Neutrino Charge-Parity (CP) Symmetry Violation Search at the T2K Experiment

T2 K是一个长基线加速器中微子振荡实验，使用日本质子加速器研究综合体（JPARC）产生的高强度μ子中微子束。位于295公里外，离轴角为2.5度，巨大的超级神冈探测器，一个装有11,000个光敏探测器的50 kt水箱，看到了峰值为600 MeV的窄带光束。对基线能量比进行了微调，以研究所谓的大气中微子平方质量分裂的中微子振荡。该光束还采样280米的中微子生产目标下游的一系列细分固体闪烁体和时间投影室探测器。观察两个探测器之间中微子束的变化可以精确地提取振荡参数。T2 K使用大约1 E +21个质子的初始曝光在靶上获得了世界领先的结果，主要是在中微子模式下。这些结果包括有史以来第一次观察到电子中微子出现在μ中微子束，中微子CP不变性违反相位（dCP）的第一个实验约束和高精度测量大气中微子平方质量分裂和大气混合角使用μ中微子和μ反中微子消失。VALOR拟合组在T2 K物理开发中发挥了非常重要的作用：它领导了T2 K中的许多分析，并在大多数已发表的振荡物理论文中做出了实质性贡献。T2 K现在已经进入了一个以反中微子模式运行的高统计量的新阶段，预计在不久的将来会有许多新的振荡结果，包括首次测量电子-反中微子出现，中微子混合中CP破坏效应（sin（dCP）不等于零）的第一个强有力的证据，消失测量精度的提高和大气混合角八分圆的确定，Bench将加入VALOR，并在未来4年内使用预期的非常高的统计运行，他将使用VALOR多样本3-风味分析的统一框架，同时领导实现所有上述物理目标的努力。此外，Bench还将研究进行远近探测器外推的替代方法，如果通过相互合作协议可以提供这一选择，他将通过结合T2 K和NOvA的结果，为进行全球分析做出重大贡献。

T2K is a long-baseline accelerator neutrino oscillation experiment using the high-intensity muon-neutrino beam produced at Japan Proton Accelerator Research Complex (JPARC). Sitting 295 km away, at an off-axis angle of 2.5 degrees, the giant Super-Kamiokande detector, a 50-kt water tank instrumented with 11,000 photosensitive detectors, sees a narrow band beam peaked at 600 MeV. The baseline to energy ratio is finely tuned for studying neutrino oscillations at the so-called atmospheric neutrino squared-mass splitting. The beam is also sampled 280 m downstream of the neutrino production target by a series of finely segmented solid scintillator and time projection chamber detectors. Observing changes in the neutrino beam between the two detectors allows oscillation parameters to be accurately extracted. World-leading results were obtained by T2K using an initial exposure of around 1E+21 protons on target, mainly in neutrino mode. These results include the first ever observation of electron-neutrino appearance in a muon-neutrino beam, the first experimental constraints on the neutrino CP-invariance violating phase (dCP) and high-precision measurements of the atmospheric neutrino squared-mass splitting and atmospheric mixing angle using both muon-neutrino and muon-antineutrino disappearance. The VALOR fitting group played a very important role in the T2K physics exploitation: It led numerous analyses within T2K, and it had a substantial contribution in most published oscillation physics papers. T2K is now well into a new phase of high-statistics running in anti-neutrino mode and numerous new oscillation results are expected in the near future, including the first measurement of electron-antineutrino appearance, the first strong evidence for CP violating effects (sin(dCP) not equal to zero) in neutrino mixing, an improvement in the precision of disappearance measurements and determination of the atmospheric mixing angle octant, and stringent tests of the 3-flavour paradigm.Bench will join VALOR and, using the very high statistics runs expected in the next 4 years, he will lead the effort towards all above-mentioned physics goals simultaneously, using the unifying framework of the VALOR multi-sample 3-flavour analysis. In addition, Bench will investigate alternative methods to perform the near to far detector extrapolation and, should this option become available through inter-collaboration agreements, he will contribute substantially in efforts to perform a global analyses by combining T2K and NOvA results.