Abstrakt
We report on a search for a heavy Majorana neutrino in the decays τ- RIGHTWARDS ARROW π-νh, νh RIGHTWARDS ARROW πlMINUS-OR-PLUS SIGN, l 1/4 e, μ.
The results are obtained using the full data sample of 988 fb-1 collected with the Belle detector at the
KEKB asymmetric energy eþe- collider, which contains 912 x 106 ττ pairs. We observe no significant signal and set 95% CL upper limits on the couplings of the heavy right-handed neutrinos to the conventional standard model left-handed neutrinos in the mass range 0.2-1.6 GeV=c2. This is the first study of a mixed couplings of heavy neutrinos to τ leptons and light-flavor leptons.