Seed Corn Funding for Braidwood Project

布雷德伍德项目玉米种子资金

• 批准号: PP/D006848/1
• 负责人: Steven Biller
• 金额: $ 4.38万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=PP%2FD006848%2F1
• 关键词: Seed; Corn; Funding; Braidwood; Project

Neutrinos are governed by the weak nuclear force and form part of that fundamental class of particles called leptons. They come in three 'flavours' which are each paired with the electron, muon and tauon particles, respectively. We now know, however, that this classification is not as simple as it seems. Neutrinos also have mass (previously thought to be zero), but these masses do not directly correspond to those of the three neutrino flavours. Instead, a neutrino of a given flavour (like the electron-neutrino) can be viewed as a mixture of different neutrino mass states. This property allows neutrinos to apparently change or 'oscillate' between different types. A similar mixing phenomenon has long been known to exist among the quarks, though, at first glance, through a somewhat different mechanism. One of the many surprises is that the mixing amongst neutrinos is much larger than amongst the quarks. Nevertheless, theorists hope that the mixings in the two classes of particles can yet be related through some 'Grand Unified Theory' that brings together quarks and leptons, though the ability to do this straightforwardly will hinge on the value of a final mixing parameter which has not yet been determined. This parameter is known as 'theta13.' The oscillation relevant to theta13 may be affected as the neutrino state passes through matter and, if this were observed, it could be used to resolve the ordering of the neutrino mass states. Furthermore, it turns out that a third mixing angle would also allow some particle and anti-particle interactions to proceed at slightly different rates giving rise to 'CP-violation,' as for quarks. If the effect for leptons is large enough, it might explain the very existence of all the matter we see today. Therefore, the measurement of this third mixing angle and any associated CP-violation is an important next step. The first priority is to make a precise measurement of theta13, independent of these other possible effects. This is of fundamental interest in itself, and would also then allow other experiments (such as the planned T2K and NOvA projects) to look for CP violation and matter effects in the most sensitive and unambiguous manner. One of the best approaches to doing this is by looking for the apparent disappearance of anti-electron-neutrinos, produced in a nuclear reactor (due to their oscillations). Based on current experimental data, the distance scale over which this theta13 oscillation should occur is just under 2 kilometres from the reactor core. The challenge is that the size of the effect is expected to be only about 1 percent of the total, detectable neutrino flux - requiring a level of detection unprecedented for neutrino experiments. It is this measurement which the Braidwood project intends to carry out.

中微子受弱核力控制，是称为轻子的基本粒子类别的一部分。它们具有三种“风味”，分别与电子、μ子和τ子粒子配对。然而，我们现在知道这种分类并不像看起来那么简单。中微子也有质量（以前认为为零），但这些质量并不直接对应于三种中微子的质量。相反，给定味道的中微子（如电子中微子）可以被视为不同中微子质量状态的混合物。这一特性使得中微子能够在不同类型之间明显改变或“振荡”。人们早就知道夸克之间存在类似的混合现象，尽管乍一看是通过某种不同的机制实现的。许多令人惊讶的事情之一是中微子之间的混合比夸克之间的混合要大得多。尽管如此，理论学家希望这两类粒子的混合仍然可以通过某种将夸克和轻子结合在一起的“大统一理论”联系起来，尽管直接做到这一点的能力将取决于最终混合参数的值，该参数具有尚未确定。该参数称为“theta13”。当中微子状态穿过物质时，与 theta13 相关的振荡可能会受到影响，如果观察到这一点，它可以用来解决中微子质量状态的排序。此外，事实证明，第三个混合角也会允许一些粒子和反粒子相互作用以稍微不同的速率进行，从而导致“CP 破坏”，就像夸克一样。如果轻子的影响足够大，它可能解释我们今天看到的所有物质的存在。因此，测量第三个混合角和任何相关的 CP 破坏是重要的下一步。首要任务是对 theta13 进行精确测量，而不受其他可能影响的影响。这本身就具有根本意义，并且也将允许其他实验（例如计划中的 T2K 和 NOvA 项目）以最敏感和明确的方式寻找 CP 破坏和物质效应。做到这一点的最佳方法之一是寻找核反应堆中产生的反电子中微子的明显消失（由于其振荡）。根据目前的实验数据，发生θ13振荡的距离范围距离反应堆堆芯不到2公里。挑战在于，这种效应的大小预计仅为可检测中微子通量总量的 1% 左右，这需要中微子实验前所未有的检测水平。 Braidwood 项目打算进行的正是这种测量。