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

“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。我们还领导了一个最近资助的英国项目，寻找轴子：另一种可能的暗物质粒子，在大型强子对撞机或标准的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CP违反的有力证据，但还没有确定的证据。我们计划在运行实验(T2K和SBND)和设计下一代中微子实验(如Hyper-K和Dune)的基础上继续这项工作，这些实验将具有更高的灵敏度。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矿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。中微子在天体物理学中也很重要。我们在研究Super-K和Hyper-K中的超新星中微子方面发挥了主导作用，并开发了一个开源工具来帮助该领域的实验人员实现新的理论模型。这项工作可能有助于解释重元素是如何在超新星中产生并在宇宙中传播的。我们正在继续我们与LAR探测器的研发工作，以进行未来的实验。最后，我们寻求将HEP技术应用于工业和解决全球问题。我们正在设计Muon探测器，以对核废料进行成像，检查铁路和公路隧道的完整性，并监控民用基础设施。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核不扩散条约遵守情况的实验，我们在数据分析方面的专门知识正被用于一个帮助气象局定位闪电和追踪严重风暴的项目。所有这一切都建立在我们STFC核心计划的基础上，以造福于更广泛的世界。

"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. We are also leading a recently funded UK project searching 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 strong, but not yet definitive, evidence 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 (such as Hyper-K and DUNE) 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.Neutrinos are also important in astrophysics. We play a leading role in efforts to study supernova neutrinos in Super-K and Hyper-K, and have produced an open-source tool to help experimenters in this field implement new theoretical models. This work may help explain how heavy elements are created in supernovae and disseminated through the Universe. We are continuing our R&D work with LAr detectors for future experiments.Finally, we seek to apply HEP technology to industry and to solving global problems. We are designing muon detectors to image nuclear waste, check the integrity of rail and road tunnels, and monitor civil infrastructure. Our expertise in water Cherenkov neutrino detection is being exploited in an experiment designed to monitor compliance with nuclear non-proliferation treaties, and our expertise in data analysis in a project to help the Met Office locate lightning strikes and track severe storms. All of this builds on our STFC core programme to benefit the wider world.