Improved measurement of the positive-muon lifetime and determination of the fermi constant

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) mu s, is in excellent agreement with the previous world average. The new world average tau(mu)=2.197019(21) mu s determines the Fermi constant G(F)=1.166371(6)x10(-5) GeV-2 (5 ppm). Additionally, the precision measurement of the positive-muon lifetime is needed to determine the nucleon pseudoscalar coupling g(P).