On the Role of the $\nu_\tau$ Appearance in DUNE in Constraining Standard Neutrino Physics and Beyond

We consider the $\nu_\mu \to \nu_{\tau}$ appearance channel in the future Deep Underground Neutrino Experiment (DUNE) which offers a good statistics of the $\nu_{\tau}$ sample. In order to measure its impact on constraining the oscillation parameters, we consider several assumptions on the efficiency for $\nu_\tau$ charged-current signal events (with subsequent $\tau \to e$ decay) and the related backgrounds and study the effects of various systematic uncertainties. Two different neutrino fluxes have been considered, namely a CP-violation optimized flux and a $\nu_\tau$ optimized flux. Our results show that the addition of the $\nu_\mu \to \nu_{\tau}$ appearance channel does not reduce the current uncertainties on the standard 3-$\nu$ oscillation parameters while it can improve in a significant way the sensitivity to the Non-Standard Interaction parameter $|\epsilon_{\mu\tau}|$ and to the new mixing angle $\theta_{34}$ of a sterile neutrino model of the $3+1$ type.