Constraining systematic uncertainties in the T2K neutrino oscillation analysis using samples from the off-axis near detector

带电电流 (CC) 中微子相互作用对于 T2K 实验及其振荡分析特别重要。在没有振荡的情况下，远检测器处的​​ CC 相互作用的预期数量可以使用来自近检测器的信息来预测。 T2K 离轴近探测器 (ND280) 上的带电电流样本根据最终状态下存在的带电π介子数量分为三类。这三个类别是 CC0pi、CC1pi 和 CCother，分别指带 0、1 和 >1 个带电π介子的事件。 “CCother”样本包含最终状态为 pi0 的所有 CC 样本。因此，CCother 样本的子集将包含主要来自 pi0 衰变的光子。本论文将开发一个新的选择，将CCother选择分为“带光子的CCother”和“不带光子的CCother”。选择的结果将被纳入 T2K 振荡分析框架中，从而用于改善与此类事件相关的系统不确定性。了解 CC 与最终状态下的伽玛相互作用对于将在本论文的时间范围内开始的联合 NoVA-T2K 分析尤其重要。因此，该项目将使用来自近探测器的数据开发一组新样本，并将其纳入实验的振荡分析中。

Charged-current (CC) neutrino interactions are of particular importance to the T2K experiment and its oscillation analyses. The expected number of CC interactions at the far detector in the case of no oscillations can be predicted using information frm the near detectors. Charged-current samples at the T2K off-axis near detector (ND280) are split into three categories depending on how many charged pions are present in the final state. The three categories are CC0pi, CC1pi and CCother which refer to events with 0, 1 and >1 charged pions respectively. The "CCother" sample contains all CC samples with a final-state pi0. Therefore, a subset of CCother sample will contain photons, primarily from pi0 decays. This thesis will develop a new selection to divide the CCother selection into "CCother with photon" and "CCother without photon". Results from the selection will be implemented into the T2K oscillation analysis framework and thus used to improve the systematic uncertainty associated with such events. Knowledge of CC interactions with a gamma in the final state is especially important for the joint NoVA-T2K analysis which will begin in the timeframe of this thesis. This project will therefore develop a new set of samples using data from the near detector and incorporate them into the oscillation analysis for the experiment.