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RESEARCH PRODUCT

Updated Results from the $\nu_{\tau}$ Appearance Search in NOMAD

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description

Updated results from the appearance searches for $\numunutau$ and $\nuenutau$ oscillations in the full NOMAD data sample are reported. The increased data and the use of more refined kinematic schemes for the $\nutau$ CC selection allow a significant improvement of the overall sensitivity. The ``blind analysis" of both the deep-inelastic and the low multiplicity samples yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90\% C.L. region in the $\sin^22\theta_{\mu\tau} - \Delta m^2$ plane which includes $\sin^22\theta_{\mu\tau}\ <\ 4.4\times10^{-4}$ at large $\Delta m^2$ and $\Delta m^2 < 0.8$ eV$^2$/$c^4$ at $\sin^22\theta_{\mu \tau}=1$. The corresponding contour in the $\nuenutau$ oscillation hypothesis results in $\sin^22\theta_{e\tau}\ <\ 2.2\times10^{-2}$ at large $\Delta m^2$ and $\Delta m^2 < 6.5$ eV$^2$/$c^4$ at $\sin^22\theta_{e \tau}=1$.