2021/08/20 by Robert Carey, Rebecca Carey, Robert M. Carey +7 · 1 citation
Engineering · Physics and Astronomy · #Condensed matter physics #Constant (computer programming) #Dark Matter and Cosmic Phenomena #Detector #Fermi Gamma-ray Space Telescope #Magnetic field #Muon #Muon and positron interactions and applications #Nuclear physics #Optics #Particle physics theoretical and experimental studies #Physics #Scintillator #hep-ex #nucl-ex #physics.ins-det
paper · pdf · doi:10.21468/scipostphysproc.5.016
7 pages, 2 figures
arxiv created 2021/08/20 · arxiv updated 2021/08/23 · openalex publication_date 2021/09/06 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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.