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arXiv 1806.02697hep-exhep-ph
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用ATLAS探测器测量ZZ的产生和用HERWIG事件generator模拟环诱导过程

Measurements of ZZ production with the ATLAS detector and simulation of loop-induced processes with the HERWIG event generator

Stefan Richter

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PhD thesis (University College London), 252 pages
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摘要：

本论文介绍了实验和理论粒子物理的结果和方法的发展。主要部分显示了在13 TeV质心能量下质子-质子碰撞中产生的$\ell^+\ell^-\ell'^+\ell'^-$（其中$\ell$，$\ell'$是电子或μ子）的测量结果。这些碰撞是由大型强子对撞机在2015年和2016年产生的，并由ATLAS探测器观测到。在对Z玻色子对产生敏感的相空间中，测量了21个观测量的积分截面和微分截面。其中10个直接测量相关的喷气活动。这些测量为粒子物理学的标准模型提供了一个重要的检验。在一个通用的有效场论方法中，直接搜索影响ZZ生产的标准模型之外的效应。未观察到与标准模型预测的显著偏差。在有效场论中，对描述新物理的参数设定了排斥极限。在理论发展中，提出了用Herwig 7事件发生器自动描述循环诱导过程。这些过程只能通过虚拟粒子的量子回路发生。在领先的顺序量子色动力学的初步结果显示生产的希格斯玻色子，一对希格斯玻色子，和四个轻子。希格斯玻色子的结果表明，完整的环诱导描述可以显着偏离常见的近似，其中顶夸克的质量被视为无限大。因此，包括环效应对于获得精确的预测以与大型强子对撞机的测量结果进行比较至关重要。发展走向下一个领导阶描述的任意循环引起的过程。

英文摘要：

This thesis presents results and method developments in both experimental and theoretical particle physics. The main part shows measurements of $\ell^+\ell^-\ell'^+\ell'^-$ production (where $\ell$, $\ell'$ is either an electron or a muon) in proton-proton collisions at 13 TeV centre-of-mass energy. The collisions were produced by the Large Hadron Collider in 2015 and 2016 and observed with the ATLAS detector. In a phase space sensitive to Z boson pair production, the integrated cross section as well as differential cross sections with respect to twenty-one observables are measured. Ten of these directly measure associated jet activity. The measurements provide an important test of the Standard Model of particle physics. A direct search for effects beyond the Standard Model affecting ZZ production is performed in a generic effective field theory approach. No significant deviations from the Standard Model predictions are observed. Exclusion limits are set on the parameters describing new physics in the effective field theory. In theoretical developments, the automated description of loop-induced processes with the Herwig 7 event generator is presented. These are processes that can only occur via a quantum loop of virtual particles. Preliminary results in leading-order quantum chromodynamics are shown for the production of a Higgs boson, of a pair of Higgs bosons, and of four leptons. The Higgs boson results show that the full loop-induced description can deviate significantly from the common approximation where the mass of the top quark is treated as infinitely large. Thus, including loop effects is crucial to obtaining precise predictions to compare to measurements at the Large Hadron Collider. Developments towards a next-to-leading-order description of arbitrary loop-induced processes are shown.

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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