共查询到20条相似文献,搜索用时 265 毫秒
1.
We analyse the structure of the neutrino mass matrix and the pattern of neutrino oscillations in the O(10) model with radiatively induced Majorana masses. In particular, we show that the possibility of experimentally interesting neutrino oscillations is left open. 相似文献
2.
The origin of the hot phase of the early universe remains so far an unsolved puzzle. A viable option is entropy production through the decays of heavy Majorana neutrinos whose lifetimes determine the initial temperature. We show that baryogenesis and the production of dark matter are natural by-products of this mechanism. As is well known, the cosmological baryon asymmetry can be accounted for by leptogenesis for characteristic neutrino mass parameters. We find that thermal gravitino production then automatically yields the observed amount of dark matter, for the gravitino as the lightest superparticle and typical gluino masses. As an example, we consider the production of heavy Majorana neutrinos in the course of tachyonic preheating associated with spontaneous B−L breaking. A quantitative analysis leads to constraints on the superparticle masses in terms of neutrino masses: For a light neutrino mass of 10−5 eV the gravitino mass can be as small as 200 MeV, whereas a lower neutrino mass bound of 0.01 eV implies a lower bound of 9 GeV on the gravitino mass. The measurement of a light neutrino mass of 0.1 eV would rule out heavy neutrino decays as the origin of entropy, visible and dark matter. 相似文献
3.
T. Fukuyama T. Kikuchi K. Matsuda 《The European Physical Journal C - Particles and Fields》2008,55(4):623-628
Constraints on the heavy sterile neutrino mixing angles are studied in the framework of a minimal supersymmetric SO(10) model
with the use of the double see-saw mechanism. A new singlet matter in addition to the right-handed neutrinos is introduced
to realize the double see-saw mechanism. The light Majorana neutrino mass matrix is, in general, given by a combination of
those of the singlet neutrinos and the active neutrinos. The minimal SO(10) model is used to give an example form of the Dirac
neutrino mass matrix, which enables us to predict the masses and the mixing angles in the enlarged 9×9 neutrino mass matrix.
Mixing angles between the light Majorana neutrinos and the heavy sterile neutrinos are shown to be within the LEP experimental
bound on all ranges of the Majorana phases. 相似文献
4.
We propose the inverse seesaw mechanism as a way to understand small Majorana masses for neutrinos in warped extra dimension models with seesaw scale in the TeV range. The ultra-small lepton number violation needed in implementing inverse seesaw mechanism in 4D models is explained in this model as a consequence of lepton number breaking occurring on the Planck brane. We construct realistic models based on this idea that fit observed neutrino oscillation data for both normal and inverted mass patterns. We compute the corrections to light neutrino masses from the Kaluza-Klein modes and show that they are small in the parameter range of interest. Another feature of the model is that the absence of global parity anomaly implies the existence of at least one light sterile neutrino with sterile and active neutrino mixing in the range suggested by the LSND and MiniBooNE observations. 相似文献
5.
We present the generic formulas to calculate the ratios of neutrino masses and the Majorana phases of CP violation from the neutrino mass matrix with two independent vanishing entries in the flavor basis where the charged lepton mass matrix is diagonal. An order-of-magnitude illustration is given for seven experimentally acceptable textures of the neutrino mass matrix, and some analytical approximations are made for their phenomenological consequences at low energy scales. 相似文献
6.
N. Nimai Singh H. Zeen Devi Amal Kr Sarma Mahadev Patgiri 《Indian Journal of Physics》2010,84(6):751-755
We consider the Majorana CP violating phases derived from right-handed Majorana mass matrices to estimate the baryon asymmetry
of the universe, for different neutrino mass models, namely degenerate, inverted hierarchical and normal hierarchical models,
with tri-bimaximal mixings. Considering three possible diagonal forms of Dirac neutrino mass matrix as charged-lepton, up-quark
or down-quark mass matrix within the framework of left-right symmetric GUT models, the right-handed Majorana mass matrices
are constructed from the light Majorana neutrino mass matrix through the inverse seesaw formula. These light neutrino mass
matrices have already been tested to provide good predictions on neutrino mass parameters and mixing angles. They are again
applied to predict baryon asymmetry of the universe in the present work. The normal hierarchical model gives the best prediction
for baryon asymmetry, consistent with observation. The analysis may serve as additional information in the discrimination
of the presently available neutrino mass models. 相似文献
7.
