Parameterization for Neutrino Mixing Matrix with Deviated Unitarity

Neutrino oscillation experiments provide the first evidence on non-zero neutrino masses and indicate new physics beyond the standard model. With Majorana neutrinos introduced to acquire tiny neutrino masses, it leads to the existence of more than three neutrino species, implying that the ordinary neutrino mixing matrix is only a part of the whole extended unitary mixing matrix and thus no longer unitary. We give a parameterization for a non-unitary neutrino mixing matrix under seesaw framework and further present a method to test the unitarity of the ordinary neutrino mixing matrix.     

Systematic impact of spent nuclear fuel on θ13 sensitivity at reactor neutrino experiment

Reactor neutrino oscillation experiments, such as Daya Bay, Double Chooz and RENO are designed to determine the neutrino mixing angle θ13 with a sensitivity of 0.01--0.03 in sin^2 2θ13 at 90% confidence level, an improvement over the current limit by more than one order of magnitude. The control of systematic uncertainties is critical to achieving the sin^22θ13 sensitivity goal of these experiments. Antineutrinos emitted from spent nuclear fuel （SNF） would distort the soft part of energy spectrum and may introduce a non-negligible systematic uncertainty. In this article, a detailed calculation of SNF neutrinos is performed taking account of the operation＂ of a typical reactor and the event rate in the detector is obtained. A further estimation shows that the event rate contribution of SNF neutrinos is less than 0.2% relative to the reactor neutrino signals. A global X2 analysis shows that this uncertainty will degrade the θ13 sensitivity at a negligible level.     

Neutrino Lensing

Due to the intrinsic properties of neutrinos, the gravitational lens effect for a neutrino should be more colorful and meaningful than the normal lens effect of a photon. Other than the experiments operated at terrestrial laboratory, in principle, we can propose a completely new astrophysical method to determine not only the nature of the gravity of lens objects but also the mixing parameters of neutrinos by analyzing neutrino trajectories near the central objects. However, the angular, energy and time resolution of the neutrino telescopes are still comparatively poor, so we just concentrate on the two classical tests of general relativity, i.e. the angular deflection and the time delay of the neutrino by a lens object as a preparative work in this paper. In addition, some simple properties of neutrino lensing are investigated.     

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）.     

A New Type of Accessible Environmental Influences on Neutrino Oscillation

Considering a new type of environment influences,we use a two-energy-level(ν1-ν2) quantum system to investigate neutrino oscillations in medium.Besides the matter effects derived by Wolfenstein,there may exist extra terms due to a unitary evolution of the system between pure and mixed states,so the evolution equation is modified obviously.We show that the extra terms may play some role and induce observable effects in solar neutrino problem,especially,in the long baseline neutrino oscillation experiments which are under serious consideration recently,if the parameters fall into a suitable region.     

Neutrino mixing matrix and masses from a particular two-zero texture based on A4 symmetry

The current study aims to investigate the particular case of two zeros in a Majorana neutrino mass matrix based on A₄ symmetry,where charged lepton mass matrix is diagonal.The texture is ■ with(μ,μ) and(τ,τ) vanishing element of the neutrino mass matrix.The texture ■ has magic and μ-τ symmetry,with a tribimaximal form of the mixing matrix,which leads to θ₁₃=0 that it is not consistent with experimental data and at first,does not seem to be allowed.Since θ₁₃ a sma...     

Implications of fermionic dark matter on recent neutrino oscillation data

We investigate flavor phenomenology and dark matter in the context of the scotogenic model.In this model,the neutrino masses are generated through radiative corrections at the one-loop level.Considering the neutrino mixing matrix to be of tri-bimaximal form with additional perturbations to accommodate the recently observed nonzero value of the reactor mixing angle θ_(13),we obtain the relation between various neutrino oscillation parameters and the model parameters.Working in a degenerate heavy neutrino mass spectrum,we obtain light neutrino masses obeying the normal hierarchy and also study the relic abundance of fermionic dark matter candidates,including coannihilation effects.A viable parameter space is thus obtained,consistent with neutrino oscillation data,relic abundance and various lepton flavor violating decays such as 1_α→1_(βγ) and 1_α→31_β.     

