中微子几何混合模型与轻子和重子数产生

在这一报告中将报告我和BABU教授合作的在hep-ph/0507217一文中有关中微子混合研究结果. 目前中微子实验数据所决定的混合角可归结为几何混合状况:sin²θ₁₂=1/3,sin²θ₂₃=1/2, 和sin²θ₁₃=0. 我们在这一工作中建立了能实现这一几何混合的可重整化模型. 模型以非阿贝尔非连续群A₄为描述中微子不同代混合的对称性. 这类模型对中微子质量有很强的限制. 而且能很自然地由轻子数破坏产生重子不对称的实验观测值. 很有趣的是这类模型中出现在轻子不守恒和无中微子双beta衰变中的相位是一样的.     

在中微子振荡中的CP破坏

讨论了中微子味混合与中微子振荡的理论,定量地研究了在中微子振荡中的CP破坏效应.在一类超对称模型中,计算了真空中中微子振荡几率和 CP破坏效应.     

中微子六十年

 中微子质量的测量方法有直接和间接两种.通常的探测器是探测不到的中微子,但可由能动量守恒以及事例终态的重建得出事例的丢失质量,由此得出中微子质量,这种方法称为直接法.从β衰变的电子能谱确定电子中微子质量用的就是此法.μ子族中微子和τ子族中微子质量也是用这种方法得出的.此外,还有采用中微子振荡和双β衰变法,这些是间接法.1)β衰变的能谱测量:β衰变中发射的电子能谱具有形状（如果电子中微子具有质量m_v）.     

中微子物理若干前沿问题

 在过去的几年间,大量的实验结果已经表明中微子有非零质量以及轻子味混合。这一进展为我们打开了一个全新的值得探索的基本粒子世界。关于中微子我们已经知道了多少,我们想要发现什么?本文将从理论与唯象的观点进行阐述。目前中微子物理的前沿问题主要包括:中微子真的发生味转化吗?有几代中微子?存在惰性中微子吗?中微子的质量是多少?中微子是马约拉纳粒子还是狄拉克粒子?轻子味混合矩阵的混合角有多大?轻子味混合矩阵包含CP破坏位相吗?如果包含,那么在中微子振荡和无中微子双β衰变中,这些位相会导致可探测的CP破坏效应吗?     

跷跷板模型中三阶中微子混合矩阵的幺正性破坏

对标准模型的一种简单扩充就是引入n个重的右手中微子且保持其SU(2)_L×U(1)_Y规范对称性. 通过对角化(3+n)×(3+n)阶中微子质量矩阵, 得到关于ν_e, ν_μ和ν_τ的有效 质量矩阵的精确的解析表达式. 结果表明, 在轻子带电弱流中出现的3×3中微子混合矩阵V必须不是严格幺正的. 如果通过跷跷板机制产生正确的轻的中微子的质量标度, 那么V的幺正性破坏的程度非常小, 几乎可以忽略. 类似的结论同样可以在第二类跷跷板模型中得到.     

“太阳中微子失踪案和中微子振荡”一文中的若干问题

 《现代物理知识》2002年第一期和第二期连载了彭秋和先生的文章:“太阳中微子失踪案和中微子振荡”。这篇文章系统地介绍了太阳中微子问题的来龙去脉,内容丰富,可读性强。然而文中对中微子质量和中微子振荡的叙述有几处严重失实。     

中微子质量矩阵和中微子转换矩阵间的一种可能的关系

我们探讨了以ν_e,ν_μ,ν_τ为基的, 具有一种新的对称性的中微子质量矩阵M. 首先在没有T(时间)破坏的前提下, 假定该质量矩阵具有一个简单的三参数形式. 这一矩阵确定了3种中微子的质量m₁, m₂, m₃以及使M对角化的转换矩阵U. 因为无T破坏的U给出3个可测量参数s₁₂, s₂₃, s₁₃, 我们的形式用3个参数表示6个可测量的物理量, 其结果与实验数据符合得很好. 更精确的测量将对模型给出严格的检验, 并确定这3个参数的值. 本文还推广讨论了包含T破坏的情况.     

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。     

Neutrino masses and lepton-flavor-violating τ decays in the supersymmetric left-right model

In the supersymmetric left-right model, the light neutrino masses are given by the Type-Ⅱ seesaw mechanism. A duality property of this mechanism indicates that there exist eight possible Higgs triplet Yukawa couplings which result in the same neutrino mass matrix. In this paper, we work out the one-loop renormalization group equations for the effective neutrino mass matrix in the supersymmetric left-right model. The stability of the Type-Ⅱ seesaw scenario is briefly discussed. We also study the lepton-flavor-violating processes (τ→ μγ and τ→eγ) by using the reconstructed Higgs triplet Yukawa couplings.     

