The part-per-million measurement of the positive muon lifetime and determination of the Fermi constant by the MuLan experiment at the Paul Scherrer Institute is reviewed. The experiment used an innovative, time-structured, surface muon beam and a near-4pi, finely-segmented, plastic scintillator positron detector. Two in-vacuum muon stopping targets were used: a ferromagnetic foil with a large internal magnetic field, and a quartz crystal in a moderate external magnetic field. The experiment obtained a muon lifetime 2 196 980.3(2.2) ps (1.0 ppm) and a Fermi constant 1.166 378 7(6) 10^-5 GeV^-2 (0.5 ppm). The thirty-fold improvement in the muon lifetime has proven valuable for precision measurements in nuclear muon capture and the commensurate improvement in the Fermi constant has proven valuable for precision tests of the standard model.
Determination of the Muon Lifetime in $^{76}$Se with the MONUMENT experiment
University of Zurich（苏黎世大学）；University of Alabama（阿拉巴马大学）；Joint Institute for Nuclear Research（俄罗斯联合核子研究所）；IRFU, CEA, Université Paris-Saclay（法国原子能和替代能源署法国研究和技术中心萨克雷大学 IRFU）；Technical University of Munich（慕尼黑工业大学）；KU Leuven, Institute for Nuclear and Radiation Physics（荷语鲁汶大学核与辐射物理研究所）；Research Center on Nuclear Physics, Osaka University（大阪大学核物理研究中心）；Universiti Teknologi Malaysia（马来西亚理工大学）；Paul Scherrer Institut（保罗谢尔研究所）；Max-Planck-Institut für Kernphysik（马克斯·普朗克核物理研究所）
The cosmic rays data collected using a large area plastic scintillator array ISMRAN (Indian Scintillator Matrix for Reactor AntiNeutrino) are presented. The data collected serve as a useful benchmark of cosmogenic background in a non-reactor environment for the future measurements of electron-antineutrinos to be performed using the ISMRAN setup. The zenith angle distribution of the atmospheric muons has been measured and compared with Monte Carlo expectations. The detector setup was further used to measure the lifetime distribution of stopped muons and extract their rates inside the detector m…
Absolute intensity measurement of pulsed muon beams using in-beam activation
CMMS, TRIUMF（TRIUMF）；Department of Physics, Graduate School of Science, The University of Tokyo（东京大学理学研究科物理学系）；Nishina Center, RIKEN（理化学研究所仁科加速器科学研究中心）；ISIS Neutron and Muon Facility, STFC Rutherford Appleton Laboratory（STFC卢瑟福阿普尔顿实验室ISIS中子与μ子设施）；High Energy Accelerator Research Organization (KEK)（高能加速器研究机构(KEK)）；Department of Advanced Energy Science and Engineering, Kyushu University（九州大学先进能源工学部）；Research Center for Nuclear Physics, The University of Osaka（大阪大学核物理研究中心）
A high-pressure hydrogen time projection chamber for the MuCap experiment
Paul Scherrer研究所的MuCap实验对质子捕获核μ子的基本电弱过程的速率进行了高精度测量，$μ^- + p \rightarrow n + ν_μ$。实验方法基于使用时间投影室（TPC），该时间投射室在10巴的压力下在纯氢气中操作，并用作主动μ子停止靶。TPC在三维空间中探测单个μ子到达的轨迹，而传出衰变（Michel）电子的轨迹则由两个周围的线室和塑料闪烁描迹器测量。μ子和电子探测器一起使得能够精确测量$μp$原子的寿命，由此推导出核μ子捕获率。TPC也被用来监测氢气的纯度，通过检测元素杂质捕获μ子后的核反冲。本文详细介绍了TPC的设计和性能。
The Fermi constant ($G_F$) is extremely well measured through the muon lifetime, defining one of the key fundamental parameters in the Standard Model (SM). Therefore, to search for physics beyond the SM (BSM) via $G_F$, the constraining power is determined by the precision of the second-best independent determination of $G_F$. The best alternative extractions of $G_F$ proceed either via the global electroweak (EW) fit or from superallowed $β$ decays in combination with the Cabibbo angle measured in kaon, $τ$, or $D$ decays. Both variants display some tension with $G_F$ from muon decay, albeit …
