Degree
Doctor of Philosophy (PhD)
Department
Physics & Astronomy
Document Type
Dissertation
Abstract
Long-baseline neutrino oscillation experiments provide our best insight into the CP violation in the lepton sector. The T2K experiment has recently updated their measurement to address indications of over-constraints in our model which stemmed from a lack of freedom in the low-energy modeling of the nuclear response. The neutrino interaction model is updated with new model parameters to better describe the < 600 MeV region of observed neutrino interactions. The near detector constraint is also updated to include new high-angle and backward scattered events, increasing statistics by 13\%.
In this thesis, I highlight my contributions to this result from T2K. These studies test the performance of our neutrino interaction model to alternatively plausible interaction choices motivated by theory and other experiments. I also perform the Hybrid-Frequentist analysis to T2K data to determine the strength of CP-violation in neutrinos. We find that $\delta_{CP}=-2.04^{+1.06}_{-0.63}$ which excludes CP-conserving values at $2\sigma$ and is consistent with our previous result. I perform studies that aim at elucidating key improvements to the analysis and re-perform a series of robustness studies to assess the biases incurred by the new interaction model. Although the bias from alternative nuclear response models improves, an additional smearing of $1.9\times10^{-5}$ $\text{eV}^2$ is recommended for $\Delta m^2_{32}$ results. In addition to the oscillation analysis results, I discuss my contributions made to the construction and operation of a novel fully active 3D scintillator detector called SuperFGD. Given it's precise time resolution, SuperFGD facilitates the reconstruction of neutrons associated with neutrino interactions opening the opportunity for improved neutrino energy reconstruction. While still incorporating this new data into the oscillation analysis, SuperFGD will provide a more complementary constraint on neutrino interactions at HyperKamiokande and facilitate closer study of nuclear effects in neutrino measurements.
Date
5-12-2026
Recommended Citation
Schefke, Tristan, "New Constraints on the CP-violating phase with the T2K Experiment" (2026). LSU Doctoral Dissertations. 7089.
https://repository.lsu.edu/gradschool_dissertations/7089
Committee Chair
Kutter, Thomas
LSU Acknowledgement
1
LSU Accessibility Acknowledgment
1