Majorana neutrinos and low-energy tests of electroweak models

Tests based on neutrinoless double-$\beta$ decay and rare muon processes are proposed for the detection of a heavy Majorana neutrino with a mass of ∼100 GeV. Existence of such a neutrino would distinguish between the standard and left-right-symmetric electroweak gauge models with U(1) in the latter identified with ($B-L$). The sensitivity of these processes to the mass of the heavy Majorana neutrino is discussed.