Detection of Supernova Neutrinos on the Earth for Large θ_(13)

Supernova （SN） neutrinos detected on the Earth are subject to the shock wave effects, the Mikheyev- Smirnov-Wolfenstein （MSW） effects, the neutrino collective effects and the Earth matter effects. Considering the recent experimental result about the large mixing angle 013 （-8.8°） provided by the Daya Bay Collaboration and applying the available knowledge for the neutrino conversion probability in the high resonance region of SN, PH , which is in the form of hypergeometric function in the case of large 813, we deduce the expression of PH taking into account the shock wave effects. It is found that PH is not zero in a certain range of time due to the shock wave effects. After considering all the four physical effects and scanning relevant parameters, we calculate the event numbers of SN neutrinos for the ＂Garehing＂ distribution of neutrino energy spectrum. From the numerical results, it is found that the behaviors of neutrino event numbers detected on the Earth depend on the neutrino mass hierarchy and neutrino spectrum parameters including the dimensionless pinching parameter βa （where a refers to neutrino flavor）, the average energy 〈Ea〉, and the SN neutrino luminosities La. Finally, we give the ranges of SN neutrino event numbers that will be detected at the Daya Bay experiment.     

Distinguishable RGE Running Effects Between Dirac Neutrinos and Majorana Neutrinos with Vanishing Majorana CP-Violating Phases

In a novel parametrization of neutrino mixing and in the approximation of τ-lepton dominance, we show that the one-loop renormalization-group equations （RGEs） of Dirac neutrinos are different from those of Majorana neutrinos even if two Majorana CP-violating phases vanish. As the latter can keep vanishing from the electroweak scale to the typical seesaw scale, it makes sense to distinguish between the RGE running effects of neutrino mixing parameters in Dirac and Majorana cases. The differences are found to be quite large in the minimal supersymmetric standard model with sizable tan β, provided the masses of three neutrinos are nearly degenerate or have an inverted hierarchy.     

Lepton Flavor Violating Z →lIlJ in SO（3） Gauge Extension of SM

The SO（3） gauge extension of SM, which is proposed to present a successful explanation for the observed small masses of neutrino and the nearly tri-bimaximal neutrino mixing, predicted the vector-like SO（3） triplet Majorana neutrinos and SUL（2） double Higgs bosons. In this work we calculate branching ratios of the charged lepton flavor violating decays lIlJV （V = γ, Z） induced by these Majorana neutrinos and Higgs bosons. We find that under the model parameters constrained by experimental bounds on the decays Z →lIlJ, the branching ratio of decays lI→lJγ can be up to 10^-10, which may be accessible at the future experiments.     

Neutrino mass ordering and μ-τ reflection symmetry breaking

If the neutrino mass spectrum turns out to be m_3 m_1 m_2, it may be relabeled as m_1 m_2 m_3 such that all the masses of fundamental fermions with the same electrical charges are in order. In this case the columns of the 3×3 lepton flavor mixing matrix U should be reordered accordingly, and the resulting pattern U may involve one or two large mixing angles in the standard parametrization or its variations. Since the Majorana neutrino mass matrix remains unchanged in such a mass relabeling, a possible μ-τ reflection symmetry is respected in this connection and its breaking effects are model-independently constrained at the 3σ level by using current experimental data.     

Update on two-zero textures of the Majorana neutrino mass matrix in light of recent T2K,Super-Kamiokande and NOνA results

The latest results from atmospheric and accelerator neutrino experiments indicate that the normal neutrino mass ordering m_1 m_2 m_3, a maximal leptonic CP-violating phase δ = 270° and the second octant of neutrino mixing angle θ_23 45° are favored. In light of new experimental results, we update previous phenomenological studies on two-zero textures of the Majorana neutrino mass matrix M-_ν, in the flavor basis where the charged-lepton mass matrix M_l is diagonal. When the 1σ ranges of neutrino mixing parameters are taken into account, only four(i.e., A_(1,2)and B_(2,4)) among seven two-zero patterns of Mνshow the aforementioned features of neutrino mass spectrum, mixing angle θ_23and CP-violating phase δ, and thus are compatible with the latest neutrino oscillation data. The correlative relations among neutrino masses and mixing parameters have been derived analytically for these four patterns, and the allowed regions of neutrino mixing angles and the CP-violating phase are also given. Possible realizations of four viable two-zero textures via non-Abelian discrete flavor symmetries are discussed.     

An Underlying Symmetry Determines all Elements of CKM and PMNS up to a Universal Constant?

