First results from the MuLan and MuCap experiments

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

MuLan and MuCap are ongoing experiments at the Paul Scherrer Institut, Switzerland, that use the muon lifetime to determine fundamental weak interaction parameters. The goal of MuLan is a 1 ppm measurement of the positive muon lifetime τμ+ to determine the Fermi constant G F to 0.5 ppm. The goal of MuCap is to make a 1% determination of the rate ΛS of the process of nuclear muon capture by the proton, μp→nν, by measuring the μ- disappearance rate in hydrogen gas to 10 ppm and subtracting the world average for the μ+ decay rate. A 1% determination of the capture rate ΛS is of interest because it would enable a 7% determination of gP, the induced pseudoscalar coupling of the nucleon. In 2007, both experiments published first results based upon data collected by each in 2004. MuLan reported an 11 ppm μ+ lifetime measurement, τμ+=2.197013(24)μs, resulting in a new, 9.6 ppm world average, τμ+=2.197019(21)μs, which determines the Fermi constant, GF=1.166371(6)×10-5GeV-2, to 5 ppm. MuCap reported a 3% measurement of the muon capture rate from the hyperfine singlet ground state of the μp atom, ΛS=725.0±17. 4s-1, from which a 15% value for the pseudoscalar coupling, g P(q2=-0.88mμ2)=7.3±1.1, was extracted.

Original languageEnglish (US)
Title of host publicationNeutrino Factories, Superbeams and Betabeams - 9th International Workshop on Neutrino Factories, Superbeams, and Betabeams, NuFact 07
Pages372-374
Number of pages3
DOIs
StatePublished - Mar 17 2008
Event9th International Workshop on Neutrino Factories, Superbeams, and Betabeams, NuFact 2007 - Okayama, Japan
Duration: Aug 6 2007Aug 11 2007

Publication series

NameAIP Conference Proceedings
Volume981
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Conference

Conference9th International Workshop on Neutrino Factories, Superbeams, and Betabeams, NuFact 2007
CountryJapan
CityOkayama
Period8/6/078/11/07

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Keywords

  • Fermi constant
  • Muon capture
  • Muon lifetime
  • Pseudoscalar form factor

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Banks, T. I. (2008). First results from the MuLan and MuCap experiments. In Neutrino Factories, Superbeams and Betabeams - 9th International Workshop on Neutrino Factories, Superbeams, and Betabeams, NuFact 07 (pp. 372-374). (AIP Conference Proceedings; Vol. 981). https://doi.org/10.1063/1.2898992