Final NOMAD results on νμ → ντ and νe → ντ oscillations including a new search for ντ appearance using hadronic τ decays

Results from the v, appearance search in a neutrino beam using the full NOMAD data sample are reported. A new analysis unifies all the hadronic tau decays, significantly improving the overall sensitivity of the experiment to oscillations. The blind analysis of all topologies yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90% CL allowed region in the sin(2)2 theta (mu tau)-Deltam(2) plane which includes sin(2)2 theta (mu tau) < 3.3 x 10(-4) at large Deltam(2) and Deltam(2) < 0.7 eV(2)/c(4) at sin(2) 2 theta (mu tau) = 1. The corresponding contour in the nu (e) --> nu (tau) oscillation hypothesis results in sin(2) 2 theta (l tau) < 1.5 x 10(-2) at large Deltam(2) and Deltam(2) < 5.9 eV(2)/c(4) at sin(2) 2 theta (l tau) = 1. We also derive limits on effective couplings of the tau lepton to nu (mu) or nu (l). (C) 2001 Elsevier Science B.V. All rights reserved.