A. Ali A.V. Borisov N.B. Zamorin 《The European Physical Journal C - Particles and Fields》2001,21(1):123-132
We discuss same-sign dilepton production mediated by Majorana neutrinos in high-energy proton–proton collisions for at the LHC energy TeV, and in the rare decays of the , and B mesons of the type . For the pp reaction, assuming one heavy Majorana neutrino of mass , we present discovery limits in the plane where are the mixing parameters. Taking into account the present limits from low-energy experiments, we show that at LHC one has
sensitivity to heavy Majorana neutrinos up to a mass TeV in the dilepton channels , and , but the dilepton states will not be detectable due to the already existing constraints from neutrinoless double beta decay. We work out a large number
of rare meson decays, both for the light and heavy Majorana neutrino scenarios, and argue that the present experimental bounds
on the branching ratios are too weak to set reasonable limits on the effective Majorana masses.
Received: 24 April 2001 / Published online: 29 June 2001 相似文献
8.
The seesaw mechanism provides a simple explanation for the lightness of the known neutrinos. Under the standard assumption of a weak scale Dirac mass and a heavy sterile Majorana scale the neutrino mass is naturally suppressed below the weak scale. However, Nature may employ Dirac and Majorana scales that are much less than typically assumed, possibly even far below the weak scale. In this case the seesaw mechanism alone would not completely explain the lightness of the neutrinos. In this work we consider a warped framework that realizes this possibility by combining naturally suppressed Dirac and Majorana scales together in a mini-seesaw mechanism to generate light neutrino masses. Via the AdS/CFT correspondence the model is dual to a 4D theory with a hidden strongly coupled sector containing light composite right-handed neutrinos. 相似文献
9.
Sneutrino-antisneutrino mixing and neutrino mass in anomaly-mediated supersymmetry breaking scenario
In supersymmetric models with nonzero Majorana neutrino mass, the sneutrino and antisneutrino mix, which may lead to same-sign dilepton signals in future collider experiments. We point out that the anomaly-mediated supersymmetry breaking scenario has a good potential to provide an observable rate of such signals for the neutrino masses suggested by the atmospheric and solar neutrino oscillations. It is noted also that the sneutrino-antisneutrino mixing can provide much stronger information on some combinations of the neutrino masses and mixing angles than the neutrino experiments. 相似文献
10.
E. Papageorgiu 《Zeitschrift fur Physik C Particles and Fields》1995,65(1):135-150
Starting from a complete set of possible parametrisations of the quark-mass matrices that have the maximum number of texture zeros at the grand unification scale, and the Georgi-Jarlskog mass relations, we classify the neutrino spectra with respect to the unknown structure of the heavy Majorana sector. The results can be casted into a small number of phenomenologically distinct classes of neutrino spectra, characterised by universal mass-hierarchy and oscillation patterns. One finds that the neutrino masses reflect the natural hierarchy among the three generations and obey the quadratic seesaw, for most GUT models that contain a rather “unsophisticated” Majorana sector. A scenario withv τ as the missing hot dark matter component andv e ?v µ oscillations accounting for the solar neutrino deficit comes naturally out of this type of models and is very close to the experimental limit of confirmation or exclusion. In contrast, in the presence of a strong hierarchy of heavy scales or/and some extra symmetries in the Majorana mass matrix, this natural hierarchy gets distorted or even reversed. This fact can become a link between searches for neutrino oscillations and searches for discrete symmetries close to the Planck scale. 相似文献
11.
J. Ellis G.K. Leontaris S. Lola D.V. Nanopoulos 《The European Physical Journal C - Particles and Fields》1999,9(3):389-408
Motivated by the Super-Kamiokande atmospheric neutrino data, we discuss possible textures for Majorana and Dirac neutrino
masses within the see-saw framework. There are two main purposes of this paper: first, to gain intuition into this area from
a purely phenomenological analysis, and second, to explore to what extent it may be realized in a specific model. We comment
initially on the simplified two-generation case, emphasizing that large mixing is not incompatible with a large hierarchy
of mass eigenvalues. We also emphasize that renormalization-group effects may amplify neutrino mixing, and we present semi-analytic
expressions for estimating this amplification. Several examples are then given of three-family neutrino mass textures, which
may also accommodate the persistent solar neutrino deficit, with different assumptions for the neutrino Dirac mass matrices.
