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，尽管它是宇宙中最丰富的粒子之一，但对中微子的首次观测却是在 50 年前。中微子这种高度难以捉摸的性质来自于它们几乎不与周围的任何物体相互作用。道格拉斯·亚当斯 (Douglas Adams) 曾经将中微子穿过地球时相互作用的几率描述为“大致相当于从巡航的 747 客机上随机掉落滚珠轴承并击中鸡蛋三明治”。中微子的重量至少比电子轻一百万分之一，电子是第二轻的粒子，而且中微子的重量可能还轻得多。人们普遍认为，关于中微子还有许多令人着迷的事实有待发现。这项研究计划旨在尝试了解和更多地了解中微子的特殊性质。人们直接观测到的中微子有三种类型，但可能还有更多。在过去的十年中，科学家们有了一个了不起的发现：作为一种中微子诞生的中微子可以转变为其他两种类型的中微子中的一种或两种。但真正有趣的是中微子不断变化，然后又变回来。这种来回变化被称为中微子振荡，因为它像老钟中钟摆的摆动一样定期发生。此外，事实证明，大自然只允许一部分中微子在任何时候经历这些变化。无论是 50% 的中微子在三种类型之间来回振荡，还是只有 5%，这都是自然的一个基本参数，本研究计划的目的就是测量这个数字。核电站是中微子的重要来源，您可以从很远的地方检测到中微子。发电站的墙壁对中微子来说几乎是完全透明的，它们直接穿过。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一样：它向各个方向发光。发电站释放出大量中微子：每秒产生约 10000 亿个中微子。该研究计划中的实验将位于距离发电站约 1 公里的地方，每 24 小时将检测到数十亿个中微子，而其中仅检测到约 100 个中微子。如果在这个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。这是真的，不仅因为第一次测量了自然的基本常数，而且它还能告诉我们中微子是否可能解答一个长期悬而未决的谜团，即宇宙中所有反物质都去了哪里。今天的宇宙充满了物质，而反物质却很少。但当它在大爆炸中形成时，就产生了等量的物质和反物质。所有反物质究竟发生了什么是一个有趣的谜题，通过了解中微子我们可能会找到答案。如果这个实验看到来自发电站的中微子振荡，那么这将告诉我们中微子和反中微子的行为是否可能不同。因此，通过研究中微子，我们可能开始解答宇宙的一大谜团。