Description:

Heavy neutral leptons (HNLs) are among the most promising candidates for physics beyond the Standard Model. These right-handed gauge singlets can couple to left-handed neutrinos through different portals, including mass mixing and transition magnetic moments. Both of these portals can be investigated across a variety of neutrino experiments. We first discuss HNLs with a transition magnetic moment—also known as dipole-portal HNLs—within the context of the longstanding excess of electromagnetic events observed in the MiniBooNE detector. We derive new constraints on these dipole-portal HNLs using accelerator neutrino data from the MINERvA and ND280 detectors. Next, we turn to neutrino telescopes, including the South-Pole-based IceCube observatory and Mediterranean-Ocean-based KM3NeT observatory. In these detectors, both mass-mixed and dipole-portal HNLs can leave a unique "double cascade" signature in the detector. We discuss the current status of searches for such double cascades and the prospects for improved searches in the future. Finally, we introduce two new experimental concepts that take advantage of the natural environment surrounding the Large Hadron Collider to collect large samples of collider-generated neutrinos: SINE, which observes neutrino interactions in bedrock, and UNDINE, which observes neutrino interactions in Lake Geneva. Due to the high energy scale of these neutrinos, SINE and UNDINE can perform novel searches for mass-mixed HNLs and constrain the forward production of charmed hadrons in proton-proton collisions. The latter of these has important implications for investigations into the origin of cosmic neutrinos at IceCube, KM3NeT, and beyond.

Nicholas Kamp, Postdoctoral Fellow, Harvard University

Host: Adrian Thompson