Connecting LHCb to theories of the weak scale

在欧洲核子研究中心大型强子对撞机上，LHCb实验将执行对TeV质量(约为弱玻色子W和Z质量的10-20倍)的新粒子的量子涨落敏感的各种测量。这涉及到所谓的B介子的罕见衰变和相关的物质-反物质不对称。所有解决弱标度(W玻色子和Z玻色子的质量标度)起源的主要提议都预测了TeV质量范围内的粒子，例如超对称性、“大”额外的时空维度、技术色彩和小希格斯理论--通常被称为“新物理”。除了发现希格斯玻色子外，寻找这些粒子是大型强子对撞机实验的主要动机。罕见的B衰变对涉及任何这样的新粒子的量子涨落非常敏感，因为由于各种原因，它们在没有新粒子的情况下被强烈抑制，即在所谓的粒子物理标准模型中。(这就是它们之所以稀有的原因。)因此，他们的测量为“超标准模型”理论的细节提供了非常丰富的信息来源。在LHCb的早期阶段，许多LHCb测量将是可能的，那时所获取的数据量(从技术上讲，是“积分光度”)仍然很小--这在某种程度上领先于ATLAS和CMS的同伴实验，后者专注于直接产生新粒子。英国在LHCb(所有国家中最强大的国家之一)的实验参与程度非常高，但理论活动相对较少。然而，要从数据中读出新物理学的指纹，需要仔细的理论分析，将“已知的”但很难计算的“普通”(标准模型)效应与人们热衷的模式区分开来。这个项目包括系统和精确地应用和进一步发展最先进的方法，基于独占衰变的重夸克展开，到具有最大发现潜力的衰变模式：独有的轻子、半轻子、辐射和两体强子B衰变。因此，它为英国的实验活动提供了有价值和必要的补充，使其能够最大限度地利用这些测量。作为该项目的重要组成部分，其调查人员将定期与英国的实验同事和其他感兴趣的理论家会面，以优化合作和分析策略。

At the CERN LHC, the LHCb experiment will perform a variety of measurements that are sensitive to quantum fluctuations of new particles of TeV mass (about 10-20 times the mass of the weak bosons W and Z) . These involve so-called rare decays of B mesons and related matter-antimatter asymmetries. Particles in the TeV mass range are predicted by all major proposals addressing the origin of the weak scale (mass scale of the W and Z bosons), such as supersymmetry, 'large' extra spacetime dimensions, technicolour, and little higgs theories - generically called 'new physics'. The search for those particles is the main motivation for the LHC experiments, besides the discovery of the Higgs boson. The rare B decays are very sensitive to quantum fluctuations involving any such new particles, because for varying reasons they are strongly suppressed in the absence of new particles, i.e. in what is called the Standard Model of particle physics. (This is what makes them rare.) As such, their measurement provides a very rich source of information on the details of 'beyond-standard model' theories. Many of the LHCb measurements will be possible already in the early stages of the LHCb, when the amount of data taken (technically, 'integrated luminosity') is still small - somewhat of a headstart over the companion experiments ATLAS & CMS, which focus on direct production of new particles. The UK has a very strong experimental involvement in LHCb (one of the strongest of all countries) but comparably very few theoretical activities. To read the fingerprints of the new physics out of the data, however, requires careful theoretical analysis, to separate the 'known', but hard to calculate, 'ordinary' (Standard-Model) effects from the sought-after patterns of what lies beyond. This project involves the systematic and precise application and further development of state-of-the-art methods, based on the heavy-quark expansion for exclusive decays, to the decay modes with the greatest discovery potential: exclusive leptonic, semileptonic, radiative, and two-body hadronic B decays. Thus it provides a valuable and necessary complement to experimental activities in the UK, allowing to make the most of these measurements. As an important part of this project, its investigators will, on a regular basis, meet with experimental UK colleagues and other interested theorists to optimize cooperation and analysis strategies.