Background Reduction in Neutrino Oscillation Analyzes for a Liquid Argon-based Long-Baseline Neutrino Experiment

The Long-Baseline Neutrino Experiment collaboration has developed a design for a next generation U.S. long-baseline neutrino experiment consisting of a large liquid argon neutrino detector 1300 km downstream of a wide-band neutrino beam. The goal of the experiment is to measure neutrino flavor oscillations, and to look for charge-parity symmetry violation (CPV) in the lepton sector. Simulations using a parametrized detector response are analyzed to determine the experimental sensitivity of the proposed design to CPV. Event selection algorithms, based on the identification of final-state lepton candidates, have a significant background acceptance from neutral-current (NC) interactions and charge-current (CC) $\nu_\tau$ interactions producing $\tau$ leptons which decay leptonically. In this work an improvement in the rejection of CC$\nu_\tau$ and NC backgrounds is explored for $\nu_e$-~appearance and $\nu_\mu$-~disappearance analysis samples. A multivariate analysis discriminator built from reconstructed kinematic variables, especially transverse momentum, has been shown to significantly improve background rejection with little loss in signal efficiency. Estimates for the improvements in background rejection and the changes in sensitivity for CPV determination will be presented.