Measurement of the muon-neutrino charged-current single charged-pion cross-section on argon with the MicroBooNE detector

Abstract

Several important questions remain open in the field of neutrino oscillation physics, including the possibility of CP-violation in the lepton sector, the ordering of the neutrino mass states and the possible existence of sterile neutrinos. At present, the ability to answer these questions is limited by uncertainties on neutrino-nucleus interaction cross-section models. Consequently, it is key that these uncertainties are constrained by precise cross-section measurements made using experimental data. The MicroBooNE experiment utilises a 90-tonne active mass Liquid Argon Time Projection Chamber to image neutrino interactions at the millimetre scale and is ideally suited to measure complex neutrino-argon interactions.

This thesis presents a measurement of the muon-neutrino charged-current single charged pion (CC1π± ) cross-section on argon using data from MicroBooNE in the Fermilab Booster Neutrino Beam. The total flux-integrated forward-folded cross-section is found to be [22.4 ± 0.9 (stat.) ± 5.2 (syst.)] × 10 −41 cm 2, with an efficiency of [18.8 ± 1.3]% and is consistent with the prediction of the GENIE generator. Additionally, the world’s first measurement of the proton-exclusive CC1π ± cross-section is performed with a 300 MeV c−1 proton momentum threshold. Finally, the differential cross-section is extracted with respect to the muon and pion momenta and directions. The pion momentum measurement on argon is also the first to be made.

To facilitate these measurements, the Pandora pattern recognition software is employed to identify and reconstruct particle trajectories in MicroBooNE data. A key stage of this process is the identification and removal of cosmic-rays that form the main background to all analyses of neutrino interactions. The approach presented in this thesis is capable of removing 46% of such backgrounds at the cost of only 1.7% of neutrino-induced activity.