Seed Corn Funding for Braidwood Project

中微子受弱核力的支配，形成了称为轻子的基本粒子类别的一部分。它们有三种“味道”，分别与电子粒子、介子粒子和陶子粒子配对。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(以前被认为是零)，但这些质量并不直接对应于三种中微子的质量。相反，一种特定性质的中微子(如电子中微子)可以被视为不同中微子质量状态的混合物。这一特性允许中微子在不同类型之间明显地改变或“振荡”。虽然乍一看，夸克之间存在着一种略有不同的机制，但人们早就知道夸克之间存在类似的混合现象。其中一个令人惊讶的是，中微子之间的混合比夸克之间的混合要大得多。然而，理论家们希望这两类粒子的混合仍能通过某种将夸克和轻子结合在一起的“大统一理论”联系在一起，尽管能否直接做到这一点将取决于尚未确定的最终混合参数的值。此参数称为‘theta13’。当中微子状态通过物质时，与中微子13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有序性。此外，事实证明，第三个混合角也将允许一些粒子和反粒子的相互作用以略有不同的速度进行，从而导致对夸克的“CP破坏”。如果轻子的影响足够大，它可能解释了我们今天所看到的所有物质的存在。因此，测量这第三个混合角和任何相关的CP破坏是重要的下一步。当务之急是准确地测量温度，而不考虑其他可能的影响。这本身就是最重要的，也将允许其他实验(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。要做到这一点，最好的方法之一是寻找在核反应堆中产生的(由于它们的振荡)反电子中微子的明显消失。根据目前的实验数据，这种振荡发生的距离距离反应堆堆芯不到2公里。挑战是，这种效应的大小预计只占可检测到的中微子通量总量的1%左右--这需要达到中微子实验中前所未有的检测水平。布雷德伍德项目打算实施的正是这一措施。

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.