Linear seesaw model with T7 symmetry for neutrino mass and mixing

We propose a low-scale Standard Model extension with T_(7)×Z_(4)×Z_(3)×Z_(2) symmetry that can successfully explain observed neutrino oscillation results within the 3σrange.Small neutrino masses are obtained via the linear seesaw mechanism.Normal and inverted neutrino mass orderings are considered with three lepton mixing angles in their experimentally allowed 3σranges.The model provides a suitable correlation between the solar and reactor neutrino mixing angles,which is consistent with the TM2 pattern.The prediction for the Dirac phase isδCP∈(295.80,330.0)°for both normal and inverted orderings,including its experimentally maximum value,while those for the two Majorana phases areη1∈(349.60,356.60)°,η2=0 for normal ordering andη1∈(3.44,10.37)°,η2=0 for inverted ordering.In addition,the predictions for the effective neutrino masses are consistent with the pre sent experimental bounds.

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 （e, 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 tind 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 CK.M 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 10^12- 10^15 GeV. We also discuss RG effects on V^13.

Determining the Neutrino Mass Eigenstates and the Effective Majorana Mass

This paper aims at solving several open questions in current neutrino physics: the neutrino mass hierarchy, the Dirac CP violating phase, the absolute mass of neutrinos, the nature of neutrinos (Dirac or Majorana), the Majorana matrix and the absolute value of the effective Majorana neutrino mass. In the research presented in this paper, we have shown that the precise definition of the mass splittings between neutrino mass eigenstates, done in the latest analysis of experimental data, can be of crucial importance for defining the nature of neutrino mass hierarchy. The Standard Model has three generations of fundamental matter particles. Three generations of the charged lepton mass show a hierarchical structure: mτ > mμ > me. Owing to that, there is a belief and it is considered that neutrinos may follow such hierarchical structure. In our calculations, we have also included the latest data obtained, based on the processing of measurement results, which showed that even with such data, obtained results favor the normal neutrino mass hierarchy. As for the individual neutrino mass calculated in this paper, in today’s neutrino physics it is only known that neutrino mass scale is bounded only from above, and both the Dirac and the Majorana character of neutrinos are compatible with all observations. Among some of the questions resolved in this paper, which are related to the properties of neutrinos, a positive answer was also given to the question of whether light neutrinos are self-conjugate particles or not.

B-L model with D_(4)×Z_(4)×Z_(2)symmetry for fermion mass hierarchies and mixings

We constructed a gauge B-L model with D_(4)×Z_(4)×Z_(2)symmetry to explain the quark and lepton mass hierarchies and their mixings with realistic CP phases via the type-I seesaw mechanism.Six quark mases,three quark mixing angles,and the CP phase in the quark sector take the central values whereas Yukawa couplings in the quark sector are diluted in a range of difference of three orders of magnitude by the perturbation theory at the first order.Concerning the neutrino sector,a small neutrino mass is achieved by the type-I seesaw mechanism.Both inverted and normal neutrino mass hierarchies are consistent with the experimental data.The predicted sum of neutrino masses for normal and inverted hierarchies,the effective neutrino masses,and the Dirac CP phase are also consistent with recently reported limits.

Multiscalar B-L extension based on S_(4)flavor symmetry for neutrino masses and mixing

A multiscalar and nonrenormalizable B-L extension of the standard model(SM)with S_(4)symmetry which successfully explains the recently observed neutrino oscillation data is proposed.The tiny neutrino masses and their hierarchies are generated via the type-I seesaw mechanism.The model reproduces the recent experiments of neutrino mixing angles and Dirac CP violating phase in which the atmospheric angle(θ_(23))and the reactor angle(θ_(13))get the best-fit values while the solar angle(θ_(12))and Dirac CP violating phase(δ)are in 3σrange of the best-fit value for the normal hierarchy(NH).For the inverted hierarchy(IH),θ13 gets the best-ft value andθ_(23)together withδare in the lσrange,whileθ12 is in 3δrange of the best-fit value.The effective neutrino masses are pre-dicted to be(m_(ee))=6.81 meV for the NH and(m_(ee))=48.48 meV for the IH,in good agreement with the most re-cent experimental data.

