Birmingham Experimental Particle Physics Consolidated Grant

一般来说，粒子物理学，特别是通过希格斯玻色子来理解质量起源的探索，是当前公众意识的主流。随着欧洲核子研究中心（CERN）的大型强子对撞机（LHC）越来越强大，该领域从未有过比这更令人兴奋的时刻。伯明翰大学参与了四个大型强子对撞机实验中的三个，以及一个使用固定目标的较小规模的欧洲核子研究中心实验，这在英国大学中是独一无二的。我们研究在这些实验中观察到的粒子碰撞和衰变，目的是确定物质的最终结构和自然力。我们最大的活动是ATLAS合作，小组成员Dave Charlton是副发言人。ATLAS的设计目的是在实验室达到的最高能量下研究粒子物理学的广泛方面，首要任务是寻找希格斯玻色子。每秒发生的碰撞多达10亿次，但只有大约400次可以被永久记录和分析。我们的ATLAS小组建造、维护和操作ATLAS“触发器”的一个主要部分，即实验的电子大脑，它的任务是选择有趣的事件，如候选希格斯玻色子，并在碰撞发生后的百万分之一秒内将数据速率降低1000倍。我们也非常积极地分析结果数据，有一个特别强大的团队研究希格斯粒子的搜索，另一个团队研究顶夸克的产生和衰变。顶夸克是已知粒子中最重的，对以前未知的物理现象具有极高的灵敏度。在大型强子对撞机时代之前，顶夸克样本很小，而ATLAS已经收集了近10万个事件。大型强子对撞机预计将运行到2030年左右，但在其生命周期中需要几次停机，届时加速器和探测器将得到改进。我们已经在努力升级我们的触发器，以提高其选择能力，使其能够应对预计从2018年开始增加的碰撞率。展望未来，我们将利用我们在硅基探测器上直接结合电子器件的专业知识，为2022年左右需要的探测器内部部件的替换做出重大贡献。除了ATLAS之外，我们的第二个关键活动领域是了解重夸克的复杂衰变。在LHCb实验中，我们通过寻找b夸克和反夸克的衰变特征之间的微小差异，来研究宇宙物质-反物质不对称的起源。我们在2011年3月加入LHCb，承担了模拟探测器和使用全球计算网格执行分布式分析的基本技术责任。在接下来的几年里，我们的目标是进一步发展这些角色以及我们的物理分析，目前主要集中在b味粒子的罕见衰变上。我们的NA62小组通过研究奇异粒子的衰变来寻找新的物理现象，比如超对称。下一个拨款期对NA62至关重要，因为它需要数据来研究一种超罕见的过程，在这种过程中，一种奇怪的粒子，即介子，衰变产生一个介子，它由轻夸克和两个中微子组成。这一过程每100亿个k介子衰变中只发生一次，预计在两年的时间里只会发生80次。任何关于更大速率的暗示都将是新物理学的明确迹象。该小组正在领导NA62探测器建设和数据分析的几个方面。最后，该小组包括未来可能的“大型强子对撞机”项目的核心支持者，该项目将使电子与大型强子对撞机的质子束碰撞，以及长期存在的线性电子-正电子对撞机项目。我们将继续担任这些领导角色，并准备在机会出现时加强我们的参与。

Particle physics in general, and particularly the quest to understand the origins of mass through the Higgs boson, are in the mainstream of current public consciousness. With the CERN Large Hadron Collider (LHC) going from strength to strength, there has never been a more exciting time in the field. Birmingham is unique among UK universities in being involved in three of the four main LHC experiments, as well as a smaller scale CERN experiment which uses a fixed target. We study the particle collisions and decays observed in these experiments with the aim of determining the ultimate structure of matter and the forces of nature.Our biggest activity is with the ATLAS collaboration, for which group member Dave Charlton is the deputy spokesperson. ATLAS is designed to study wide-ranging aspects of particle physics at the highest energies ever reached in the laboratory, the first priority being the search for the Higgs boson. From up to a billion collisions taking place per second, only around 400 can be permanently recorded and analysed. Our ATLAS group built, maintains and operates a major part of the ATLAS `trigger', the electronic brain of the experiment, which has the task of selecting interesting events such as candidate Higgs bosons, and reducing the data rate by a factor of 1000 within two millionths of a second after collisions take place. We are also very active in analysing the resulting data, with a particularly strong team working on Higgs searches and another investigating the production and decays of top quarks. Being the heaviest of the known particles, top quarks offer excellent sensitivity to previously unknown physics. Whilst top quark samples were small before the LHC era, ATLAS has already collected approaching 100,000 events.The LHC is expected to operate until around 2030, but will need several shut-down periods during its lifetime, when the accelerator and detectors will be improved. We are already working towards an upgrade of our trigger to improve its selection capabilities and enable it to cope with the increased collision rates expected from 2018. Looking even further to the future, we will use our expertise in the bonding of electronics directly onto silicon-based detectors to make major contributions to a replacement for the inner part of the detector, which will be needed in around 2022.Beyond ATLAS, our second key area of activity is in understanding the complex decays of heavy quarks. At the LHCb experiment, we are investigating the origins of the matter-antimatter asymmetry of the Universe by searching for tiny differences between the decay characteristics of b quarks and their antiquarks. We are relative newcomers to LHCb, having joined in March 2011 and taken on essential technical responsibilities in simulating the detector and enabling the use of the world-wide computing grid to perform distributed analysis. In the next few years, we aim to further develop these roles as well as our physics analyses, which are currently focused on rare decays of b flavoured particles. Our NA62 group studies the decays of strange particles to search for new physics such as supersymmetry. The next grant period will be crucial for NA62, as it takes data to study an ultra rare process in which a strange particle, the kaon, decays to produce a pion, which is made of light quarks, and two neutrinos. This process occurs only once in every 10 billion kaon decays and only 80 events are expected in a two year run. Any hint of a larger rate would be a very clear indication of new physics. The group is leading several aspects of NA62 detector construction and data analysis. Finally, the group contains central proponents of a possible future `LHeC' project to collide electrons with the LHC proton beam, as well as the long-standing linear electron-positron collider project. We will continue in these leadership roles and be ready to step up our involvement should the opportunity arise.