Speaker
Description
Long-lived particles (LLPs) could serve as portal to hidden sectors addressing different open problems of the Standard Model (SM). Among these, the evidence for neutrino masses and mixings—observed in neutrino oscillation experiments—stands out as particularly promising. A simple extension to the SM involves the inclusion of heavy right-handed neutrinos, commonly known as heavy neutral leptons (HNLs). In minimal models, the HNL production and decay are governed by weak interactions, suppressed by their mixing with active neutrino. This suppression leads to relatively long HNL lifetimes when their masses lie within the MeV–GeV range. The near detector complexes of current and upcoming neutrino oscillation experiments provide an optimal environment for searching visible HNL decays, given the high intensity of the beams, and the volume of the detectors involved. This talk will use two experiments as benchmarks to discuss sensitivity projections for the coming years. The first is ICARUS, the far detector of the Short Baseline Neutrino (SBN) program, exposed to the 120 GeV proton NuMI beam. The second is the gaseous argon TPC of the Deep Underground Neutrino Experiment (DUNE), planned for the Phase II of the experiment. Our analysis indicates that, thanks to the high-energy, high-intensity proton beam, and advanced detector capabilities of these experiments, the projected constraints on the HNL mixing as a function of its mass will be highly competitive with existing experimental limits. To wrap up, the DUNE expected sensitivity to additional beyond-the-SM extensions, including scalar, axion, and vector portals will be reviewed.