Measurement of the Fermi Constant by FAST
hep-ex
/ Authors
A. Barczyk, J. Kirkby, L. Malgeri, J. Berdugo, J. Casaus, C. Mana, J. Marin, G. Martinez, E. Sanchez, C. Willmott
and 5 more authors
/ Abstract
An initial measurement of the lifetime of the positive muon to a precision of 16 parts per million (ppm) has been performed with the FAST detector at the Paul Scherrer Institute. The result is tau_mu = 2.197083 (32) (15) microsec, where the first error is statistical and the second is systematic. The muon lifetime determines the Fermi constant, G_F = 1.166353 (9) x 10^-5 GeV^-2 (8 ppm).