Measurement of the Positive Muon Lifetime and Determination of the Fermi Constant to Part-per-Million Precision

We report a measurement of the positive muon lifetime to a precision of 1.0 ppm; it is the most precise particle lifetime ever measured. The experiment used a time-structured, low-energy muon beam and a segmented plastic scintillator array to record more than 2 X 10(12) decays. Two different stopping target configurations were employed in independent data-taking periods. The combined results give tau(mu)+(MuLan) = 2 196 980.3(2.2) ps, more than 15 times as precise as any previous experiment. The muon lifetime gives the most precise value for the Fermi constant: G(F)(MuLan) = 1.166 378 8(7) X 10(-5) GeV(-2) (0.6 ppm). It is also used to extract the mu(-)p singlet capture rate, which determines the proton's weak induced pseudoscalar coupling g(P).