Searching for charged lepton flavour violation with the Mu3e experiment - Scintillating Tile Detector

Mu3e第一阶段实验的主要目标是寻找违反衰变γ -> e e e e的带电轻子风味，在90%置信水平（CL）下，灵敏度为BR(γ→e e e) < 5 × 10−15，与现有界相比，相应的提高了200倍。为了达到Mu3e第一阶段的灵敏度目标，必须在大约一年的数据采集时间内观察到每秒10^8次μ子衰减。这需要出色的背景抑制能力。为了有效区分由随机巧合和内部转换的辐射衰减引起的背景信号事件，采用了高分辨率跟踪和顶点化以及非常精确的定时。定时信息由Mu3e定时系统提供，该定时系统由位于实验中心目标区域周围的一个薄闪烁光纤探测器（FID）和放置在反射站内的两个闪烁瓷砖探测器（TID）组成；由海德堡HD-KIP开发的所谓MuTrig芯片的硅光电倍增管（SiPMs）读出器检测两者的闪烁光。该项目涉及TID的生产、调试、维护和操作，以及用于TID和FID前端读出的MuTrig芯片的制造和验证。

The main goal of the Mu3e Phase I experiment is the search for the charged lepton flavour violating decay gamma -> e e e with a sensitivity of BR(gamma → e e e) < 5 × 10−15 at 90% confidence level (CL), corresponding to a factor 200 improvement compared to the existing bound. In order to reach the Mu3e Phase I sensitivity goal, of order 10^8 muon decays per second have to be observed for about one year of data taking time. This requires an excellent background rejection capability. To effectively distinguish signal events from background arising from random coincidences and radiative decays with internal conversion, high-resolution tracking and vertexing as well as very precise timing are used. The timing information is provided by the Mu3e timing system, consisting of a thin scintillating fiber detector (FID) located around the target region in the central part of the experiment, and two scintillating tile detectors (TID) placed inside the recurl stations; the scintillation light of both is detected by Silicon-Photomultipliers (SiPMs) readout with the so-called MuTrig chip developed at HD-KIP in Heidelberg. This project concerns the production, commissioning, maintenance and operation of the TID as well as the fabrication and validation of the MuTrig chip for the front-end readout of both TID and FID.