Measurement of the ttH production cross-section in the H to bb decay channel

H 至 bb 衰变通道中 ttH 生产横截面的测量

• 批准号: 2604920
• 金额: --
• 依托单位: University of Glasgow
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2604920
• 关键词: Measurement; ttH; production; cross; section

This PhD project is defined within the ATLAS collaboration, working on identifying Higgs bosons produced in association with a top-quark pair. This is one of the most complicated analyses performed by the ATLAS collaboration due the low signal and high background rates, coupled with the difficulties which come in associating uncertainties to a background process which is still being understood by the experimental and theoretical communities, namely top-quark pairs produced in association with heavy-flavour hadrons.There will be opportunities to develop the next round of the ttH analysis based on Run-3 data. Run 3 will more than double the current dataset. The larger dataset allows increasingly differential measurements that are powerful for constraining potential Beyond Standard Model (BSM) effects through Higgs Effective Field Theories, while also challenging the theory predictions and requiring improved modelling to reduce the systematic limitations. There will be scope to develop new machine learning methods as well as to incorporate ongoing ATLAS development that these analysis techniques and algorithms are based on. This could improve the performance of these algorithms as new b-tagging algorithms and jet objects are being developed.The ttH process where the Higgs decays into b-quarks offers the highest statistics to probe the Higgs-top coupling. The analysis will exploit these events to probe the ttH process at high pT, where there is high sensitivity to BSM effects. The focus will be on two areas: first improvements to the selection of high pT events, leading to so-called boosted events, and secondly by incorporating improved modelling for the dominant top-quark pair background. Working within the analysis team, the PhD student will improve the multivariate selection that is used to select boosted Higgs bosons. The student will also develop full reconstruction for the boosted ttH(bb) channel. This will allow differential measurements of variables involving the top-quark four-vectors that have increased sensitivity to a possible CP-violating Higgs-top coupling in the boosted regime. The combination of these two work areas will result in differential measurements of ttH production from Run-2+3 data that will significantly improve on the Run-2 results and provide tight constraints on BSM contributions to the Higgs-top coupling.Potential beneficiaries include:1. Particle physicists and others with a direct interest in fundamental particles, within and beyond the Standard Model.2. Users of large-scale computing resources in many fields of science.3. Physics graduates gaining from postgraduate teaching and projects as well as from PhD training within the group.4. Firms employing our PhD graduates who will benefit from their leading-edge skills and ability to work in challenging international environments.

这个博士项目是在ATLAS合作中定义的，致力于识别与顶夸克对相关的希格斯玻色子。这是由ATLAS合作进行的最复杂的分析之一，由于低信号和高背景速率，加上将不确定性与背景过程相关联的困难，该背景过程仍被实验和理论界所理解，即顶夸克对产生于重-将有机会基于运行-3数据开发下一轮ttH分析。运行3将使当前数据集增加一倍以上。更大的数据集允许越来越多的差分测量，这些测量对于通过希格斯有效场理论约束潜在的超越标准模型（BSM）效应是强大的，同时也挑战了理论预测，并需要改进建模以减少系统限制。我们将有机会开发新的机器学习方法，并将这些分析技术和算法所基于的正在进行的ATLAS开发纳入其中。随着新的b标记算法和喷流对象的开发，这可以提高这些算法的性能。希格斯衰变为b夸克的ttH过程提供了最高的统计数据来探测希格斯-顶耦合。该分析将利用这些事件来探测高pT下的ttH过程，其中对BSM效应具有高灵敏度。重点将放在两个领域：首先是改进高pT事件的选择，导致所谓的助推事件，其次是通过纳入主要顶夸克对背景的改进建模。在分析团队中工作，博士生将改进用于选择增强希格斯玻色子的多元选择。学生还将为增强的ttH（bb）通道开发完整的重建。这将允许差分测量的变量，涉及顶夸克四矢量，增加了敏感性，可能CP违反希格斯顶耦合在助推制度。这两个工作领域的组合将导致来自运行2+3数据的ttH产生的差分测量，这将显著改善运行2的结果，并对BSM对Higgs-top耦合的贡献提供严格的限制。粒子物理学家和其他对基本粒子有直接兴趣的人，在标准模型之内和之外。许多科学领域的大规模计算资源的用户。物理学毕业生从研究生教学和项目中获得，以及从集团内的博士培训中获得。公司雇用我们的博士毕业生谁将受益于他们的前沿技能和能力，在具有挑战性的国际环境中工作。