Colin Anderson
Elucidating the nature of neutrino oscillation continues to be a goal in the vanguard of the efforts of physics experiment. As neutrino oscillation searches seek an increasingly elusive signal, a thorough understanding of the possible backgrounds becomes ever more important. Measurements of neutrino-nucleus interaction cross sections are key to this understanding. Searches for vμ → ve oscillation – a channel that may yield insight into the vanishingly small mixing parameter &thetas; 13, CP violation, and the neutrino mass hierarchy— are particularly susceptible to contamination from neutral current single π° (NC 1π°) production. Unfortunately, the available data concerning NC 1π° production are limited in scope and statistics. Without satisfactory constraints, theoretical models of NC 1π° production yield substantially differing predictions in the critical Ev ∼ 1 GeV regime. Additional investigation of this interaction can ameliorate the current deficiencies.
The Mini Booster Neutrino Experiment (MiniBooNE) is a short-baseline neutrino oscillation search operating at the Fermi National Accelerator Laboratory (Fermilab). While the oscillation search is the principal charge of the MiniBooNE collaboration, the extensive data (∼106 neutrino events) offer a rich resource with which to conduct neutrino cross section measurements. This work concerns the measurement of both neutrino and antineutrino NC π° production cross sections at MiniBooNE. The size of the event samples used in the analysis exceeds that of all other similar experiments combined by an order of magnitude. We present the first measurements of the absolute NC 1π° cross section as well as the first differential cross sections in both neutrino and antineutrino mode. Specifically, we measure single differential cross sections with respect to pion momentum and pion angle. We find the flux-averaged, total cross sections for NC 1π° production on CH2 to be (4.76 ± 0.05stat ± 0.76sys) × 10 -40 cm2/nucleon at 〈Ev〉 = 808 MeV for neutrino induced production and (1.48 ± 0.05stat ± 0.23sys) × 10-40 cm 2/nucleon at 〈Ev〉 = 664 MeV for antineutrino induced production.