Standard Model Phenomenology

汉密尔顿的研究涉及对撞机物理过程的高精度模拟的发展。这些有助于在大型强子对撞机（LHC）上发现和解释新的物理现象。虽然可能不需要精确的模拟来宣布一项发现，例如，如果新的物理现象在平滑分布中表现为一个明显的“凸起”（就像希格斯玻色子一样），在许多新的物理场景中，信号预计会表现为分布形状的微妙扭曲。对标准模型背景的准确理解，受制于所有的实验删减，对于宣称发现或设置排除限制是不可避免的。精确的模拟对于确定被发现的是什么也至关重要。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产生模拟。默认情况下，这种模拟被ATLAS和CMS合作使用，出现在数十份出版物中，面对旨在探测希格斯玻色子性质的测量。自2016年以来，Hamilton与Dasgupta， Salam和Soyez （Panscales）合作，澄清并显着提高了通用蒙特卡罗事件生成器（粒子物理学中使用最广泛的理论工具）的核心，parton shower组件的准确性。经过四年的挑战，在2020年2月，Panscales团队提出了新的最终状态部分阵雨算法，该算法与广泛的独立、专用分析计算完全一致，具有仅次于领先的对数精度；这是过去40年的parton阵雨从未实现过的。索恩的作品是对汉密尔顿作品的补充。它涉及在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），粒子束实际上是由质子内部的基本粒子组成的——夸克和胶子，通常被称为部分子。对标准模型过程的预测，以及潜在的新物理学的预测，都需要在散射过程的能量尺度（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方面，精确地得到强子的部分子组成。索恩是一个已建立的PDF小组MSHT的领导成员，该小组提供了三组部分分布函数（PDF）中的一组，作为大型强子对撞机和其他高能粒子物理实验的实验和理论分析标准。该方法不断得到改进，无论是在理论复杂性方面，还是通过纳入可用的数据，以及由于精度提高或对PDF的不同敏感性，导致进一步的PDF限制。索恩的工作将导致改进PDF确定，为通用提供更新的PDF，他还将调查任何变化的影响。这将有助于更好地理解当前和即将进行的测量，也将影响未来高能粒子物理实验的规划，例如EIC。此外，索恩还是PDF4LHC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），该工作组为在LHC中使用PDF集提供建议，并充当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，为了最大限度地发挥大型强子对撞机的潜力，这一点尤为重要，特别是考虑到目前没有非常明确的新物理信号，但标准模型测试不断出现前所未有的多样性和精度。他们都将提供专业知识来解释任何偏差，这些偏差可能是超越标准模型（BSM）物理学的第一个迹象。

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.