Can a non-unitary effect be prominent in neutrino oscillation measurements?

Subject to neutrino experiments, the mixing matrix of ordinary neutrinos can still have small vi-olation from unitarity. We introduce a quasi-unitary matrix to interpret this violation and propose a natural scheme to parameterize it. A quasi-unitary factor △QF is defined to be measured in neutrino oscillation exper-iments and the numerical results show that the improvement in experimental precision may help us figure out the secret of neutrino mixing.     

Can a non-unitary effect be prominent In neutrino oscillation measurements?

Subject to neutrino experiments, the mixing matrix of ordinary neutrinos can still have small vi-olation from unitarity. We introduce a quasi-unitary matrix to interpret this violation and propose a natural scheme to parameterize it. A quasi-unitary factor △QF is defined to be measured in neutrino oscillation exper-iments and the numerical results show that the improvement in experimental precision may help us figure out the secret of neutrino mixing.     

大亚湾反应堆中微子实验

中微子振荡是目前唯一超出粒子物理标准模型的新现象，它证明了中微子质量不为零，对粒子物理、天体物理与宇宙学均有非常重要的意义．在描述中微子振荡的6个参数中，目前仍有两个未知：交叉混合角θ13与CP相角δ．作者建议在大亚湾反应堆附近建设一个中微子实验站，测量混合角sin^2θ13，在90％的置信度下达到0．01的精度，较过去的实验提高近一个数量级．这将对中微子物理的未来发展提供方向性指导，特别是对理解宇宙中“反物质消失之谜”具有重要意义．     

大亚湾反应堆中微子实验

中微子振荡是目前唯一超出粒子物理标准模型的新现象,它证明了中微子质量不为零,对粒子物理、天体物理与宇宙学均有非常重要的意义.在描述中微子振荡的6个参数中,目前仍有两个未知：交叉混合角θ13与CP相角δ. 作者建议在大亚湾反应堆附近建设一个中微子实验站,测量混合角sin22θ13在90%的置信度下达到0.01 的精度,较过去的实验提高近一个数量级.这将对中微子物理的未来发展提供方向性指导,特别是对理解宇宙中“反物质消失之谜”具有重要意义.     

Neutrino anomaly and ν-nucleus interactions

A review of various calculations of the inclusive quasi-elastic reactions and pion production processes in neutrino reactions for various nuclei at intermediate energies relevant to solar, atmospheric and accelerator neutrinos is presented     

Quantum Mechanics of Neutrino Oscillations

We present a simple but general treatment of neutrino oscillations in the framework of quantum mechanics, using plane waves and intuitive wave packet principles when necessary. We attempt to clarify some confusing statements that have recently appeared in the literature.     

后中微子振荡发现的实验进展与展望

2015年诺贝尔物理学奖授予了发现中微子振荡也就是中微子有质量的实验。这个发现是至今为止,粒子物理标准模型——这一得到广泛实验验证的理论中唯一指明存在新物理的明显证据。文章将介绍中微子振荡发现以后主要的中微子实验物理目标、采用的探测技术、实验状况及其未来展望。     

Atmospheric neutrinos and discovery of neutrino oscillations

Neutrino oscillation was discovered through studies of neutrinos produced by cosmic-ray interactions in the atmosphere. These neutrinos are called atmospheric neutrinos. They are produced as decay products in hadronic showers resulting from collisions of cosmic rays with nuclei in the atmosphere. Electron-neutrinos and muon-neutrinos are produced mainly by the decay chain of charged pions to muons to electrons. Atmospheric neutrino experiments observed zenith-angle and energy dependent deficit of muon-neutrino events. Neutrino oscillations between muon-neutrinos and tau-neutrinos explain these data well. Neutrino oscillations imply that neutrinos have small but non-zero masses. The small neutrino masses have profound implications to our understanding of elementary particle physics and the Universe. This article discusses the experimental discovery of neutrino oscillations.     

Bounds on neutrino mixing with exotic singlet neutrinos

We examine the effects of mixing induced non-diagonal light-heavy neutrino weak neutral currents on the amplitude for the process (with a=e, μ or τ). By imposing constraint that the amplitude should not exceed the perturbative unitarity limit at high energy , we obtain bounds on light-heavy neutrino mixing parameter sin² where is the mixing angle. In the case of one heavy neutrino (mass mξ) or mass degenerate heavy neutrinos, for Λ=1 TeV, no bound is obtained for mξ<0.50 TeV. However, sin² ≤3.8 × 10⁻⁶ for mξ=5 TeV and sin ≤6.0 × 10⁻⁸ for mξ=10 TeV. For Λ=∞, no constraint is obtained for mξ<0.99 TeV and sin² ≤3.8 × 10⁻² (for mξ=5 TeV) and sin² ≤9.6 × 10⁻³ (for mξ=10 TeV).     

Solar Neutrino Problem in Seesaw Model

A specific texture for the Dirac and Majorana mass matrices in the seesaw model leading to a pair of almost degenerate neutrinos is discussed. This texture can be obtained by imposing a global U(1) symmetry. This model could solve the solar neutrino problem through the MSW mechanism and offer the hot component of the dark matter of the universe which requires Σm_vi = 7 eV.     

中微子物理

近十几年来积累的数据表明,有相当数量的太阳中微子流在从太阳到地球探测器的漫长旅程中丢失了。最新的大气中微子实验结果指出,宇宙射线引起的大气中νμ与νｅ的比例不是原有理论预言的２：１,而是接近１：１,而且发现从上而下的νμ数目比从下而上的多,νｅ的数量却基本不变,这两种现象可能是源于中微子振荡或其他的机制,然而这些机制并没有包含在２０世纪的最成功的理论－最小标准模型中。换言之,要合理解释反观测到的中     

Bi-large Neutrino Mixing See-Saw Mass Matrix with Texture Zeros and Leptogenesis

We study constraints on neutrino properties for a class of bi-large mixing See-Saw mass matrices with texture zeros and with the related Dirac neutrino mass matrix to be proportional to a diagonal matrix of the form diag(ε,1,1). Texture zeros may occur in the light (class a) or in the heavy (class b) neutrino mass matrices. Each of these two classes has 5 different forms which can produce non-trivial three generation mixing with at least one texture zero. We find that two types of texture zero mass matrices in both class a and class b can be consistent with present data on neutrino masses and mixing. None of the neutrinos can have zero masses and the lightest of the light neutrinos has a mass larger than about 0.046 eV for class a and 0.0027 eV for class b. In these models although the CKM CP violating phase vanishes, the non-zero Majorana phases can exist and can play an important role in producing the observed baryon asymmetry in our universe through leptogenesis mechanism. The requirement of producing the observed baryon asymmetry can further distinguish different models and also restrict the See-Saw scale to be in the range of 10¹²～10¹⁵ GeV. We also discuss RG effects on V₁₃.     

中微子振荡实验——超出标准模型的实验检验（Ⅰ）

文章总结了中微子振荡实验在历史和现状,介绍了几个太阳中微子丢失实验的结果和几个大气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,文章还介绍了21世纪初研究中微子振荡和若干重要实验,噬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。     

2002年度诺贝尔物理奖

对2002年度的诺贝尔物理奖和中微子天文学以及一些相关的有趣问题作了比较详细的介绍。介绍了太阳中微子短缺之谜以及长达三四十年的奋斗历程;SN1987A中微子的发现以及最近太阳中微子短缺之谜的解决。还介绍了X射线天文学的发现和进展。现在,X射线天文学已经发展成为可与光学天文学、射电天文学媲美的一门举足轻重的学科。