FOR 5199: Searching for charged lepton flavour violation with the Mu3e experiment

该项目旨在为所有参与MU3E实验的德国团体(海德堡、卡尔斯鲁厄和美因茨)建立一个DFG研究小组。通过MU3E实验，我们的目标是寻找最终灵敏度低于B(μ→eee)和lt；1E-16的稀有衰变μ→eee。这种衰变在粒子物理学的扩展标准模型(SM)中是允许的(对于大质量中微子)，尽管预测了&lt；&lt；1E-56的极小衰减率，这就是为什么这种衰变在SM内几乎看不到。轻子味道破坏(LFV)衰变的发现将因此证明SM之外存在新的物理。SM之外的各种模型预测了LFV过程。这些理论包括超对称性、小希格斯模型、具有额外(压缩)空间维度的模型或大统一理论。因此，世界各地的几个小组正在准备不同的实验来寻找LFV过程也就不足为奇了。目前对衰变μ→eee的实验排除极限来自于30多年前进行的SINDRUM实验，并且是B(μ→eee)&lt；1E-12(90%置信度)。因此，Mu3e实验最终寻求将灵敏度提高四个数量级。在第一阶段(第一阶段)，Mu3e实验将在Paul-Scherrer研究所(PSI，瑞士)的PiE5光束线上进行，该研究所提供纯高强度的Muon光束。对于第一阶段，在大约3年的运行时间后，灵敏度预计为B(μ→eee)&lt；5e-15。第二阶段将需要一条新的、甚至更强的光束线，目前正处于规划阶段。在拟议的研究单位内，德国Mu3e小组计划建立、委托和运营Mu3e第一阶段实验。德国团队在实验准备过程中发挥了重要作用，并计划负责探测器的主要部件。其中包括由现代单片硅像素传感器构建的跟踪探测器，用于精确计时的闪烁计数器，以及包括基于GPU的处理器群的数据采集系统。

The project aims to set up a DFG-Research Unit for all German groups participating in the Mu3e experiment (Heidelberg, Karlsruhe and Mainz).With the Mu3e experiment we aim to search for the rare decay μ → eee with an ultimate sensitivity of less than B(μ → eee) <1E-16. This decay is allowed in the extended Standard Model (SM) of particle physics (with massive neutrinos), albeitan extremely small decay rate of << 1E-56 is predicted, which is why this decay is within the SM virtually unobservable . The discovery of this lepton flavor violating (LFV) decay would therefore manifest the existence of new physics beyond the SM.LFV processes are predicted by a variety of models beyond the SM. These include supersymmetry, Little Higgs models, models with extra (compactified) space dimensions, or grand unification theories. It is therefore not surprising that several groups around the world are preparing different experiments to search for LFV processes.The current experimental exclusion limit for the decay μ → eee comes from the SINDRUM experiment, which was performed more than 30 years ago, and is B(μ → eee) <1E-12 (90% confidence level). The Mu3e experiment thus ultimately seeks to improve the sensitivity by four orders of magnitude.In a first phase (Phase I), the Mu3e experiment will be performed at the PiE5 beamline at the Paul-Scherrer Institute (PSI, Switzerland), which provides a pure high-intensity muon beam. For phase I, a sensitivity of B(μ → eee)<5E-15 is expected after about 3 years of running time. Phase II will require a new, even more intense beamline, which is currently in the planning stage.Within the proposed Research Unit the German Mu3e groups plan to setup, commission and operate the Mu3e Phase I experiment. The German groups have been instrumental in the preparation of the experiment and plan to take responsibility for major components of the detector. These include the tracking detector build from modern monolithic silicon pixel sensors, the scintillation counters for precise timing, and the data acquisition system including a GPU-based processor farm.