Theoretical Studies of Elementary Particles

基本粒子的理论研究

• 批准号: ST/P000789/1
• 负责人: Stephen West
• 金额: $ 6.21万
• 依托单位: Royal Holloway University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FP000789%2F1
• 关键词: Theoretical; Studies; Elementary; Particles

Our ultimate aim is to understand the nature of matter and the most basic processes that drive the universe. One of the most intriguing features of our universe is that we seem to be able to describe much of what happens very well 'theoretically' - using a a set of laws that are written down in the form of a mathematical 'model'. Isaac Newton showed this could be done with objects visible to the naked eye and modern day theorists continue the tradition for particles that have to be created by extreme events, be they cosmic or terrestrial at accelerators like the Large Hadron Collider (LHC) at CERN. The proposed research will address today's major issues in particle theory.The first part of our proposal is to improve predictions of the effects of the strong interactions (QCD) that dominate the production of particles in collisions at the LHC. These collisions create showers of large numbers of known particles which have to be filtered out so that the rare events indicating the presence of a new particle become visible. The discovery of the Higgs boson depended on such calculations; the discovery of further new particles, and the efficient analysis of their properties, will depend on doing those calculations to even higher precision.The Standard Model of the strong, weak and electromagnetic interactions describes most of particle physics with exquisite precision but it has defects. It does not explain dark matter, why the weak interaction scale is relatively light or why there are three generations of quarks and leptons, and it does not contain gravity. Our research will explore models that might remedy these defects and determine what experimental tests would be sensitive to the new 'beyond the Standard Model (BSM)' physics they predict. We will examine supersymmetric field theories, and models with additional space dimensions, to establish whether they contain viable candidates for dark matter without introducing other new physics incompatible with experiment. Superstring theories are a promising candidate for unifying the Standard Model with gravity. However generally they contain an abundance of particles not observed in nature; we will continue our programme to find those consistent with the Standard Model and for the first time calculate the Yukawa couplings that are needed for detailed comparison of light particle masses with experiment. The LHC is also used to collide heavy ions producing a quark-gluon plasma. Understanding the features of this new state of matter is challenging. It reaches thermal equilibrium very quickly and affects non-trivially the behaviour of energetic particles passing through it. The so-called gauge-string duality technique can attack some of these problems but does not apply strictly to real QCD. We propose to develop a composite description that combines this method with other techniques to understand the properties of the real quark-gluon plasma.Extensions of the Standard Model usually contain new particles that cannot be detected directly at the LHC but affect astrophysical and cosmological processes such as inflation and the generation of primordial gravitational waves. An example is the so-called ALP which arises naturally in most string theories and whose presence would be seen in astrophysical X-ray data. An important part of our proposal is to establish in detail the signals from such physics so that we can optimize strategies for detecting them in observational data. In contrast quantum gravity is not yet sufficiently well understood to tension theory against measurement so we will develop methods of computing the large scale properties of the universes in models such as causal dynamical triangulations to determine whether they are plausible candidates to describe quantum gravity.

我们的最终目标是了解物质的本质和驱动宇宙的最基本过程。我们宇宙最有趣的特征之一是，我们似乎能够很好地“理论上”描述发生的事情-使用一套以数学“模型”形式写下的定律。艾萨克·牛顿（Isaac Newton）表明，这可以用肉眼可见的物体来实现，现代理论家继续传统的粒子必须由极端事件产生，无论是宇宙还是地球，都可以在欧洲核子研究中心的大型强子对撞机（LHC）等加速器上产生。这项研究将解决当今粒子理论中的主要问题。我们建议的第一部分是改进对强相互作用（QCD）影响的预测，强相互作用主导了LHC碰撞中粒子的产生。这些碰撞会产生大量已知粒子的簇射，这些粒子必须被过滤掉，以便指示新粒子存在的罕见事件变得可见。希格斯玻色子的发现依赖于这样的计算;更多新粒子的发现以及对它们性质的有效分析，将依赖于更高精度的计算。强、弱和电磁相互作用的标准模型以极高的精度描述了大多数粒子物理学，但它有缺陷。它不能解释暗物质，为什么弱相互作用标度相对较轻，为什么有三代夸克和轻子，而且它不包含引力。我们的研究将探索可能弥补这些缺陷的模型，并确定哪些实验测试对他们预测的新的“超越标准模型（BSM）”物理学敏感。我们将研究超对称场论和具有额外空间维度的模型，以确定它们是否包含暗物质的可行候选者，而不引入其他与实验不相容的新物理。超弦理论是统一标准模型和引力的一个有希望的候选者。然而，一般来说，它们含有大量的在自然界中没有观察到的粒子;我们将继续我们的计划，以找到那些与标准模型一致的粒子，并首次计算汤川耦合，这是将轻粒子质量与实验进行详细比较所必需的。大型强子对撞机也用于碰撞重离子产生夸克胶子等离子体。理解这种新物质状态的特征是具有挑战性的。它很快达到热平衡，并对通过它的高能粒子的行为产生重要影响。所谓的规范弦对偶技术可以解决其中的一些问题，但并不严格适用于真实的QCD。我们建议开发一个复合描述，结合这种方法与其他技术来理解的真实的夸克胶子plasma. Extended的标准模型通常包含新的粒子，不能直接在大型强子对撞机检测到，但影响天体物理和宇宙学过程，如通货膨胀和原始引力波的产生。一个例子是所谓的ALP，它在大多数弦理论中自然产生，在天体物理学的X射线数据中可以看到它的存在。我们建议的一个重要部分是详细建立来自这种物理学的信号，以便我们可以优化在观测数据中检测它们的策略。相比之下，量子引力还没有足够好地理解张力理论对抗测量，所以我们将开发计算模型中宇宙大尺度属性的方法，例如因果动力学三角测量，以确定它们是否是描述量子引力的合理候选者。

项目成果

Can tonne-scale direct detection experiments discover nuclear dark matter?

吨级直接探测实验能否发现核暗物质？

• DOI: 10.1088/1475-7516/2017/10/035
• 发表时间: 2017
• 期刊: Journal of Cosmology and Astroparticle Physics
• 影响因子: 6.4
• 作者: Butcher A

Long-lived particles at the energy frontier: the MATHUSLA physics case

• DOI: 10.1088/1361-6633/ab28d6
• 发表时间: 2018-06
• 期刊: Reports on Progress in Physics
• 影响因子: 18.1
• 作者: D. Curtin;M. Drewes;Matthew McCullough;P. Meade;R. Mohapatra;J. Shelton;B. Shuve;E. Accomando-

Reproductive freeze-in of self-interacting dark matter

自相互作用暗物质的繁殖冻结

• DOI: 10.1103/physrevd.102.083018
• 发表时间: 2020
• 期刊: Physical Review D
• 影响因子: 5
• 作者: March-Russell J