Solar neutrinos at DUNE

The Deep Underground Neutrino Experiment, DUNE, is a future long-baseline neutrino experiment, starting from the Fermi National Accelerator Laboratory, FNAL, to the Sanford Underground Research Facility, SURF. The far detector complex at SURF will consist of four 17-ktonne liquid-argon time projection chambers, LArT- PCs. DUNE’s long-baseline physics program aims to evaluate neutrino oscillation parameters, the CP-violating phase, dCP , and determine the neutrino mass hierarchy. DUNE’s low-energy physics program aims to observe solar neutrinos and those em- anating from core-collapse supernovae. The low-energy program relies on carefully controlled systematic uncertainties and well-understood radiological backgrounds, pertinent at the O(1 - 100) MeV domain. This thesis presents two analyses. The first is a detailed examination of the radiolog- ical neutrons at DUNE. Neutron capture on argon can be confused with low-energy neutrino interactions. We know neutrons emanate from the cavern walls, aggre- gate construction materials and various types of steel, including those used within the DUNE cryostats. With improvements to the simulation geometry and energy spectra informed by elemental spectroscopy on material samples, the total neutron capture rate is estimated to be 3.05 ± 0.13 captures / 10 ktonne-second. Secondly, the improvements required of a far detector module to observe CNO neu- trinos are discussed. Inconsistencies in available solar neutrino data imply two pos- sible neutrino fluxes relating to higher and lower solar metallicity models. Under DUNE’s baseline configuration, CNO neutrino observation is unlikely. However, a low-background far detector module with improved systematic uncertainties would allow for an almost 5s measurement of CNO neutrinos under a high metallicity model. Additionally, DUNE could separate the high from low metallicity model at a > 3s confidence level. This measurement would resolve the solar metallicity discrepancy.