Standard Model Phenomenology

标准模型现象学

• 批准号: ST/X000516/1
• 负责人: Robert Thorne
• 金额: $ 46.94万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FX000516%2F1
• 关键词: Standard; Model; Phenomenology

Hamilton's research concerns the development of high precision simulations of collider physics processes. These facilitate discovery and interpretation of new physics at the Large Hadron Collider (LHC). While precision simulations may not be needed to claim a discovery, e.g. if new physics appears as a clear `bump' in a smooth distribution, (as did the Higgs boson), in many new physics scenarios, signals are expected to manifest as subtle distortions in the shapes of distributions. An accurate understanding of the Standard Model background, subject to all experimental cuts, is then unavoidable for claiming a discovery, or setting exclusion limits. Precision simulations are also essential to determine what it is that has been found. The recently discovered Higgs boson is the prime example of this. Together with collaborators in Milan and Munich, Hamilton developed the world's most accurate simulation of Higgs boson production. This simulation is used, by default, by the ATLAS and CMS collaborations, appearing in dozens of publications, confronted with measurements designed to probe Higgs boson properties. Since 2016 Hamilton has collaborated with Dasgupta, Salam, and Soyez (Panscales), to clarify and significantly improve the accuracy of the core, parton shower, component of general purpose Monte Carlo event generators -- the most widely used theoretical tools in particle physics. After four challenging years, in Feb 2020, the Panscales team presented novel final-state parton shower algorithms in full agreement with a broad range of independent, dedicated, analytic calculations, at next-to-leading logarithmic accuracy; something not previously achieved in 40-years of parton showers.Thorne's work is complementary to that of Hamilton. It involves the precise details of the initial state appearing in hadronic particle collisions. At hadron colliders, e.g. the Large Hadron Collider (LHC), the particle beam is effectively made up of the fundamental particles inside the proton - quarks and gluons, generically known as partons. Predictions for Standard Model processes, and potentially those of new physics, require the precise partonic composition of the hadrons in terms of both the energy scale of the scattering process (e.g., the mass of a particle produced) and the momentum fraction of the incoming proton carried by the parton. Thorne is the lead member of an established PDF group, MSHT, that provides one of the three sets of parton distribution functions (PDFs) used as standard by both the experimental and theoretical analyses at the LHC and other high energy particle physics experiments. The approach is continually improved, both in terms of theoretical sophistication, and by inclusion of data which become available and due to increased precision or different sensitivity to PDFs, lead to further PDF constraints. Thorne's work will lead to improved PDF determination, providing updated PDFs for universal use, and he will also investigate the implications of any changes. This will lead to a better understanding of current and upcoming measurements, and will also influence planning for future high energy particle physics experiments, e.g. the EIC. Additionally, Thorne is a core member of the PDF4LHC working group (a member of the steering committee since the inception, and one of the main drivers and organisers) which provides recommendations for use of PDF sets at the LHC and acts as a direct liason to the LHC, and wider, experimental community.Both Hamilton and Thorne are involved in increasing precision for calculations at particle colliders, which is particularly essential in order maximise the potential of the LHC, particularly given the current situation of no very clear signals of new physics, but continual appearance of unprecedented variety and precision of Standard Model tests. Both will provide expertise in interpreting any deviations which could be the first sign of Beyond the Standard Model (BSM) Physics.

汉密尔顿的研究涉及到对对撞机物理过程进行高精度模拟的发展。这些都有助于在大型强子对撞机（LHC）上发现和解释新物理。虽然可能不需要精确的模拟来宣布一项发现，例如，如果新的物理学在平滑的分布中表现为一个明显的“凸起”（如希格斯玻色子），但在许多新的物理学情景中，信号预计将表现为分布形状的微妙扭曲。准确理解标准模型的背景，服从于所有的实验切割，然后是不可避免的声称一个发现，或设置排除限制。精确的模拟对于确定所发现的是什么也是必不可少的，最近发现的希格斯玻色子就是最好的例子。与米兰和慕尼黑的合作者一起，汉密尔顿开发了世界上最精确的希格斯玻色子生产模拟。默认情况下，ATLAS和CMS合作使用这种模拟，出现在数十种出版物中，面对旨在探测希格斯玻色子性质的测量。自2016年以来，汉密尔顿与Dasgupta，Salam和Soyez（Pancales）合作，以澄清和显着提高核心的准确性，部分子簇射，通用蒙特卡罗事件发生器的组成部分-粒子物理学中最广泛使用的理论工具。经过四年的挑战，2020年2月，Pancales团队提出了新颖的最终状态部分子簇射算法，该算法与广泛的独立，专用，分析计算完全一致，具有领先的对数精度;这是以前在40年的部分子簇射中没有实现的。索恩的工作是对汉密尔顿的补充。它涉及强子粒子碰撞中出现的初始状态的精确细节。在强子对撞机中，例如大型强子对撞机（LHC），粒子束有效地由质子内部的基本粒子组成-夸克和胶子，一般称为部分子。对标准模型过程的预测，以及潜在的新物理学的预测，需要强子在散射过程的能量标度（例如，产生的粒子的质量）和由部分子携带的入射质子的动量分数。索恩是一个已建立的PDF组MSHT的领导成员，该小组提供了三套部分子分布函数（PDF）之一，这些部分子分布函数被LHC和其他高能粒子物理实验的实验和理论分析用作标准。该方法不断改进，无论是在理论上的复杂性，并通过纳入数据变得可用，并由于增加的精度或不同的敏感性PDF，导致进一步的PDF约束。Thorne的工作将改进PDF的确定，提供更新的PDF供普遍使用，他还将调查任何变化的影响。这将导致更好地理解当前和即将到来的测量，也将影响未来高能粒子物理实验的规划，例如EIC。此外，索恩是PDF 4LHC工作组的核心成员（自成立以来一直是指导委员会的成员，也是主要的推动者和组织者之一），为LHC使用PDF集提供建议，并作为LHC和更广泛的实验社区的直接联络人。汉密尔顿和索恩都参与了提高粒子对撞机计算精度的工作，这对于最大限度地发挥大型强子对撞机的潜力尤其重要，特别是考虑到目前没有非常明确的新物理信号，但标准模型测试的前所未有的多样性和精度不断出现。两者都将提供解释任何偏差的专业知识，这些偏差可能是超越标准模型（BSM）物理学的第一个迹象。