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

这个学生将致力于在重口味观测中寻找新的物理，并致力于火炬项目的发展。TORCH(内反射切伦科夫光的时间)是一种新型的飞行时间探测器，用于识别带电粒子。这项应用是对LHCb实验的升级，它将补充低动量下的粒子识别。为了在10m的标称飞行路径上实现介子和介子之间高达10GeV/c的三西格玛间隔，给出每道约30个光子，每道约15ps的时间分辨率是必需的。这位学生将在66x125x1 cm^3区域的一个半尺寸火炬模块上工作。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图案以分离介子和质子，努力达到所需的每光子70ps的计时精度和大约100微米的空间分辨率。他将在实验室中测试工业制造的微通道板探测器(MCP-PMT)，这种探测器使用一种新的电荷分割技术，由牛津大学开发的定制电子学读出。这个项目对于D·Phil的学生来说是一个难得的机会，因为它引导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。这个学生的物理课程将集中在用于探索新的物理效应的罕见衰变上，因为有有趣的证据表明，LHCb在涉及轻子的终态中产生了无法解释的效应。目前正在考虑几种衰败模式，第一年项目的一个重要部分将是评估这些途径的可行性。新的焦点将放在涉及强子和轻子的混合物的终态上，这些强子和轻子的味道组态在SM中被高度抑制或禁止。例如，一个关键的想法是使用具有两个不同味道的轻子的终态，对于这种轻子，SM中不存在任何机制，但这是轻夸克模型的标志。这项工作将评估LHCb中对这些特征的潜在敏感性，以及LHCb的升级。通过从B、J/psi或Upsilon衰变中寻找u-tau终态，也将考虑无强子的轻子味破坏。最后，沿着相同的主题，学生将进行一次公元前衰变中的弱电企鹅的搜索。在我们小组发现对BC介子的强子衰变有贡献的大的非树振幅之后，人们对寻找增强的弱电企鹅很感兴趣。

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.