β衰变之谜简史

有关中微子的研究是现在物理学界的一个重要课题,也曾多次获得过诺贝尔物理学奖,然而这一切的起源却应归功于β衰变连续能谱的证实,β衰变连续能谱曾是困扰物理学界20多年的谜题,为了揭示这一谜题埃利斯和伍斯特做了大量的实验研究,然而他们的贡献却鲜为人知.     

β衰变的历史概述

β衰变的研究是一个探究物质深层物理原理的过程.它始于β放射性的研究,引导人类对物质的认识开始从原子深入到原子核内部.其能谱的测量,导致了泡利的中微子假设.在此基础上,费米第一次提出了关于β衰变的唯象理论并提出了弱相互作用的概念.此后发展出弱相互作用的中间玻色子理论,使得人类对物质的认识深入到核子内部,促进了电弱统一理论的发展,最终促成了标准模型的完成.文章回顾了β衰变这一横亘整个20世纪的重要物理学事件,对β衰变的研究历史中的关键事件进行了分析和介绍,对理解现代物理学中的标准模型的建立和发展有重要意义.     

在LHC上寻找希格斯粒子

 大型强子对撞机(Large Hadron Collider,简称LHC)2010 年3 月开始运行,对撞能量为7TeV,这是设计能量14 TeV 的一半。瞬时亮度从10²⁷cm^-2s^-1迅速上升,2010 年底达到10³²cm^-2s^-1,2011 年底达到10³³cm^-2s^-1,积分亮度有5/fb, 超过原来的预期。LHC 进入出成果阶段。     

论中微子超光速与洛伦兹对称性破坏以及质量产生

 2011 年9 月位于意大利GranSasso 地下实验室的OPERA 中微子实验国际合作组发表了一篇预印本(T. Adam et al. (OPERA Collaboration),“Measurement of the Neutrino Velocity with theOPERA Detector in the CNGS beam”,arXiv:1109.4897v2),声称测到了来自730 千米外的欧洲核子中心 CERN 通过高能质子打靶产生μ中微子束流的超光速现象,这一消息很快在 Nature和Science 等新闻媒体上报道,激起了公众的极大好奇。     

中微子的螺旋度反转

庆祝著名物理学家Maurice Goldhaber百岁生日的文章,该文的作者是Maurice Goldhaber本人(前美国布鲁克海文国家实验室主任)和他的儿子Alfred Scharff Goldhaber(美国纽约大学石溪分校杨振宁理论物理研究所教授).在文章中,Goldhaber父子阐明了粒子的螺旋度和手征性     

中微子质量和中微子振荡实验

本文介绍中微子质量测量的历史和现状。介绍太阳中微子丢失实验的结果和大气 μ中微子丢失实验结果。这些结果表明存在中微子振荡 ,即中微子具有质量。它是超出标准模型的信号。本文还介绍了 2 1世纪初研究中微子振荡的若干重要实验 ,例如长基线中微子振荡实验以及建造 μ子贮存环来产生高能电子中微子束进行中微子振荡的实验以及测量中微子振荡时的CP破坏的设想。     

Earthquake forecast via neutrino tomography

We discuss the possibility of forecasting earthquakes by means of (anti)neutrino tomography. Antineutrinos emitted from reactors are used as a probe. As the antineutrinos traverse through a region prone to earthquakes, observable variations in the matter effect on the antineutrino oscillation would provide a tomography of the vicinity of the region. In this preliminary work, we adopt a simplified model for the geometrical profile and matter density in a fault zone. We calculate the survival probability of electron antineutrinos for cases without and with an anomalous accumulation of electrons which can be considered as a clear signal of the coming earthquake, at the geological region with a fault zone, and find that the variation may reach as much as 3% for ν_e emitted from a reactor. The case for a ν_e beam from a neutrino factory is also investigated, and it is noted that, because of the typically high energy associated with such neutrinos, the oscillation length is too large and the resultant variation is not practically observable. Our conclusion is that with the present reactor facilities and detection techniques, it is still a difficult task to make an earthquake forecast using such a scheme, though it seems to be possible from a theoretical point of view while ignoring some uncertainties. However, with the development of the geology, especially the knowledge about the fault zone, and with the improvement of the detection techniques, etc., there is hope that a medium-term earthquake forecast would be feasible.     

Effects of the δ meson on the direct Urca processes in neutron stars

In the framework of the relativistic mean field theory, the effects of the δ meson on the direct Urca (DURCA) processes are investigated. In a neutron star, the DURCA processes involving nucleons, Λ and Ξ^- can take place while the process involving the Ξ⁰ can not. With the inclusion of the δ meson, the threshold densities for the DURCA processes become lower. With the δ included, the threshold neutron star mass for the DURCA process among nucleons and electrons becomes smaller while the threshold masses for the processes involving hyperons become larger. When the δ meson is included, the total neutrino emissivity remarkably increases in the density range of 0.32--0.41 fm^-3. The total neutrino luminosity increases with the neutron star mass first and then decreases. The neutrino luminosity gets larger with the inclusion of the δ meson. The cooling of the EXO0748-676 is sensitive to the isovector scalar interaction.     

无中微子双β衰变相关的中微子势（英文）

介绍了在双β衰变中的闭合近似下的原子核矩阵元,并在此基础上研究了无中微子双β衰变的中微子势部分及统计性质。分析结果显示,费米型和伽莫夫-泰勒型矩阵元部分贡献了几乎相等的正值,并且费米型部分一般比伽莫夫-泰勒型部分的贡献稍大,而张量部分的贡献虽小但不可忽略,其中有少量矩阵元为负。阐明了无中微子双β衰变的中微子势中费米型、伽莫夫-泰勒型及张量部分大于零矩阵元的关联。该统计结果粗略地揭示了这些组份对原子核矩阵元的贡献。Nuclear matrix element in double beta decay under the closure approximation is outlined, in which neutrino potential for neutrinoless double beta decay is studied with focusing on its statistical property. It is shown from the analysis that Fermi and Gamow-Teller parts provide almost the same positive values with the Fermi part slightly larger than the Gamow-Teller part in general, while the tensor part includes small but non-negligible positive and negative values. Positive correlation of the values between Fermi, Gamow-Teller, and tensor parts has been clarified. The statistics provides a gross view of understanding amplitude of constitutional components of the nuclear matrix element.