Neutrino interactions in the GeV regime

我们的宇宙是由物质主导的，而不是反物质，然而物理定律似乎认为物质和反物质几乎是一样的。宇宙的物质支配被推测是由于在早期宇宙的极端条件下，破坏了电荷共轭和宇称的组合对称性的过程-在同时电荷反转和镜像反转下的对称性-的结果。这种对称性的破坏(CP破坏)确实存在于很小的水平上，并且已经在由夸克和反夸克组成的微观系统中被测量到。然而，这些效应被发现太小了十几个数量级，无法解释物质-反物质的不对称性。利用中微子可以找到CP破坏的新来源(轻子CP破坏，LCPV)。不同类型(味道)的中微子混合在一起，并且给定质量状态的味道组成在传播过程中可能不同，因此中微子振荡。在中微子振荡分析中，LCPV可以用中微子和相应的反中微子的振荡概率之差来识别。这分别是T2K和沙丘等当前和下一代实验的主要目标。中微子和反中微子可以由加速器产生，但我们只能用物质制造探测器，而不能用反物质。即使在标准模型中，中微子和反中微子与物质的相互作用也是不同的。为了检测非常微妙的LCPV特征，需要非常精确地理解这些相互作用。与核目标相关的影响是复杂的，导致重大不确定性。由于核效应在中微子-原子核相互作用中的重要性，最近两个世界领先的中微子相互作用实验Minerva和T2K进行了各种测量。为了对理解当前宇宙的物质-反物质不对称性的全球努力做出重大贡献，我提议在Minerva和T2K上进行横截面测量，系统地研究中微子相互作用，为未来的长基线中微子振荡实验提供关键输入。我还建议对沙丘高压气体时间投影室项目进行开创性的研发，这将显著提高LCPV测量的精度，并极大地促进沙丘科学的发展。

Our universe is dominated by matter over antimatter, and yet the laws of physics seemingly regards matter and antimatter almost the same. The matter dominance of the universe is conjectured to have resulted from processes violating the combined symmetry of charge conjugation and parity---a symmetry under simultaneous charge flip and mirror inversion---at extreme conditions in the early universe. The violation of this symmetry (CP violation) does exist at a small level and has been measured in microscopic systems that consist of quarks and antiquarks. However, the effects were found to be a dozen orders of magnitude too small to account for the matter-antimatter asymmetry. A new source of CP violation could be found with neutrinos (leptonic CP violation, LCPV). Different types (flavours) of neutrinos mix and the flavour composition of a given mass state can vary during propagation, hence neutrino oscillations. In neutrino oscillation analysis, LCPV can be identified with the difference between the oscillation probabilities of the neutrino and the corresponding antineutrino. This is the main goal of current and next-generation experiments such as T2K and DUNE, respectively.Neutrinos and antineutrinos can be generated by accelerators, but we can only make detectors out of matter, not antimatter. The interactions of neutrinos and antineutrinos with matter are different even in the Standard Model. To detect the very delicate LCPV signature, these interactions need to be understood very precisely. The effects associated with nuclear targets are complex, leading to significant uncertainties. Because of the importance of nuclear effects in neutrino-nucleus interactions, recently various measurements have been performed by MINERvA and T2K, the two world-leading experiments on neutrino interactions. To significantly contribute to the global effort in understanding the matter-antimatter asymmetry of the present universe, I propose to work on cross section measurements in MINERvA and T2K, to systematically study neutrino interactions to provide the crucial input for future long-baseline neutrino oscillation experiments. I also propose to work on pioneering R&D for the DUNE High Pressure Gas Time Projection Chamber project, which could significantly improve the precision of the LCPV measurements, and greatly add to the science of DUNE.