The Decay of Tau Leptons Produced in Neutrino-Nucleon Scatterings

Energy and angular distributions of the tau decay products in the CERN-to-Gran Sasso ${\nu }_{\tau }$ appearance experiments are studied for the decay modes $\tau \to \pi \nu$ and $\tau \to l\bar{\nu }\nu$ (l=e or mu). We find that the decay particle distributions in the laboratory frame are significantly affected by the tau polarization. Rather strong azimuthal asymmetry of $p{i}^{-}$ and $l^{-}$ about the tau momentum axis is predicted, which may have observable consequences even at small statistics experiments.