Neutrino masses,cosmological inflation and dark matter in a variant U(1)B-L model with type II seesaw mechanism

In this study,we implemented the type Ⅱ seesaw mechanism into the framework of the U(l)B-L gauge model.To achieve this,we added a scalar triplet,A,to the canonical particle content of the U(l)B-Lgauge model.By imposing that the U(l)B-L gauge symmetry be spontaneously broken at TeV scale,we show that the type Ⅱ seesaw mechanism is realized at an intermediate energy scale,more precisely,at approximately 109 GeV.To prevent heavy right-handed neutrinos from disturbing the mechanism,we evoke a Z2 discrete symmetry.Interestingly,as a result,we have standard neutrinos with mass around eV scale and right-handed neutrinos with mass in TeV scale,with the lightest one fulfilling the condition of dark matter.We developed all of these in this study.In addition,we show that the neutral component of Δ may perform unproblematic non-minimal inflation with loss of unitarity.

A non-renormalizable B-L model with Q_(4)×Z_(4)×Z_(2) flavor symmetry for cobimaximal neutrino mixing

We construct a non-renormalizable gauge B-L model based on Q_(4)×Z_(4)×Z_(2) symmetry that successfully explains the cobimaximal lepton mixing scheme.Small active neutrino masses and both neutrino mass hierarchies are produced via the type-I seesaw mechanism at the tree-level.The model is predictive;hence,it reproduces the cobimaximal lepton mixing scheme,and the reactor neutrino mixing angle θ_(13) and the solar neutrino mixing angle θ_(12) can obtain best-fit values from recent experimental data.Our model also predicts the effective neut-rino mass parameters of mβ∈(8.80,9.05)meV and〈m_(ee)〉∈(3.65,3.95)meV for normal ordering(NO)and mβ ∈(49.16,49.2 l)meV and(mce)∈(48.59,48.67)meV for inverted ordering(IO),which are highly consistent with recent experimental constraints.

Earthquake forecast via neutrino tomography

We discuss the possibility of forecasting earthquakes by means of （anti）neutrino tomography. Antineutrinos emitted from reactors are used as a probe. As the antineutrinos traverse through a region prone to earthquakes, observable variations in the matter effect on the antineutrino oscillation would provide a tomography of the vicinity of the region. In this preliminary work, we adopt a simplified model for the geometrical profile and matter density in a fault zone. We calculate the survival probability of electron antineutrinos for cases without and with an anomalous accumulation of electrons which can be considered as a clear signal of the coming earthquake, at the geological region with a fault zone, and find that the variation may reach as much as 3% for νˉe emitted from a reactor. The case for a νe beam from a neutrino factory is also investigated, and it is noted that, because of the typically high energy associated with such neutrinos, the oscillation length is too large and the resultant variation is not practically observable. Our conclusion is that with the present reactor facilities and detection techniques, it is still a difficult task to make an earthquake forecast using such a scheme, though it seems to be possible from a theoretical point of view while ignoring some uncertainties. However, with the development of the geology, especially the knowledge about the fault zone, and with the improvement of the detection techniques, etc., there is hope that a medium-term earthquake forecast would be feasible.

Testing lepton f lavor universality in terms of BESⅢ and charm-tau factory data

The recent measurements on Rκ and Rπ imply that there exists a possible violation of the leptonic flavor universality which is one of the cornerstones of the Standard Model. It is suggested that a mixing between sterile and active neutrinos might induce such a violation. In this work we consider the scenarios with one or two sterile neutrinos to explicitly realize the data while the constraints from the available experiments have been taken into account. Moreover, as indicated in literature, the deviation of the real PMNS matrix from the symmetric patterns may be due to a μ-τ asymmetry, therefore the measurements on RD（Ds）eμ=F（D（Ds）→e＋νe）/Г（D（Ds）→μ＋νμ） and RD（Ds）μτ=Г（D（Ds）→μ＋νμ）Г（D（Ds）→ι＋ντ） （and for some other heavy mesons B± and Bc etc.） may shed more light on the physics responsible for the violation of the leptonic flavor universality. The data of BESⅢ are available to test the universality and that of future charm-tau factories will provide more accurate information. In this work, we will discuss RD（Ds）eμ and RD（Ds）μτ in detail and also briefly consider the cases for B± and Bc.

Optimization of Neutrino Oscillation Parameters Using Differential Evolution

We show how the traditional grid based method for finding neutrino oscillation parameters △m2 and tan2θ can be combined with an optimization technique, Differential Evolution （DE）, to get a significant decrease in computer processing time required to obtain minimal chi-square （χ2） in four different regions of the parameter space. We demonstrate efficiency for the two-neutrinos case. For this, the χ2 function for neutrino oscillations is evaluated for grids with different density of points in standard allowed regions of the parameter space of △m2 and tan2θ using experimental and theoretical total event rates of ehlorine （Homestake）, Gallex＋GNO, SAGE, Superkamiokande, and SNO detectors. We find that using DE in combination with the grid based method with smail density of points can produce the results comparable with the one obtained using high density grid, in much lesser computation time.