arXiv 2002.05503hep-ph
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LHC上Pb+Pb碰撞中$γγ\to τ^+ τ^-$反应中$τ$轻子的反常电磁矩

Anomalous electromagnetic moments of $τ$ lepton in $γγ\to τ^+ τ^-$ reaction in Pb+Pb collisions at the LHC

Mateusz Dyndal, Mariola Klusek-Gawenda, Matthias Schott, Antoni Szczurek

摘要:

本文讨论了LHC能区Pb+Pb超周边碰撞中的$γγ\to τ^+ τ^-$过程对$τ$轻子反常磁矩($a_τ$)和反常电磁矩($d_τ$)的敏感性。我们推导出相应的截面折叠的重离子光子通量的基本截面,并考虑半轻子衰变的$τ$轻子在基准体积的ATLAS和CMS探测器。我们提出了预测的总截面和微分截面,并为比率$γγ\to e^+ e^- (μ^+ μ^-$)过程。当在大型强子对撞机上对$a_τ$进行精确测量时,这些比值可以消除理论和实验的不确定性。与现有Pb+Pb数据集相比,$a_τ$的预期限制被发现比当前最佳实验限制好了两倍,并且可以在高亮度LHC上进一步提高另一个两倍。

英文摘要:

We discuss the sensitivity of the $γγ\to τ^+ τ^-$ process in ultraperipheral Pb+Pb collisions on the anomalous magnetic ($a_τ$) and electric ($d_τ$) moments of $τ$ lepton at LHC energies. We derive the corresponding cross sections by folding the elementary cross section with the heavy-ion photon fluxes and considering semi-leptonic decays of both $τ$ leptons in the fiducial volume of ATLAS and CMS detectors. We present predictions for total and differential cross sections, and for the ratios to $γγ\to e^+ e^- (μ^+ μ^-$) process. These ratios allow to cancel theoretical and experimental uncertainties when performing precision measurement of $a_τ$ at the LHC. The expected limits on $a_τ$ with existing Pb+Pb dataset are found to be better by a factor of two comparing to current best experimental limits and can be further improved by another factor of two at High Luminosity LHC.

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