Measurement of a neutral current PI0 cross section in the NOvA near detector

Abstract

The NOvA long-baseline neutrino experiment is attempting to measure properties of subatomic particles called neutrinos in order to discover information about the universe. NOvA is a project based out of Fermi National Accelerator Laboratory and funded by the U.S. Department of Energy. The experiment works by firing an extremely high energy beam of neutrinos through the earth at a 14 kiloton detector located hundreds of miles away. This research focused on studying one specific background to the NOvA measurement called neutral current pion production. The goal of the study is to understand how to identify this type of background and consider it when performing measurements for NOvA. Additionally, a cross-section can be calculated to determine the probability of this type of interaction occurring in the detector. To understand neutral current pion productions, a preliminary cuts-based analysis was performed by hand to separate them from other interactions in the detector. Next, simulated data was fed into a boosted decision tree algorithm, a very powerful tool for separating neutral current pion production interactions from other interactions. After the initial separation, a sideband study was performed to minimize systematic errors. To determine the cross-section, the efficiency and purity of event selection was estimated, and the sideband study was utilized to calculate the cross-section uncertainty. After calculating a single cross-section, a resolution study will be performed to determine if a differential cross-section can be measured. Using this study, NOvA will be able to consider neutral current pion interactions in its final results.