Speaker
Description
At Belle II, large and clean samples of $\tau$ leptons are produced and may decay to sterile neutrinos. For the relevant mass range, such sterile neutrinos are typically long-lived, leading to displaced-vertex (DV) signatures at colliders. Here, we study a DV search of sterile neutrinos at Belle II in the framework of the sterile-neutrino-extended Standard Model Effective Field Theory ($\nu$SMEFT). The production and decay of the sterile neutrinos can be realized via either the standard active-sterile neutrino mixing or higher-dimensional operators in $\nu$SMEFT. We perform Monte-Carlo simulations to estimate the Belle II sensitivities to such sterile neutrinos, and find that Belle II can probe non-renormalizable dimension-six operators involving one sterile neutrino up to 3 TeV in the new-physics scale.
