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Mulan: a part-per-million measurement of the muon lifetime and determination of the Fermi constant

by R. Carey, T. Gorringe, D.W. Hertzog

Submission summary

As Contributors: Tim Gorringe
Preprint link: scipost_202102_00014v2
Date accepted: 2021-07-01
Date submitted: 2021-06-17 18:56
Submitted by: Gorringe, Tim
Submitted to: SciPost Physics Proceedings
Proceedings issue: RADCOR 2021 (15th International Symposium on Radiative Corrections: Applications of Quantum Field Theory to Phenomenology)
Academic field: Physics
  • Nuclear Physics - Experiment
Approach: Experimental


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-4π, 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 acquired a dataset of 1.6e12 positive muon decays and obtained a muon lifetime τ_µ = 2 196 980.3(2.2) ps (1.0 ppm) and Fermi constant G_F = 1.166 378 7(6) × 10−5 GeV^−2 (0.5 ppm). The thirty fold improvement in τ_µ has proven valuable for precision measurements in nuclear muon capture and the commensurate improvement in G_F has proven valuable for precision tests of the standard model.

Published as SciPost Phys. Proc. 5, 016 (2021)

List of changes

MSPS -> MSPS (mega samples per second)

added url for Balandin et al reference

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