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？”谢菲尔德大学的HEP项目旨在解决这个基本问题。这里有两个问题：宇宙中大约5/6的物质似乎是一种尚未发现的粒子（暗物质），剩下的1/6都是物质——而不是我们在实验室里制造的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，通过寻找由欧洲核子研究中心（CERN）的大型强子对撞机（LHC）的高能质子-质子碰撞产生的新粒子，以及直接搜索，试图观察银河系本身的这些粒子。超对称理论预测了一整套与标准模型（SM）中已知粒子相关但质量更大的粒子，它提供了一种候选暗物质粒子。如果超对称粒子可以在大型强子对撞机中制造出来，那么它们应该可以在ATLAS中检测到。我们的项目专门搜索新的希格斯玻色子以及与SM夸克和胶子相关的粒子。在ATLAS，我们还研究了涉及弱相互作用的力载流子的SM过程，探索了我们对SM的理解。展望未来，我们正在为ATLAS实验的升级做出重要贡献，以充分利用大型强子对撞机未来运行中更高的事件率。我们银河系中的大部分物质都是暗物质。在LZ实验中，我们在实验中寻找暗物质与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最灵敏的暗物质探测器。了解可能的背景-非暗物质-事件对这一点至关重要，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，这对于证明任何候选信号确实来自银河系而不是地球至关重要。我们也是唯一一个参与寻找轴子的英国小组：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？这个问题的答案一定在于粒子和反粒子之间的细微差别，一种被称为CP破坏的效应。到目前为止观测到的CP违反效应还不足以形成我们所看到的宇宙。更多CP违逆最有可能的来源是中微子的相互作用。一个关键的观察是中微子有质量，不同类型的中微子可以在飞行中交换它们的身份。T2K实验对此进行了测量，并发现了CP违反的诱人迹象。我们计划在这项工作的基础上，在运行实验（T2K和SBND）和设计下一代灵敏度更高的中微子实验。我们已经开发了工具来帮助中微子社区比较结果和提高我们对中微子如何相互作用的理解。我们对博尔比矿的访问为测试材料和探测器原型提供了宝贵的低背景实验室。最后但并非最不重要的是，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开发的技术来促进机器人技术的发展，并处理像切尔诺贝利这样的高放射性环境。我们正在设计μ子探测器，以搜索核走私和监测火山。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业知识正在一项旨在监测遵守核不扩散条约的实验中得到利用。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.