Measurement of the muon antineutrino charged current single charged pion production cross-section on water and hydrocarbon with ND280

Tokai to Kamioka (T2K) is a long-baseline neutrino oscillation experiment based in Japan, performing measurements of neutrino oscillations and neutrino-nucleus interactions.
Uncertainty in the modelling of neutrino-nucleus interactions on the order of GeV is a significant systematic uncertainty in T2K and other current oscillation experiments, and is set to become a limiting uncertainty in many measurements as new experiments are constructed.
These uncertainties result from the difficulty in modelling the effects of the nuclear medium on the underlying neutrino interaction, where the kinematics and spatial distribution of nucleons is well understood for only the lightest nuclei. As such, a much improved understanding of nuclear effects on neutrino interactions is essential for neutrino interaction experiments of the near future.
This thesis describes the first measurement of the muon anti-neutrino charged current single pion production cross-sections on water and hydrocarbon using the
passive water and active scintillator targets in the T2K ND280 near detector.
The cross-section is measured as a function of the outgoing pion kinematics, which depend heavily on both the underlying neutrino interaction models and nuclear state model,
and can be directly measured for each event by the detector, reducing dependence on the input simulation.
A novel method of collapsing a double differential cross-section measurement into two correlated single differential cross-section measurements is presented and validated for this analysis.
It is hoped that this measurement will provide additional constraints on neutrino-nucleus pion production models, enabling better understanding of the shortcomings in these models and where improvements are required.