Continuation of a Programme of Neutrino Factory Research and Development

在物理学目前已知的粒子种类中，中微子有三种类型：电子、μ子和τ子，可能是最有趣但最不为人所知的。中微子的质量很小，与物质的相互作用非常弱。迄今为止，所有粒子物理实验的结果都可以很容易地用20世纪60年代发展起来的粒子物理“标准模型”来解释：也就是说，除了少数几个研究中微子行为的实验中的一小部分结果。中微子在恒星和地球大气层中自然地不断产生。探测这些中微子的实验总是发现的中微子比产生的要少。那么他们去了哪里呢？有证据表明，这些“消失”的中微子已经改变或“振荡”成不同类型的中微子，而这些中微子是无法被探测到的。最近，人造中微子的实验也证明了类似的中微子振荡行为。对于自然界中的每一种粒子类型，都有相应的反粒子类型——反粒子加在一起被称为反物质。所以，对于这三种类型的中微子中的每一种，都有相应类型的反中微子。特别令人感兴趣的问题是，反中微子的振荡是否与中微子的振荡相同，还是反中微子的行为不同？这个问题被认为与以下事实有关：今天可观测到的宇宙几乎完全由物质组成，而140亿年前创造宇宙的大爆炸应该创造出等量的物质和反物质。反物质的去向之谜可以用中微子和反中微子振荡行为的不同来解释。这个问题只能通过使用高强度人造中微子束对中微子振荡进行超灵敏测量来回答。这项拟议研究的最终目标是在“中微子工厂”中产生有史以来人类创造的最强烈的中微子束。这些中微子束将以不同的角度穿过地球，到达世界上几个地方的不同探测器，从而在不同的距离上测量中微子振荡。这将使我们能够比以往更精确地确定中微子的性质，并使我们能够回答中微子和反中微子的振荡是否相同的基本问题。这应该能解开大爆炸时产生的反物质去了哪里的谜团，从而有助于解释我们今天所知道的宇宙的存在。

Of the species of particles currently known to physics, the neutrinos, which come in three types: electron, muon, and tau, are probably among the most intriguing but least understood. The neutrinos have tiny masses and interact with matter only very weakly. The results of all particle physics experiments to date have been readily explained by the 'Standard Model' of particle physics, developed in the 1960s: that is, except, for a small set of results from a select few experiments investigating the behaviour of neutrinos. Neutrinos are naturally produced continuously in stars and the earth's atmosphere. Experiments to detect these neutrinos have consistently found fewer neutrinos than are produced. So where did they go? There is evidence that these 'missing' neutrinos have changed or 'oscillated' into different types of neutrino, that are not detected. More recently, experiments involving man-made neutrinos have demonstrated similar neutrino oscillation behaviour. For each particle type in nature, there is a corresponding anti-particle type - the anti-particles together are known as anti-matter. So, for each of the three types of neutrinos, there is a corresponding type of anti-neutrino. Of particular interest is the question of whether the oscillations of anti-neutrinos are the same as those of neutrinos, or do the anti-neutrinos behave differently? This question is believed to be related to the fact that the observable universe today is composed almost entirely of matter, whereas the Big Bang which created the Universe 14 billion years ago, should have created equal amounts of matter and anti-matter. The mystery of where the anti-matter has gone could be explained by a difference in the oscillation behaviour of neutrinos and anti-neutrinos. This question can only be answered by making ultra-sensitive measurements of neutrino oscillations using high-intensity man-made beams of neutrinos. The ultimate goal of the proposed research is to produce the most intense beams of neutrinos ever created by man in a 'Neutrino Factory'. These beams of neutrinos will be directed at various angles through the Earth, to different detectors in several parts of the world, allowing the neutrino oscillations to be measured over different distances. This will allow the properties of the neutrinos to be determined far more precisely than ever before, and will allow us to answer the fundamental question of whether the oscillations of neutrinos and anti-neutrinos are the same or not. This should solve the puzzle of where the anti-matter created at the Big Bang has gone, and therefore help to explain the existence of the universe as we know it today.