等效质量模型中的重子质量谱

在等效质量模型框架下,考虑线性禁闭和一阶微扰相互作用的贡献并通过拟合$ \mathrm{p} $、$ \mathrm{n}$、$\Lambda$和$ \Delta $的质量来得到模型参数。发现,等效质量模型能够较好地给出符合实验的重子质量谱。而禁闭强度$D$、强耦合常数$\alpha_{\rm{s}}$以及夸克质量因子$f$与微扰强度$C$之间都存在关联,并能够很好地用解析公式逼近。除此之外,单胶子交换相互作用的色磁部分在重子质量谱中起着重要作用,从而使自旋$J=1/2$和3/2的重子之间的质量差最高达到300 MeV。为了更好地描述超子质量,对于包含奇异夸克的一对夸克间的相互作用我们进一步采用不同的强耦合常数,其具体的模型参数通过拟合$ \Sigma $和$ \Xi $的质量得到。基于本工作得到的等效质量模型参数组,能够更好地描述$ \mathrm{ud}$夸克物质团、奇异子以及致密星。     

Friedberg-Lee neutrino model with μ-τ reflection symmetry

In this letter, we make an attempt to embed the μ-τ reflection symmetry (which predicts maximal atmospherical mixing angle and Dirac CP phase) in the Friedberg-Lee neutrino model (which employs a translational flavor symmetry and keeps one neutrino mass vanishing) and study the consequences of such a combination.     

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.     

Neutrino masses and flavor mixing

We study a model for the mass matrices of the leptons, based on texture zero elements. We are able to relate the mass eigenvalues of the charged leptons and of the neutrinos to the mixing angles, and can predict the masses of the neutrinos. We find a normal hierarchy—the masses are 0.005 eV, 0.01 eV and 0.05 eV. Predictions for the double beta decay and the reactor neutrino experiments are made.     

Neutrino Mixing in the BLMSSM

Abstract In recent years, a nonzero value for the neutrino mixing angle θ13 has been successively measured by the international famous reactor oscillation experiments, which is greater than 5 standard deviations. Our study is in the framework of the MSSM, where baryon and lepton numbers are local gauged symmetries （BLMSSM）. This model can generate three tiny neutrino masses at the tree level through TeV scale seesaw mechanism. In our paper, we analyze the neutrino masses and their corresponding mixing angles with a ＂top-down＂ method, assuming neutrino mass spectrum with normal ordering （NO） and inverted ordering （IO）.     

Neutrino masses and mixing in supersymmetric theories

It has been known for sometime that supersymmetric theories with R-parity violation provide a natural framework where small neutrino masses can be generated. We discuss neutrino masses and mixing in these theories in the presence of trilinear lepton number violating couplings. It will be shown that simultaneous solutions to solar and atmospheric neutrino problems can be realized in these models.     

A Model of Fermion Masses and Flavor Mixings with Family SymmetrySU(3)\otimes U(1)

The family symmetrySU}(3)\otimes U(1) is proposed to solve flavor problems about fermion masses and flavor mixings. It is breaking is implemented by some flavon fields at the high-energy scale. In addition a discrete group Z₂ is introduced to generate tiny neutrino masses, which is broken by a real singlet
scalar field at the middle-energy scale. The low-energy effective theory is elegantly obtained after all of super-heavy fermions are integrated out and decoupling. All the fermion mass matrices are regularly characterized by four fundamental matrices and thirteen parameters. The model can perfectly fit and account for all the current experimental data about the fermion masses and flavor mixings, in particular, it finely predicts the first generation
quark masses and the values ofθ₁₃^l and J_CP^l in neutrino physics. All of the results are promising to be tested in the future experiments.     

Correlation of normal neutrino mass ordering with upper octant of θ_(23) and third quadrant of δ via RGE-induced μ-τ symmetry breaking

The recent global analysis of three-flavor neutrino oscillation data indicates that the normal neutrino mass ordering is favored over the inverted one at the 3σ level, and the best-fit values of the largest neutrino mixing angle θ_(23) and the Dirac CP-violating phase δ are located in the higher octant and third quadrant, respectively. We show that all these important issues can be naturally explained by the μ-τ reflection symmetry breaking of massive neutrinos from a superhigh energy scale down to the electroweak scale owing to the one-loop renormalization-group equations(RGEs) in the minimal supersymmetric standard model(MSSM). The complete parameter space is explored for the first time in both the Majorana and Dirac cases, by allowing the smallest neutrino mass m1 and the MSSM parameter tanβ to vary within their reasonable regions.     

A Model of Fermion Masses and Flavor Mixings with Family Symmetry SU(3)U(1)

The family symmetry SU(3)U(1) is proposed to solve flavor problems about fermion masses and flavor mixings.It is breaking is implemented by some flavon fields at the high-energy scale.In addition a discrete group Z 2 is introduced to generate tiny neutrino masses,which is broken by a real singlet scalar field at the middle-energy scale.The low-energy effective theory is elegantly obtained after all of super-heavy fermions are integrated out and decoupling.All the fermion mass matrices are regularly characterized by four fundamental matrices and thirteen parameters.The model can perfectly fit and account for all the current experimental data about the fermion masses and flavor mixings,in particular,it finely predicts the first generation quark masses and the values of θ l 13 and J l CP in neutrino physics.All of the results are promising to be tested in the future experiments.     

Pair production of right-handed neutrinos in the left-right twin Higgs model at ILC and LHC

In the framework of the left-right twin Higgs model, we study pair production of the right-handed neutrinos at the International Linear Collider (ILC) and the CERN Large Hadron Collider (LHC). Our numerical results show that the production cross section of the process e+e→N N is at the level of several tens fb at the ILC. However, the resonance production cross section can be significantly enhanced to the order of pb. The pair production cross section for the right-handed neutrinos is the level of several h...