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

荷电中微子相互作用对T2K实验及其振荡分析具有特别重要的意义。在没有振荡的情况下，可以使用来自近探测器的信息来预测在远探测器处的CC相互作用的预期数目。在T2K离轴近探测器(ND280)处的带电电流样本被分成三类，这取决于最终态中存在多少带电介子。这三个类别是CC0pi、CC1pi和CCther，分别指0、1和&gt；1带电的事件。“CCther”示例包含最终状态为pi0的所有CC示例。因此，CCther样例的子集将包含主要来自pi0衰变的光子。本论文将提出一种新的选择方法，将CCther选择分为“有光子的CCther”和“无光子的CCther”。遴选的结果将被纳入T2K振荡分析框架，从而用于改善与此类事件相关的系统不确定性。对于将在本论文时间框架内开始的NOVA-T2K联合分析，了解CC与末态伽马的相互作用尤其重要。因此，该项目将利用近距离探测器的数据开发一组新的样品，并将它们纳入实验的振荡分析。

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.