Improved Measurement of the Positive Muon Lifetime and Determination of the Fermi Constant

MuLan Collaboration; Chitwood, D. B.; Banks, T. I.; Barnes, M. J.; Battu, S.; Carey, R. M.; Cheekatmalla, S.; Clayton, S. M.; Crnkovic, J.; Crowe, K. M.; Debevec, P. T.; Dhamija, S.; Earle, W.; Gafarov, A.; Giovanetti, K.; Gorringe, T. P.; Gray, F. E.; Hance, M.; Hertzog, D. W.; Hare, M. F.; Kammel, P.; Kiburg, B.; Kunkle, J.; Lauss, B.; Logashenko, I.; Lynch, K. R.; McNabb, R.; Miller, J. P.; Mulhauser, F.; Onderwater, C. J. G.; Ozben, C. S.; Peng, Q.; Polly, C. C.; Rath, S.; Roberts, B. L.; Tishchenko, V.; Wait, G. D.; Wasserman, J.; Webber, D. M.; Winter, P.; Zolnierczuk, P. A.

Improved Measurement of the Positive Muon Lifetime and Determination of the Fermi Constant

Authors

Description

The mean life of the positive muon has been measured to a precision of 11 ppm using a low-energy, pulsed muon beam stopped in a ferromagnetic target, which was surrounded by a scintillator detector array. The result, tau_mu = 2.197013(24) us, is in excellent agreement with the previous world average. The new world average tau_mu = 2.197019(21) us determines the Fermi constant G_F = 1.166371(6) x 10^-5 GeV^-2 (5 ppm). Additionally, the precision measurement of the positive muon lifetime is needed to determine the nucleon pseudoscalar coupling g_P.
As published version (PRL, July 2007)