We comment on a few features of neutrino mass textures arising in models with a U(1) flavour symmetry. Finally, we discuss the possible pattern of neutrino masses in a “realistic” flipped SU(5) model derived from string theory, illustrating how a desirable pattern of mixing may emerge. Both small- or large-angle
MSW solutions are possible, while a hierarchy of neutrino masses appears more natural than near-degeneracy. This model contains
some unanticipated features that may be relevant in other models also: The neutrino Dirac matrices may not be related closely
to the quark mass matrices, and the heavy Majorana states may include extra gauge-singlet fields.
Received: 6 November 1998 / Published online: 18 June 1999 相似文献
12.
13.
Extending the minimal supersymmetric standard model to explain small neutrino masses via the inverse seesaw mechanism can lead to a new light supersymmetric scalar partner which can play the role of inelastic dark matter (IDM). It is a linear combination of the superpartners of the neutral fermions in the theory (the light left-handed neutrino and two heavy standard model singlet neutrinos) which can be very light with mass in ~5-20 GeV range, as suggested by some current direct detection experiments. The IDM in this class of models has keV-scale mass splitting, which is intimately connected to the small Majorana masses of neutrinos. We predict the differential scattering rate and annual modulation of the IDM signal which can be testable at future germanium- and xenon-based detectors. 相似文献
14.
N. Haba Y. Matsui N. Okamura 《The European Physical Journal C - Particles and Fields》2000,17(3):513-520
Neutrino-oscillation solutions for the atmospheric neutrino anomaly and the solar neutrino deficit can determine the texture
of the neutrino mass matrix according to three types of neutrino mass hierarchy: Type A: , Type B: , and Type C: , where is the absolute mass of the ith generation neutrino. The relative sign assignments of the neutrino masses in each type of mass hierarchy play crucial roles
in the stability against quantum corrections. Actually, two physical Majorana phases in the lepton flavor mixing matrix connect
the relative sign assignments of the neutrino masses. Therefore, in this paper we analyze the stability of the mixing angles
against quantum corrections according to three types of neutrino mass hierarchy (Type A, B, C) and two Majorana phases. The
two phases play crucial roles in the stability of the mixing angles against quantum corrections.
Received: 9 May 2000 / Revised version: 23 May 2000 / Published online: 8 September 2000 相似文献
15.
The lepton asymmetry generated by the out-of-equilibrium decays of heavy Majorana neutrinos with a quasi-degenerate mass spectrum is resonantly enhanced. In this work, we study this scenario within a first-principle approach. The quantum field theoretical treatment is applicable for mass splittings of the order of the width of the Majorana neutrinos, for which the enhancement is maximally large. The non-equilibrium evolution of the mixing Majorana neutrino fields is described by a formal analytical solution of the Kadanoff–Baym equations, that is obtained by neglecting the back-reaction. Based on this solution, we derive approximate analytical expressions for the generated asymmetry and compare them to the Boltzmann result. We find that the resonant enhancement obtained from the Kadanoff–Baym approach is smaller compared to the Boltzmann approach, due to additional contributions that describe coherent transitions between the Majorana neutrino species. We also discuss corrections to the masses and widths of the degenerate pair of Majorana neutrinos that are relevant for very small mass splitting, and compare the approximate analytical result for the lepton asymmetry with numerical results. 相似文献
16.
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. 相似文献
17.
The presence of domain walls separating regions of unbrokenSU(2)L andSU(2)R is shown to provide necessary conditions for leptogenesis which converts later to the observed baryon asymmetry. The strength
of lepton number violation is related to the Majorana neutrino mass and hence related to current bounds on light neutrino
masses. Thus the observed neutrino masses and the baryon asymmetry can be used to constrain the scale of left-right symmetry
breaking. 相似文献
18.
A "new" scenario is proposed for baryogenesis. We show that the delayed decay of colored Higgs particles in grand unified theories may generate an excess baryon number of the empirically desired amount, if the mass of the heaviest neutrino is in the range 0.02 eV相似文献
19.
《Nuclear Physics B》1995,436(3):461-473
A very simple extension of the Standard Model to include an Abelian family symmetry is able to describe the hierarchy of quark and lepton masses and their mixing angles together with the unification of gauge couplings. We consider the implications of this model for neutrino masses and mixing angles and show that they are determined up to a discrete ambiguity corresponding to the representation content of the Higgs sector responsible for the Majorana mass matrix. 相似文献
20.
Eligio Lisi 《Progress in Particle and Nuclear Physics》2010,64(2):171-177
Established results on neutrino mass, mixing and flavor change (as of 2009) are briefly reviewed. Status and prospects of unknown neutrino properties (smallest mixing angle, Dirac/Majorana nature, absolute masses and their hierarchy) are also discussed. 相似文献