CP violation and neutrino oscillations

We review the basic mechanisms of neutrino mass generation and the corresponding structure of the lepton mixing matrix. We summarize the status of three-neutrino oscillation parameters as determined from current observations, using state-of-the-art solar and atmospheric neutrino fluxes, as well as latest experimental data as of September 2007. We also comment on recent attempts to account for these results and to understand flavour from first principles. We discuss extensively the prospects of probing the strength of CP violation in two near term accelerator neutrino oscillation experiments, T2K and , as well as possible extensions such as T2KK and a second large off-axis detector near the detector. We also briefly discuss the possibility of probing the effect of Majorana phases in future neutrinoless double beta decay searches and discuss other implications of leptonic CP violation such as leptogenesis. Finally we comment on the issue of robustness of the current oscillation interpretation and possible ways of probing for non-standard neutrino interactions in precision oscillation studies.     

Matter effects for solar neutrino oscillations

Possible solar neutrino oscillations are reviewed in the two-neutrino case taking into account the effect of coherent forward scattering when neutrinos travel through the sun and earth. As recently pointed out by Mikheyev and Smirnov this effect can induce a large suppression of the solar ν_e flux for values of Δm ² around 10^?4–10^?8 eV² even for small values of the mixing angle. It also may cause substantial modifications of the solar neutrino spectrum shape. All this may be used for determining Δm ² and sin² 2θ in a large domain from the experimental results of the chlorine, gallium, indium and heavy water detectors.     

Spontaneous parity violation and minimal Higgs models

In this paper we present a model for the spontaneous breaking of parity with two Higgs doublets and two neutral Higgs singlets which are even and odd under -parity. The condition can be satisfied without introducing bidoublets, and it is induced by the breaking of -parity through the vacuum expectation value of the odd Higgs singlet. Examples of left–right symmetric and mirror fermions models in grand unified theories are presented. PACS 12.60.Cn; 14.80.Cp; 12.10.Dm     

中微子振荡及CP破坏理论描述

2015年10月6日,诺贝尔物理学奖授予日本物理学家鶨田隆章和加拿大物理学家阿瑟·麦克唐纳,以表彰他们发现中微子振荡并证实中微子有质量.同年11月8日,包括鶨田隆章和麦克唐纳在内的7名在中微子振荡研究中做出关键贡献的科学家获得2016年度基础物理学突破奖.中微子振荡成为基础物理学研究的焦点.本文从量子力学理论出发,对中微子振荡及CP破坏理论作简要的描述,并介绍未来中微子研究中的若干重大科学问题.     

A gauge model without parity violation in heavy atoms

We address the question: “are weak right-handed non-singlet representations of quarks and leptons necessary?” An extension of the Weinberg-Salam model to SU(2) ? U(1) ? U(1) is found to adequately describe all existing weak interaction data including the lack of parity violation in atomic physics experiments. These data tightly constrain the additional parameters introduced by adding the second weak hypercharge. Although such a model may seem regressive when considered from the standpoint of “simple” unification schemes, we feel that it is aesthetics rather than experiment which leads to non-trivial right-handed multiplet structure. In contrast to most other models, ours predicts a substantial parity-violation effect in atomic experiments on hydrogen. We note that the second weak boson in our model is not constrained to be heavy by existing data and thus might already by accessable in pp → μ⁺μ^?X or possibly in the next generation of colliding beam facilities through e⁺e^? → μ⁺μ^?.     

Matter effects in active-sterile solar neutrino oscillations

We study the matter effects for solar neutrino oscillations in a general scheme, without any constraint on the number of sterile neutrinos and the mixing matrix elements, only assuming a realistic hierarchy of neutrino squared-mass differences in which the smallest squared-mass difference is effective in solar neutrino oscillations. The validity of the analytic results is illustrated with a numerical solution of the evolution equation in the simplest case of four-neutrino mixing with the realistic matter density profile inside the Sun.     

Influence of solar flares on neutrino oscillations

The solar neutrino problem is considered within the framework of a model based on the gauge group SU(2)_L×SU(2)_R×U(1)_B−L. An evolutionary equation is found for the eight-component wave function and a scheme for possible resonant transitions is determined with allowance for the Majorana nature of the neutrino. The influence of solar flares on the oscillation pattern of the neutrino flux is investigated. Yankya Kupala State University, Grodno. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 116–120, June, 1996.     

A search for neutrino oscillations

We present here the final results of experiments searching for neutrino oscillations, carried out by the CHARM Collaboration. The data — taking took place in 1983. The first experiment was performed by exposing two detectors simultaneously to the CERN PS low energyv _µ beam. In the second experiment the full CHARM detector was exposed to the wide-band horn-focusedv _µ beam of the CERN SPS. Complete details of the experiments and data reduction are presented. No statistically significant signals for neutrino oscillations were observed. Our 90% CL limits in the appearance experiment (v _µ→v _e ) exclude Δm ²≧0.19 eV² for complete mixing (sin²2θ=1), and sin²2θ≧0.008 for the region Δm ²≧30 eV². These results, and the limits observed for (v _µ→v _x ) (disappearance of (v _µ), are in agreement with those of most other experiments but exclude part of the region previously reported as a possible indication ofv _µ→v _e oscillations.     

Lorentz violation constrained by triplicity of lepton families and neutrino oscillations

In this paper we postulate an algebraic model to relate the triplet characteristic of lepton families to Lorentz violation. Inspired by the two-to-one mapping between the group SL（2, C） and the Lorentz group via the Pauli grading （the elements of SL（2, C） expressed by direct sum of unit matrix and generators of SU（2） group）, we grade the SL（3,C） group with the generators of SU（3）, i. e. the Gell-Mann matrices, then express the SU（3） group in terms of three SU（2） subgroups, each of which stands for a lepton species and is mapped into the proper Lorentz group as in the case of the group SL（2,C）. If the mapping from group SL（3,C） to the Lorentz group is constructed by choosing one SU（2） subgroup as basis, then the other two subgroups display their impact only by one more additional generator to that of the original Lorentz group. Applying the mapping result to the Dirac equation, it is found that only when the kinetic vertex -γμθ^μ is extended to encompass γ5γμθ^μ can the Dirac-equation-form be conserved. The generalized vertex is useful in producing neutrino oscillations and mass differences.     

Lorentz violation constrained by triplicity of lepton families and neutrino oscillations

In this paper we postulate an algebraic model to relate the triplet characteristic of lepton families to Lorentz violation. Inspired by the two-to-one mapping between the group SL(2, C) and the Lorentz group via the Pauli grading (the elements of SL(2, C) expressed by direct sum of unit matrix and generators of SU (2) group), we grade the SL(3, C) group with the generators of SU(3), i. e. the Gell-Mann matrices, then express the SU(3) group in terms of three SU(2) subgroups, each of which stands for a lepton species and is mapped into the proper Lorentz group as in the case of the group SL(2,C). If the mapping from group SL(3,C) to the Lorentz group is constructed by choosing one SU(2) subgroup as basis, then the other two subgroups display their impact only by one more additional generator to that of the original Lorentz group. Applying the mapping result to the Dirac equation, it is found that only when the kinetic vertex γμξμ is extended to encompass γμξμ can the Dirac-equation-form be conserved. The generalized vertex is useful in producing neutrino oscillations and mass differences.