论文标题
MEG II实验状态和前景
MEG II experiment status and prospect
论文作者
论文摘要
瑞士Paul Scherrer Institute（PSI）的MEG II实验旨在在违反了违反的Lepton风味的$ 6 \ times10^{ - 14} $的敏感性违反损失$μ^+\ to e^+γ$上。该衰减的当前上限为$ 4.2 \ times10^{ - 13} $在90％置信度（CL），由MEG的第一阶段设置。使用PSI MUON光束以降低的强度为$ 3 \ times10^7〜μ^+/$ s来实现此结果，以使背景保持在可管理的水平。 MEG〜II中升级的检测器可以应对更高的强度，因此该实验预计将以$ 7 \ times10^7〜μ^+/$ s强度运行。新的低质量，单卷，高粒度跟踪器以及一个新的高度分割的时序计数器，确保了正电子检测更好的分辨率。此外，在液体Xenon光子检测器内部的内部面上替换旧的光电倍增管（PMTS）用多像素光子计数器（MPPC）改善其性能。将讨论升级的探测器及其目前状态的细节，以及去年预设计跑步的最新结果以及2021年运行的视角，第一个配备了所有探测器和电子设备。
The MEG II experiment at Paul Scherrer Institute (PSI) in Switzerland aims to achieve a sensitivity of $6\times10^{-14}$ on the charged lepton flavor violating decay $μ^+\to e^+γ$. The current upper limit on this decay is $4.2\times10^{-13}$ at 90% Confidence Level (CL), set by the first phase of MEG. This result was achieved using the PSI muon beam at a reduced intensity, $3\times10^7~μ^+/$s, to keep the background at a manageable level. The upgraded detectors in MEG~II can cope with a higher intensity, thus the experiment is expected to run at a $7\times10^7~μ^+/$s intensity. The new low mass, single volume, high granularity tracker, together with a new highly segmented timing counter, guarantees better resolutions for the positron detection. Moreover, the replacement of the old PhotoMultiplier Tubes (PMTs) with Multi-Pixel Photon Counters (MPPCs) in the inner face of the liquid xenon photon detector improved its performance. The details of the upgraded detectors and their present status will be discussed, together with the latest results from last year's pre-engineering run and the perspective for the 2021 run, the first with all the detectors and electronics installed.
