The search for lepton flavour violation in very rare decays of heavy mesons and the prototyping of the TORCH sub-detector

这个学生将致力于寻找新的物理学在重味观测和火炬项目的发展。TORCH（Time Of Internal Reflected Cherenkov Light）是一种用于识别带电粒子的新型飞行时间探测器。该应用程序是LHCb实验的升级，它将补充低动量下的粒子识别。为了在10米的标称飞行路径上达到10 GeV/c的π介子和K介子之间的3 σ分离，需要每个轨道约15 ps的时间分辨率，假设每个轨道约30个光子。学生将在面积为66x125x1cm^3的半尺寸TORCH模块原型上工作。他将在欧洲核子研究中心的PS测试束上获取数据，然后分析复杂的光子模式以分离π介子和质子，努力达到所需的每光子70 ps的计时精度和约100微米的空间分辨率。他将在实验室测试工业制造的微通道板探测器（MCP-PMT），该探测器使用一种新颖的电荷分离技术，由牛津大学开发的定制电子设备读出。该项目对于菲尔博士的学生来说是一个独特的机会，因为它引领了通过在事件重建中使用亚纳秒计时信息来处理高亮度的概念。该学生的物理主题将集中在罕见的衰变上，用于根据LHCb在涉及轻子的最终状态下无法解释的效应的有趣证据来探索新的物理效应。目前正在考虑几种衰减模式，第一年项目的一个重要部分将是评估这些途径的可行性。新的重点将是涉及强子和轻子的混合物的味道配置，高度抑制，或禁止在SM的最终状态。一个关键的想法将是使用具有两个不同味道的轻子的终态，例如，在SM中不存在这种机制，但这是轻夸克模型的标志。这项工作将评估LHCb对这些特征的潜在敏感性，以及LHCb的升级。通过从B、J/psi或Upperdance衰变中寻找μ-τ末态，也将考虑没有强子的轻子味破坏。最后，也是沿着相同的主题，学生将在Bc衰变中寻找电弱企鹅。继我们小组发现的大非树振幅的强子衰变的Bc介子，它是感兴趣的搜索增强的电弱企鹅。

This student will work on searches for new physics in heavy flavour observables and on the development of the TORCH project. TORCH (Time Of internally Reflected CHerenkov light) is a novel Time-of-Flight detector to identify charged particles. The application is for an upgrade of the LHCb experiment, where it would supplement the particle identification at low momentum. In order to reach three sigma separation between pions and kaons up to 10 GeV/c over a nominal flight path of 10m, a time resolution of ~15ps per track is required, given ~30 photons per track. The student will work on a prototype half-sized TORCH module of area 66x125x1cm^3. He will take data at the PS testbeam at CERN and then analyse the complex photon patterns to separate pions and protons, striving to reach the required timing accuracy of 70ps per photon and a spatial resolution of around a 100 microns. He will test in the laboratory industry-fabricated micro-channel plate detectors (MCP-PMTs) which use a novel charge division technique, read out by customised electronics which have been developed in Oxford. This project is unique opportunity for the D.Phil student as it is leads the concept of dealing with high luminosities through the use of sub-nanosecond timing information in event reconstruction.The physics topics for this student will concentrate on rare decays used to probe for new physics effects in the light of the intriguing evidence of unexplained effects from LHCb in final states involving leptons. Several decay modes are currently being considered and an important part of the first year project will be to evaluate the viability of these avenues. The novel focus will be on final states involving a mixture of hadrons and leptons in flavour configurations that are highly suppressed, or forbidden in the SM. A key idea will be using final states with two lepton of different flavour for which no mechanism exists in the the SM but is a hallmark of leptoquark models, for example. The work will evaluate the potential sensitivity to these signatures in LHCb, and the LHCb upgrade. Consideration will also be given to lepton flavour violation without hadrons by looking for the mu-tau final state from B, J/psi or Upsilon decays. Finally, and along the same theme, the student will conduct a search for electroweak penguins in Bc decays. Following our group's discovery of large non-tree amplitudes contributing to hadronic decays of the Bc meson, it is of interest to search for enhanced electroweak penguins.