Measurement of Neutron Production in Neutrino - Argon Interactions at MicroBooNE

Abstract

Neutrons produced in neutrino–argon interactions play an important role in shaping observable final states in liquid-argon time projection chambers, yet they are difficult to detect and remain a significant source of modeling uncertainty. This thesis presents a focused study of neutrino–argon interactions that produce neutrons in the final state using the MicroBooNE detector exposed to the Booster Neutrino Beam at Fermilab. A detailed investigation of neutron behavior in liquid argon is performed to characterize neutron transport, scattering, and detectability in MicroBooNE, informing the development of a neutron-tagged event selection that identifies neutron-induced secondary proton tracks and extends standard charged-current topologies to explicitly include neutron information. New kinematic imbalance observables are introduced to probe correlations between the outgoing muon, proton, and reconstructed neutron directions, complementing existing missing-momentum variables. A comprehensive uncertainty model is constructed, including contributions from neutrino flux, interaction modeling, detector response, hadron reinteractions, and finite sample statistics, with a dedicated treatment of neutron reinteraction uncertainties incorporated into the MicroBooNE analysis framework. Event-selection and reconstructed-distribution studies, as well as the extracted single-bin cross-section result, use the full Run 1–5 MicroBooNE data set. Together, these developments enable the first measurement of a neutrino-induced neutron production cross section in liquid argon, establishing a benchmark for neutron modeling in neutrino–argon interactions and providing a foundation for future measurements in liquid-argon detectors.