Search for the rare decay mü ---> eee with a high rate experiment based on thin Monolithic Active Pixel Sensors

基本粒子物理学的标准模型包括三个类电子粒子（电子、μ子和τ子）和三个中微子，统称为轻子。长期以来，人们认为每种轻子（味轻子）的数量是守恒的。自从中微子振荡被发现后，人们就知道事实并非如此;然而，到目前为止，违反带电轻子味的跃迁还没有被探测到。轻子味破坏相互作用的机制和大小是非常有趣的，因为它们与中微子质量的产生，CP破坏和超越标准模型的新物理学有关。这个项目是为了寻找灵敏度为1/1016 μ衰变的轻子味破坏跃迁μ+ → e+e−e+的实验。为了达到这种灵敏度，必须通过由薄硅高压单片有源像素传感器（HV-MAPS）构建的检测器精确重建高达每秒十亿μ衰变的衰变电子的动量。该项目包括此类探测器（同类产品中的第一个）的设计，建造和操作，重点是在强大的电子组件（如现场可编程门阵列（FPGA）和图形处理单元（GPU））上实现的相关电子和在线轨道重建方法。

The standard model of elementary particle physics encompasses three electron-like particles (the electron, the muon and the tau) and three neutrinos, together known as leptons. It was long believed that the number of leptons of each kind (flavour ) is conserved. Since the discovery of neutrino oscillations it is known that this is not the case; transitions violating charged lepton flavour have however so far eluded detection. The mechanism for and size of lepton flavour violating interactions are of great interest, as they are linked to the generation of neutrino masses, CP violation and new physics beyond the standard model. This project is for an experiment searching for the lepton flavour violating transition μ+ → e+e−e+ with a sensitivity of one in 1016 μ decays. In order to reach that sensitivity, the momenta of the decay electrons from up to a billion μ decays per second have to be precisely reconstructed by a detector built from thin silicon high-voltage monolithic active pixel sensors (HV-MAPS). This project encompasses the design, construction and operation of such a detector (the first of its kind), with a focus on the associated electronics and on-line track reconstruction methods implemented on powerful electronics components such as Field Programmable Gate Arrays (FPGAs) and Graphics Processing Units (GPUs).