Tuning neutrino interaction models to inclusive electron scattering data

As the new generation of neutrino experiments draws ever closer, it is becoming increasingly apparent that the current systematic uncertainties associated with the underlying neutrino-nucleus interactions are not low enough to allow precision measurements of the oscillation parameters. To mitigate this, neutrino experiments are turning toward the electron scattering community to tune interaction models and increase their accuracy. This thesis focuses on the reduction of these systematic uncertainties by tuning interaction models and the calibration of water Cherenkov detectors.
Charged-current quasi-elastic neutrino interactions are T2K’s main signal process. This interaction is simulated under the impulse approximation and is later reweighted for use in the oscillation analysis. This approximation does not match other, more sophisticated, models and is an unintuitive depiction of Nature. To move beyond this, a neutral current elastic scattering framework is used to generate electron predictions from the NEUT generator, and is compared to a wide variety of inclusive electron scattering data. A semi-empirical correction is derived to account for discrepancies in the elastic peak position and is applied to the nucleon removal energy in the spectral function ground state model; this correction matches more theoretically rigorous methods, such as relativistic mean field approaches and optical potentials. Its impact on the oscillation analysis and the T2K observables, muon momentum and angle, is also discussed.
The development of an automated monitoring system for the UK light injection system installed in the Super-Kamiokande detector is also described. This is a detailed report on its functioning, which is designed for real-time feedback on the detector’s water quality. Attenuation measurements using a diffuser installed in the top of the tank are also implemented, the first analysis completed from the UKLI system, and compared to current, independent methods. This measurement allows for sensitive monitoring of the attenuation length change within the water volume.