Improved Measurement of the Positive Muon Lifetime and Determination of the Fermi Constant
Abstract
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, taumu = 2.197013(24) us, is in excellent agreement with the previous world average. The new world average taumu = 2.197019(21) us determines the Fermi constant GF = 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 gP.
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