Observing the CKM matrix elements written in different parametrization schemes,one can notice obvious relations among the sine-values of the CP phases in those schemes.Using the relations,we establish a few parametrizationindependent equations,by which the matrix elements of the CKM matrix can be completely fixed up to a universal parameter.If it is true,we expect that there should exist a hidden symmetry in the nature,which determines the relations.Moreover,it requires a universal parameter,naturally it would be the famous Jarlskog invariant,which is also parametrization independent.Thus the four parameters(three mixing angles and one CP phase) of the CKM matrix are not free,but determined by the symmetry and the universal parameter.As we generalize the rules to the PMNS matrix for neutrino mixing,the CP phase of the lepton sector is predicted to be within a range of 0 ~ 59° centered at39°(in the P_a parametrization) which will be tested in the future experiments.     

太阳中微子问题研究进展

系统评述了国际上对太阳中微子研究的进展 ,说明了核物理实验对研究太阳中微子问题作出的贡献 ,对未来的中微子实验作了展望.The comparison between experimental results and theoretical predictions has yielded the solar neutrino problem. Over the years, the large communities of astrophysics and of nuclear physics took enormous efforts in solving this problem. The current progress on the study of solar neutrino problem is reviewed. Nuclear physics can make a significant contribution to this problem. The importance of the nuclear physics experiment is introduced. To minimize the uncertainties of neutrino detection has led to new...     

Solar Neutrino Oscillation Parameters after SNO Phase-Ⅲ and SAGE Part-Ⅲ

We analyse the recently published results from solar neutrino experiments SNO Phase-Ⅲ and SAGE Part-Ⅲ and show their constraints on solar neutrino oscillation parameters, especially for the mixing angle θ12. Through a global analysis using all existing data from SK, SNO, Ga＆Cl radiochemieal experiments and long base fine reactor experiment KamLAND, we obtain the parameters △m12^2= 7.684 -0.208^＋0.212×10^-5 eV^2, tan^2 θ12=0.440-0.057^＋0.059. also find that the discrepancy between the KamLAND and solar neutrino results can be reduced by choosing a small non-zero value for the mixing angle θ13.     

Naumov- and Toshev-like relations in the renormalization-group evolution of quarks and Dirac neutrinos

In an analytical way of studying matter effects on neutrino oscillations, the Naumov and Toshev relations have been derived to respectively link the Jarlskog invariant of CP violation and the Dirac phase in the standard parametrization of the 3×3 flavor mixing matrix to their matter-corrected counterparts. Here we show that there exist similar relations for Dirac neutrinos and charged leptons evolving with energy scales via the one-loop renormalizationgroup(RG) equations in the tau-dominance approximation, and for the running behaviors of up-and down-type quarks in the top-dominance approximation, provided a different parametrization is taken into account.     

Dirac Neutrino Masses in NCG

Several models in nonocmmutative geometry(NCG) with mild changes to the standard model are introduced to discuss the neutrino mass problem.we use two constraints,Poincare duality and gauge anomaly free,to discuss the possibility of containing right-handed neutrinos in them.Our work shows that no model in this paper,with each generation containing a right-handed neutrino,can satisfy these two constraints at the same time.So,to consist with neutrino oscillation experiment results,maybe fundamental changes to the present version of NCG are usually needed to include Dirac massive neutrinos.     

利用大亚湾中微子实验装置探测超新星中微子

在利用大亚湾中微子实验装置研究超新星中微子探测过程中, 需要考虑到中微子传播过程中受到各种效应的影响, 包括超新星震荡效应、中微子集体效应、 Mikheyev Smirnov Wolfenstein (MSW)效应和地球物质效应等。 由于超新星中微子受到这些效应, 不同味道的中微子之间振荡会发生变化, 因而利用探测某些超新星中微子事例数之比, 就有可能确定中微子的质量层次,得到中微子混合角θ13和中微子绝对质量的信息。 While detecting supernova neutrinos in the Daya Bay neutrino laboratory, several supernova neutrino effects need to be considered, including the supernova shock effects, the neutrino collective effects, the Mikheyev Smirnov Wolfenstein (MSW) effects, and the Earth matter effects. The phenomena of neutrino oscillation is affected by the above effects. Using some ratios of the event numbers of different supernova neutrinos, we propose some possible methods to identify the mass hierarchy and acquire information about the neutrino mixing angle θ13 and neutrino masses.