Study of Neutrino Oscillations

斯坦福大学提出的这项研究旨在为中微子振荡这一自然基本特性的潜在原因提供新的理解。在过去的十年里，粒子物理学的一个意想不到的结果是发现了中微子有质量，当它们穿过空间或物质时，它们有能力从一种物质转变为另一种物质，而且这些转变的程度（混合角）惊人地大。中微子是我们宇宙的基本组成部分，与光子一起是数量最多的。然而，与其他基本成分相比，人们对中微子的了解很少，需要进一步的研究来理解宇宙学和天体物理学中的许多重大问题，探索粒子物理学标准模型之外的物理学，并解决我们宇宙中物质-反物质不对称的奥秘。提出的计划包括MINOS实验和计划用目前在费米实验室完成的中微子束进行离轴中微子实验。MINOS实验正处于建设的最后阶段。位于明尼苏达州北部苏丹矿的米诺斯探测器于2003年8月完成，并开始收集宇宙射线的数据。费米实验室的中微子束和其他相关建设工作预计将于2004年底完成，此后不久将开始使用加速器中微子进行数据采集。MINOS实验将显著提高我们对大气中微子能区中微子振荡参数的认识；将搜索亚优势振荡模式到电子和/或无菌中微子；并将观察到介子中微子消失的振荡行为，从而对该现象的振荡起源提供一个结论性的检验。这项研究的更广泛影响将发生在几个层面上：(a)了解物质是如何构成的以及自然力量如何将其塑造成无数可观察到的形式是一个长期存在的问题，科学家和非科学家都对此产生共鸣；(b)该研究计划提出了一系列问题，通过这些问题，学生和博士后不仅可以学习如何对物质的基本结构进行清晰的测试，还可以设计出进行测试的创新方法和工具。解决这些问题可以提供我们社会迫切需要的受过严格教育的年轻人；(c)该建议包括向更广泛的社区外展的内容。

The proposed research at Stanford University aims to provide new understanding of the underlying causes for a fundamental property of nature known as neutrino oscillations. One of the unexpected results in particle physics during the last decade has been the discovery that neutrinos have mass, that they have the ability to change from one species to another as they travel through space or matter, and that the extent of these transformations (mixing angles) is surprisingly large. Neutrinos are fundamental constituents of our universe and, together with photons are the most numerous. Yet, neutrinos are poorly understood compared to other fundamental constituents and further studies are required to understand many significant issues in cosmology and astrophysics, to probe physics beyond the Standard Model of particle physics, and to resolve the mystery of matter-antimatter asymmetry in our universe. The proposed program consists of the MINOS experiment and planning for an off-axis neutrino experiment with the neutrino beam currently being completed at Fermilab. The MINOS experiment is in its final stages of construction. The far detector of MINOS, located in the Soudan Mine in northern Minnesota was completed in August 2003 and has begun taking data on cosmic rays. The neutrino beam and other related construction efforts at Fermilab are expected to be complete by the end of 2004 and data taking with accelerator neutrinos should commence shortly thereafter. The MINOS experiment will significantly improve our knowledge of neutrino oscillation parameters in the atmospheric neutrino energy region; will search for subdominant oscillation modes into electron and/or sterile neutrinos; and will observe oscillatory behavior of muon neutrino disappearance, thus providing a conclusive test of the oscillation origin of that phenomenon. The broader impact of the research will occur at several levels: (a) Understanding how matter is constructed and how the forces of nature shape it into the myriad observed forms is a long standing question that resonates with scientists and non-scientists alike; (b) The research program poses a set of questions through which students and postdoctoral fellows will learn not only to frame crisp tests of the fundamental construction of matter, but also to devise innovative methods and tools for conducting them. Attacking such problems provides the rigorously educated young people that our society desperately needs; and (c) the proposal includes elements of outreach to the broader community.