Search for a heavy neutrino state in the decay pi(+)->mu(+)+nu(mu)

摘要

We have searched for an admixture of a heavy neutrino state nu(3) in the decay pi(+) --> mu(+)+ nu(mu) by analyzing the momentum spectrum of a surface muon beam in a magnetic spectrometer. No indications for such a neutrino state were found. In the mass range 0.53 MeV less than or equal to m(nu x) less than or equal to 1.0 MeV, not covered by previous experiments, we obtain upper limits of the branching fraction Gamma(pi(+) --> mu(+) nu(x))/[ Gamma(pi(+) --> mu(+) nu(2)) + Gamma(pi(+) --> mu(+) nu(x))] between 22 % and 1.6 % (c.l. = 0.9). (C) 1998 Elsevier Science B.V. All rights reserved. [References: 8]