HEE Seminar: "Heavy Neutrinos in Ice, Water, Dirt, and Plastic" (N. Kamp, Harvard)

From the continuous energy spectrum of beta decay electrons to the disappearance of neutrinos from the Sun and the atmosphere, experimental anomalies have catalyzed progress in neutrino physics since the 1930s. One of the longest-standing anomalies in the neutrino sector is the 4.8 sigma excess of electron-like events observed by the MiniBooNE experiment at Fermilab. This talk covers an array of investigations into the nature of the excess. We begin with the follow-up MicroBooNE experiment, which searched for electron neutrino and delta radiative decay interpretations of the anomaly. The outcome of these searches motivates an alternative solution for the excess: heavy neutral leptons (HNLs) with a transition magnetic moment coupling to Standard Model neutrinos. We derive phenomenological constraints on these dipole-portal HNLs using data from the plastic scintillator tracking detector of MINERvA and the gaseous argon time projection chambers of ND280. Next, we discuss a novel search for "double cascades" from dipole-portal HNLs at the South-Pole-based IceCube and Mediterranean-Ocean-based KM3NeT observatories. We further examine the sensitivity of these neutrino telescopes to the minimal heavy neutral leptons that appear in Type I Seesaw models of neutrino mass. Finally, we introduce two new concepts for experimental that take advantage of natural environment surrounding the LHC 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 LHC-generated neutrinos, these experiments can perform novel searches for minimal 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.