Indirect methods for determining heavy-neutrino masses

Within the two-flavor approximation, equations that relate the oscillation parameters for both light and heavy neutrinos to the Yukawa coupling constants and the vacuum expectation values of the Higgs fields are derived within the left-right model. The contributions from Higgs bosons to the muon anomalous magnetic moment, to the cross sections for lepton-flavor-violating processes, and to the cross sections for low-energy light-neutrino scattering are studied in order to determine the Yukawa coupling constants. It is shown that the heavy-neutrino masses m{sub N12} can be expressed in terms of only the triplet Yukawa coupling constants and the mass of the gauge boson W{sub 2}. Data on direct and inverse muon decay and constraints on the masses of the {delta}-tilde{sup (-)}, {delta}{sup (--)}{sub 1,2}, and W{sub 2} bosons are used to obtain bounds on m{sub N1,2} both in the absence of degeneracy and in the presence of mass degeneracy in the sector of heavy neutrinos. Only in the case of degeneracy are data concerning the explanation of the (g-2){sub {mu}} anomaly used to determine bounds on m{sub N1,2}.