A search for sub-dominant neutrino oscillations and measurement of the third neutrino mixing angle, theta13, with the Double Chooz experiment

通过 Double Chooz 实验寻找次主导中微子振荡并测量第三中微子混合角 theta13

• 批准号: PP/E005128/1
• 负责人: Jeffrey Hartnell
• 金额: $ 26.83万
• 依托单位: University of Sussex
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=PP%2FE005128%2F1
• 关键词: search; sub; dominant; neutrino; oscillations

What are neutrinos? Neutrinos are fundamental particles of Nature and despite being one of the most abundant particles in the Universe, the first observation of a neutrino was only 50 years ago. This highly elusive nature of neutrinos comes from the fact that they hardly ever interact with anything around them. Douglas Adams once described the chance of a neutrino interacting as it passes through the Earth as being 'roughly comparable to that of dropping a ball bearing at random from a cruising 747 and hitting, say, an egg sandwich'. Neutrinos weigh at least a 1/4 of a million times less than the electron, which is the next lightest particle and they could be much lighter still. It is widely believed that there are many fascinating facts about neutrinos yet to be discovered. This research proposal is about trying to understand and learn more about the special nature of neutrinos. There are three types of neutrino that have been directly seen but there could be more. In the last decade scientists have made a remarkable discovery: that a neutrino born as one type of neutrino can change in to one or both of the other two types of neutrino. But what's really interesting is that the neutrinos change, and then change back, repeatedly. This changing back and forth has been dubbed neutrino oscillations because it happens regularly like the swinging of the pendulum in a grandfather clock. Furthermore, it turns out that Nature only allows a certain fraction of the neutrinos to undergo these changes at any one time. Whether it's 50% of the neutrinos oscillating back and forth between the three types or just 5%, that is a fundamental parameter of Nature and it is the aim of this research proposal to measure that number. A strong source of neutrinos is a nuclear power station and you can detect the neutrinos from a long way away. The walls of the power station are almost completely transparent to the neutrinos and they pass straight through. You can imagine the neutrinos coming from the power station much like the light coming from inside a glass light bulb: it shines out in all directions. Vast numbers of neutrinos are emitted by the power station: around 1000 billion billion are produced every second. The experiment in this research proposal will be located about 1 km from the power station and it will detect only about one hundred neutrinos out of the billions passing through every 24 hours. If the neutrinos detected in this experiment were found to be changing type then it would be a tremendously important discovery. This is true not only because a fundamental constant of Nature would have been measured for the first time but it would also tell us whether neutrinos might hold the answers to a long outstanding mystery, namely where all the anti-matter in the Universe has gone. The Universe today is filled with matter and very little antimatter. But when it was formed in the Big Bang, equal amounts of matter and antimatter were made. Exactly what happened to all the antimatter is an intriguing puzzle and it is possible that by learning about neutrinos we will find the answer. If this experiment sees neutrinos from the power station oscillating then that will tell us whether it's possible for the behaviour of neutrinos and anti-neutrinos to be different. Thus, through studying neutrinos, we may have the beginnings of an answer to one of the big mysteries of the Universe.

什么是中微子？中微子是自然界的基本粒子，尽管它是宇宙中含量最丰富的粒子之一，但首次观测到中微子只是在50年前。中微子的这种高度难以捉摸的性质来自于它们几乎从来不与周围的任何东西相互作用的事实。道格拉斯·亚当斯曾将中微子在穿过地球时相互作用的几率描述为“大致相当于从一架巡航的波音747飞机上随机掉下一个滚珠，击中一个鸡蛋三明治”。中微子的重量至少比电子轻1/4，电子是仅次于最轻的粒子，而且还可能更轻。人们普遍认为，有许多关于中微子的有趣事实尚未被发现。这项研究计划是关于试图了解和了解更多关于中微子的特殊性质。有三种类型的中微子已经被直接看到，但可能还有更多。在过去的十年里，科学家们有了一项了不起的发现：一种中微子诞生时可以变成另外两种中微子中的一种或两种。但真正有趣的是，中微子会不断变化，然后又会反复变化。这种来回变化被称为中微子振荡，因为它经常发生，就像老爷钟中的钟摆一样。此外，事实证明，自然界在任何时候都只允许一定比例的中微子经历这些变化。无论是50%的中微子在三种类型之间来回振荡，还是只有5%，这都是自然界的一个基本参数，这项研究计划的目的是测量这个数字。中微子的一个强大来源是核电站，你可以从很远的地方探测到中微子。发电站的墙壁对中微子几乎是完全透明的，中微子直接穿过。你可以想象来自发电站的中微子，就像来自玻璃灯泡内部的光：它向四面八方照射。发电站释放出大量的中微子：每秒产生约1万亿个中微子。这项研究计划中的实验将位于距离发电站约1公里的地方，它将只探测到每24小时通过的数十亿中微子中的大约100个。如果在这次实验中检测到的中微子被发现正在改变类型，那么这将是一个非常重要的发现。这不仅是因为自然界的一个基本常数将首次被测量，而且它还将告诉我们，中微子是否可能掌握着一个长期悬而未决的谜团的答案，即宇宙中所有反物质都去了哪里。今天的宇宙充满了物质和极少的反物质。但当它在大爆炸中形成时，产生了等量的物质和反物质。所有反物质到底发生了什么是一个耐人寻味的谜题，通过学习中微子，我们可能会找到答案。如果这个实验看到发电站的中微子在振荡，那么它将告诉我们中微子和反中微子的行为是否有可能不同。因此，通过研究中微子，我们可能会开始解开宇宙中的一个大谜团。