Development of a Tracking Detector for the Mu3e-Experiment based on novel thin High-Voltage Monolithic Active Pixel Sensors

基于薄高压单片有源像素传感器(HV-MAP)，目前正在研制一种用于Mu3e实验的全尺寸跟踪探测器。Paul-Scherrer研究所(PSI，瑞士)的Mu3e实验旨在寻找分支比灵敏度优于10^{-16}的轻子味违反衰变Muon-gt；eee。为了达到预定的灵敏度，需要一种低质量、高分辨率的像素探测器，该探测器具有能够在高粒子率下工作的薄像素层。为了满足这些要求，提出了一种新的探测器概念：厚度在50微米或更小的超薄HV-MAP传感器，基于聚酰亚胺薄膜的超轻支撑结构，以及使用氦气冷却探测器。与标准的硅像素探测器相比，上述每一种措施都可以显著减少多次库仑散射，并以每秒超过10亿个Muon衰变的非常高的速率测量高分辨率的低动量径迹。该项目的目标是基于新的HV-MAP技术建立一个小型像素探测器原型，并使其有资格为Mu3e实验进行批量生产。建议的跟踪探测器也可以用于其他在高粒子率下运行的低能量实验。

Based on thin High-Voltage Monolithic Active Pixel Sensors (HV-MAPS) a full scale tracking detector is currently developed for the Mu3e-experiment. The Mu3e-experiment at the Paul-Scherrer Institute (PSI, Switzerland) aims for a search of the lepton flavor violating decay muon -> eee with a branching ratio sensitivity of better than 10^{-16}. To achieve the aimed sensitivity a low mass high resolution pixel detector with thin pixel layers capable to operate at high particles rates is required. To fulfill these requirements a novel detector concept is proposed: ultra-thin HV-MAPS sensors with a thickness of 50 micrometer or less, an ultra-light support structure based on a polyimide foil and detector cooling by using helium gas. Each of the above measures allow to significantly reduce multiple Coulomb scattering compared to standard silicon pixel detectors and to measure low momentum tracks with high resolution at very high rates with more than 1 billion muon decays per second.The goal of the project is to build a small prototype pixel detector based on the new HV-MAPS technology and to qualify it for a series production fo the Mu3e experiment. The proposed tracking detector might also be used for other low energy experiments operating at high particle rates.