分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: This essay is intended to provide a brief description of the peculiar properties of neutrinos within and beyond the standard theory of weak interactions. The focus is on the flavor oscillations of massive neutrinos, from which one has achieved some striking knowledge about their mass spectrum and flavor mixing pattern. The experimental prospects towards probing the absolute neutrino mass scale, possible Majorana nature and CP-violating effects will also be addressed.
分类: 物理学 >> 核物理学 提交时间: 2016-09-18
摘要: Behind the observed pattern of lepton flavor mixing is a partial or approximate mu-tau flavor symmetry --- a milestone on our road to the true origin of neutrino masses and flavor structures. In this review article we first describe the features of mu-tau permutation and reflection symmetries, and then explore their various consequences on model building and neutrino phenomenology. We pay particular attention to soft mu-tau symmetry breaking, which is crucial for our deeper understanding of the fine effects of flavor mixing and CP violation.
分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: Given the best-fit results of six neutrino oscillation parameters, we plot the Dirac and Majorana unitarity triangles (UTs) of the 3\times 3 lepton flavor mixing matrix to show their real shapes for the first time. The connections of the Majorana UTs with neutrino-antineutrino oscillations and neutrino decays are explored, and the possibilities of right or isosceles UTs are discussed. In the neutrino mass limit of m_1 \to 0 or m_3 \to 0, which is allowed by current experimental data, we show how the six triangles formed by the effective Majorana neutrino masses \langle m\rangle_{\alpha\beta} (for \alpha, \beta = e, \mu, \tau) and their corresponding component vectors look like in the complex plane. The relations of such triangles to the Majorana phases and to the lepton-number-violating decays H^{++} \to \alpha^+ \beta^+ in the type-II seesaw mechanism are also illustrated.
分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: We carry out a new study of quark mass matricesMu(up-type) and Md(down-type) which are Hermitian and have four zero entries, and find a new part of the parameter space which was missed in the previous works. We identify two more specific four-zero patterns ofMu and Md with fewer free parameters, and present two toy flavor-symmetry models which can help realize such special and interesting quark flavor structures. We also show that the texture zeros of Mu and Md are essentially stable against the evolution of energy scales in an analytical way by using the one-loop renormalization-group equations.
分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: The Majorana nature of massive neutrinos will be crucially probed in the next-generation experiments of the neutrinoless double-beta (0ν2β) decay. The effective mass term of this process, ⟨m⟩ee, may be contaminated by new physics. So how to interpret a discovery or null result of the 0ν2β decay in the foreseeable future is highly nontrivial. In this paper we introduce a novel three-dimensional description of |⟨m⟩ee|, which allows us to see its sensitivity to the lightest neutrino mass and two Majorana phases in a transparent way. We take a look at to what extent the free parameters of |⟨m⟩ee| can be well constrained provided a signal of the 0ν2β decay is observed someday. To fully explore lepton number violation, all the six effective Majorana mass terms ⟨m⟩αβ (for α,β=e,μ,τ) are calculated and their lower bounds are illustrated with the two-dimensional contour figures. The effect of possible new physics on the 0ν2β decay is also discussed in a model-independent way. We find that the result of |⟨m⟩ee| in the normal (or inverted) neutrino mass ordering case modified by the new physics effect may somewhat mimic that in the inverted (or normal) mass ordering case in the standard three-flavor scheme. Hence a proper interpretation of a discovery or null result of the 0ν2β decay may demand extra information from some other measurements.