Particle Physics Consolidated Grant from the University of Sheffield: Energy Frontier, Neutrinos, Dark Matter

“宇宙是由什么构成的？为什么？”谢菲尔德的HEP项目旨在解决这一根本问题。这里有两个问题：宇宙中大约五分之一的物质似乎是一种尚未被发现的粒子(暗物质)，剩下的六分之一是所有物质--而不是我们在实验室中制造的50：50的物质-反物质混合物。我们通过两种方式寻找暗物质粒子：在能量前沿，通过在欧洲核子研究中心探测大型强子对撞机的高能质子-质子碰撞产生的新粒子，以及在直接搜索中，试图观察银河系本身中的这些粒子。超对称理论预测了一整套与标准模型(SM)的已知粒子相关但质量更大的粒子，提供了一个候选的暗物质粒子。如果在大型强子对撞机上可以制造出超对称粒子，那么它们应该可以在ATLAS中被探测到。我们的程序专门寻找新的希格斯玻色子，以及与SM夸克和胶子有关的粒子。在ATLAS，我们还研究了包含弱相互作用载流子的SM过程，探索了我们对SM的理解。展望未来，我们正在为ATLAS实验的升级做出必要的工作，以充分利用LHC未来运行中更高的事件率。我们银河系中的大部分物质是暗物质。在LZ实验中，我们寻找暗物质与实验中的Xe原子碰撞并导致它们反冲的证据。这个实验将是有史以来建造的最灵敏的暗物质探测器。了解可能的背景-非暗物质-事件对此至关重要，我们在这一领域拥有世界领先的专业知识。此外，我们正在领导定向暗物质探测器的开发，这将是证明任何候选信号确实来自银河系而不是地球的关键。我们也是唯一参与寻找轴子的英国团队，轴子是另一种可能的暗物质粒子，在大型强子对撞机或标准暗物质实验中无法检测到。为什么宇宙中的物质都是物质，而不是反物质？这个问题的答案肯定在于粒子和反粒子之间的细微差别，这种效应被称为CP破坏。到目前为止观察到的CP破坏效应还不够大，不足以创造我们所看到的宇宙。更多CP破坏的最可能来源是中微子之间的相互作用。一个关键的观察结果是，中微子有质量，不同类型的中微子在飞行中可以互换身份。T2K实验已经对此进行了测量，并检测到了诱人的CP违规迹象。我们计划在这项工作的基础上，在运行实验(T2K和SBND)和设计将具有更高灵敏度的下一代中微子实验方面再接再厉。我们已经开发了工具来帮助中微子界比较结果，并提高我们对中微子如何相互作用的理解。我们对Boulby mine的访问为测试材料和探测器原型提供了一个无价的低背景实验室。最后但同样重要的是，我们寻求将HEP技术应用于工业和解决全球问题。我们正在使用为ATLAS开发的技术，以促进机器人技术的发展，并处理切尔诺贝利等高放射性环境。我们正在设计用于搜索核违禁品和监测火山的Muon探测器。我们的信号处理技术正被应用于改善心脏病患者的医学成像。我们在水切伦科夫中微子探测方面的专门知识正被用于一项旨在监测遵守核不扩散条约情况的实验。所有这些工作都建立在我们的STFC核心计划的基础上，以造福更广泛的世界。

"What is the Universe made of, and why?" Sheffield's HEP programme aims to address this fundamental question. There are two problems here: about 5/6 of the matter in the Universe seems to be an as yet undiscovered particle (dark matter), and the remaining 1/6 is all matter - not the 50:50 matter-antimatter mix we make in laboratories.We search for the dark matter particle in two ways: at the energy frontier, by seeking to detect new particles created by the high-energy proton-proton collisions of the LHC at CERN, and in direct searches, attempting to observe these particles in the Galaxy itself. The theory of supersymmetry, which predicts a whole set of particles related to, but more massive than, the known particles of the Standard Model (SM), offers a candidate dark matter particle. If supersymmetric particles can be made at the LHC, they should be detected in ATLAS. Our programme searches specifically for new Higgs bosons and for particles related to the SM quarks and gluons. At ATLAS, we also study SM processes involving the force carriers of the weak interaction, probing our understanding of the SM. Looking to the future, we are contributing essential work to the upgrade of the ATLAS experiment required to take full advantage of higher event rates in future running of the LHC.Most of the matter in our Galaxy is dark matter. In the LZ experiment, we search for evidence of dark matter colliding with Xe atoms in the experiment and causing them to recoil. This experiment will be the most sensitive dark matter detector ever constructed. Understanding possible background - non-dark-matter - events is critical to this, and we have world leading expertise in this field. In addition, we are leading the development of directional dark matter detectors, which will be vital in proving that any candidate signal really does come from the Galaxy and not the Earth. We are also the only UK group involved in the search for axions: another possible type of dark matter particle which cannot be detected at the LHC or in standard dark matter experiments.Why is the matter in the Universe all matter, not antimatter? The answer to this question must lie in subtle differences between particles and antiparticles, an effect called CP violation. The CP violating effects so far observed are not nearly large enough to create the Universe we see. The most likely source for more CP violation is in the interactions of neutrinos. A key observation is that neutrinos have mass, and that different types of neutrinos can interchange their identities in flight. The T2K experiment has made measurements of this, and has detected tantalising hints of CP violation. We plan to build on this work, both in running experiments (T2K and SBND) and in designing the next generation of neutrino experiments which will have much greater sensitivity. We have developed tools to assist the neutrino community in comparing results and improving our understanding of how neutrinos interact. Our access to Boulby Mine provides an invaluable low-background laboratory for testing materials and detector prototypes.Last but not least, we seek to apply HEP technology to industry and to solving global problems. We are using techniques developed for ATLAS to contribute to the development of robotics and to deal with highly radioactive environments such as Chernobyl. We are designing muon detectors to search for nuclear contraband and monitor volcanoes. Our signal processing techniques are being applied to improving medical imaging for heart patients. Our expertise in water Cherenkov neutrino detection is being exploited in an experiment designed to monitor compliance with nuclear non-proliferation treaties. All of this work builds on our STFC core programme to benefit the wider world.