Leptonic CP-Violation with ESSνSB: Design and Simulations of the 4-Horn Target Station

基于物质和反物质在基本粒子尺度上的微小差异，即所谓的电荷宇称（CP-）违逆，科学家们认为它们之间存在一些微妙的不对称，并且在大爆炸之后不久，这导致了一个由物质主导的宇宙。目前的问题是没有观察到足够的cp -违逆，而且标准模型（SM）也没有足够的预测来解释观察到的不对称性。所谓的“中微子振荡”现象令人信服地表明，中微子确实有质量，这与SM假说相矛盾。最近的反应器实验结果表明，第3个混合角θ13高于先前定义的标准值，达到了~ 9°，为发现和测量狄拉克轻子CP违背角δ_CP的非零值打开了新的窗口。此外，T2K实验最近报告了δ_CP的新结果，在99.7% （3σ）置信度下，他们不赞成几乎一半的可能值。鉴于这些新发现，迫切需要提高当前长基线探测器的探测灵敏度，并进行关键修改，将远端探测器置于第二个振荡最大值，而不是第一个振荡最大值。目前计划中的许多探测器都是使用“强”中微子束的探测器，如美国的DUNE，日本的T2HK和欧洲的ESSνSB。虽然美国和日本实验的设计目标是测量第一振荡，但ESSvSB将测量第二振荡最大值，与其他两个实验相比，导致对CP -违和的灵敏度显着更高。在解决ESSνSB探测器的设计之前，必须精确研究几个技术挑战。其中，目标站的设计和物理以及中微子束在这个项目阶段被认为是最优先考虑的。自2019年9月起，UHH代表德国作为准成员参与该项目。本dfg提案的战略目标是继续并扩大这一独特贡献。这一贡献将在IEP-UHH的中微子群内继续进行。该提案的具体目标是：1-优化强子收集器（喇叭）设计，以增加探测器上的电荷电流，CC，事件，从而提高中微子束的特性；通量和剖面。2 -在ESSνSB目标站的不同部位和屏蔽层进行全辐射、能量沉积和激活计算。3-定义目标站及其内部组件的基线设计，这些将在第一阶段结束时的esso sb CDR中引入，随后在TDR中引入。我坚信，通过UHH继续参与这样一个独特的项目，无疑将加强德国中微子物理界，特别是UHH在国内和国际上在这一领域的作用。

Based on the tiny differences in how matter and antimatter behave at the scale of elementary particles, known as charge-parity, CP-, violation, scientists believe that there is some subtle asymmetry between them, and that soon after the Big Bang, this led to a universe dominated by matter. The current problem is that not enough CP-violation has been observed, and that the Standard Model (SM) also does not predict enough to explain the observed asymmetry. The so-called “neutrino oscillations” phenomenon convincingly indicates that neutrinos do have mass, contradicting the SM hypotheses. Recent results from reactor experiments have shown that the third mixing angle, θ13 , is higher than its previously defined standard value, with a value of ~ 9°, opening a new window for discovering and measuring a nonzero value of the Dirac leptonic CP violating angle, δ_CP. Moreover, the T2K experiment has recently reported new results on the δ_CP, where they disfavored almost half of its possible values at the 99.7% (3σ) confidence. In the light of these new findings, an urgent need raised to improve the detection sensitivity of the current long-baseline detectors, with a key modification to place the far detectors at the second, rather than the first, oscillation maximum. Many of the presently planned detectors are the ones that use “intense” neutrino beams, such as DUNE in the USA, T2HK in Japan and ESSνSB in Europe. While the design of the US and Japanese experiments aim for measurement at the first-, the ESSvSB will measure at the second- oscillation maximum, leading to a significantly higher sensitivity to CP‐violation compared to the other two experiments. Several technological challenges must be precisely studied before addressing the design of the ESSνSB detector. Among these, the design and physics of the target station and the neutrino beam considered highest priority at this phase of the project. UHH represents Germany in the project, as an associate member, since September 2019. The strategic objective of this DFG-proposal is to continue and extend this unique contribution. This contribution will be continued within the neutrino group of the IEP-UHH. The specific objectives of the proposal are: 1- Optimization of the hadron-collector (horn) design in order to increase the charge current, CC, events at the detector, hence the neutrino beam characteristics; flux and profile. 2 -Perform full radiation, energy deposition and activation calculations in the different parts and shields of the ESSνSB target station. 3- Define the baseline design for the target station and its internal components, which will be introduced in the ESSνSB CDR at the end of phase-I, and later in the TDR.I strongly believe that continuing such involvement through the UHH in such unique project will undoubtedly reinforce the role that the German neutrino physics community, in general, and that of the UHH, in particular, plays, nationally and internationally, in this field.