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

T2K是利用日本质子加速器研究中心（JPARC）生产的高强度介子-中微子束进行的长基线加速器中微子振荡实验。位于295公里外，离轴角度为2.5度的巨型超级神神探测器，一个装有11000个光敏探测器的50吨级水箱，可以看到600兆电子伏特的窄带波束。基线与能量的比值经过精细调整，用于研究所谓的大气中微子平方质量分裂的中微子振荡。通过一系列精细分割的固体闪烁体和时间投影室探测器，在中微子产生目标下游280 m处对光束进行采样。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。T2K使用了大约1E+21个质子在目标上的初始暴露，主要是在中微子模式下，获得了世界领先的结果。这些结果包括首次观测到介子-中微子束中电子-中微子的出现，首次对中微子cp -不变性违反相位（dCP）进行实验约束，以及利用介子-中微子和介子-反中微子消失对大气中微子的平方质量分裂和大气混合角进行高精度测量。VALOR拟合组在T2K物理开发中发挥了非常重要的作用：它领导了T2K内部的许多分析，并且在大多数已发表的振荡物理论文中做出了重大贡献。T2K现在已经进入了在反中微子模式下运行的高统计数据的新阶段，预计在不久的将来会有许多新的振荡结果，包括电子-反中微子外观的第一次测量，中微子混合中CP违反效应（sin（dCP）不等于零）的第一个有力证据，消失测量精度的提高和大气混合角八分仪的确定，以及对3-味范式的严格测试。Bench将加入VALOR，利用未来4年预计的非常高的统计数据，他将使用VALOR多样本3味分析的统一框架，同时领导实现上述所有物理目标。此外，Bench将研究执行近远探测器外推的替代方法，如果通过内部合作协议可以使用这种选择，他将通过结合T2K和NOvA结果来执行全球分析的努力做出重大贡献。

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.