Neutrino masses and mixings using updated values of running quark and lepton masses (original) (raw)
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An SO(10) model with adjoint fermions for double seesaw neutrino masses
2010
An SO(10)SO(10)SO(10) model where the 10H10_H10H and 120H120_H120H representations are used for generating fermion masses is quite predictive, though due to the absence of SU(2)L,RSU(2)_{L,R}SU(2)L,R triplet/singlet fields it cannot give rise to neutrino masses through the usual type-I or type-II seesaw mechanisms. In this paper for neutrino masses we propose an extension of such an SO(10)SO(10)SO(10) model by adding fermions in the adjoint representation (${45}_F$) and a symmetry breaking scalar bar16H\bar{16}_Hbar16H. The bar16H\bar{16}_Hbar16H couples the adjoint fermions to the standard fermions in 16F{16}_F16F and induces neutrino masses through the `double seesaw' mechanism. In order to enhance the predictivity of the model we impose mu−tau\mu-\taumu−tau flavour symmetry on the Yukawa matrices for 10H10_H10H and bar16H\bar{16}_Hbar16H whereas for the 120H120_H120H it is assumed to be antisymmetric. We discuss the conditions that the mass matrices must obey so that the model can reproduce the tri-bimaximal mixing pattern.
Neutrino Masses and Deviation from Tri-bimaximal mixing in ∆(27) model with Inverse Seesaw Mechanism
We propose a scheme, based on ∆(27) flavor symmetry and supplemented by other discrete symmetries and inverse seesaw mechanism, where both the light neutrino masses and the deviation from tri-bimaximal mixing matrix can be linked to the source of lepton number violation. The hierarchies of the charged leptons are explained. We find that the quark masses including their hierarchies and the mixing can also be constructed in a similar way. The convincing evidence of small but non-vanishing neutrino masses calls for an explanation from a naturalness point of view. It actually points to the existence of new physics beyond the electroweak scale (v). There exist several scenarios to explain this smallness of neutrino masses. Among them, perhaps the most well-studied one is the conventional type-I seesaw mechanism [1]. In this mechanism, the smallness of neutrino mass (m ν) can be obtained in an economic way at the expense of introducing heavy right handed (RH) neutrinos (ν R). For values of Yukawa couplings involved (Y ν) of order unity, the mass scale of ν R (M R) turns out to be near the grand unified scale or so through the relation m ν = −m D M R −1 m T D , where m D = Y ν v. Although interesting , such a large scale is beyond the experimental reach. In this regard, the inverse seesaw mechanism [2-4] offers an interesting resolution through a double suppression by the new physics scale M through m ν = m D M −1 µM T −1 m T D. With a small mass scale µ (of order KeV to few hundred MeV), a relatively low new physics scale (accessible to LHC) associated with M results. However the main caveat of this scenario is to understand the smallness associated with µ or in other words, how it is generated. Note that in case of type-I seesaw, the lepton number violation (LNV) happens through the majorana mass term of the RH neutrinos, which is quite large. Contrary to this, in case of inverse-seesaw, it happens via the µ term which is a tiny scale while compared to the electroweak scale. As the lepton number is only an approximate symmetry of nature, it would be more natural to break it by a small amount rather than by a mass term like M R , which is very large. It can also be argued from the sense of 't Hooft [5], just because in the limit µ tends to zero, the m ν goes to zero and LNV vanishes so that the symmetry is enhanced. In this letter, we explain the desired smallness of µ-term in a flavor symmetric framework. We consider the presence of a ∆(27) flavor symmetry which is supplemented by additional Z 4 ×Z 3 discrete groups. The structure guarantees the non-appearance of the µ-term in the tree level Lagrangian. In fact, it allows the µ-term to be generated only through a significantly higher dimensional operator and thereby suppressing the corresponding interaction by some nonzero powers of the cutoff scale (Λ) of the theory. There are flavon fields, whose vacuum expectation values (vev) would break the flavor symmetry and thereby generates a specific structure of µ and other mass matrices like neutrino Dirac mass matrix (m D), charged leptons etc. We will elaborate more on this as we proceed. In addition, we assume a 2-3 flavor symmetry as an additional symmetry of the La-grangian (particularly for the lepton sector). The only place where this 2-3 symmetry will be broken is in the vev alignment of a single flavon field (σ) responsible for generating the µ term. The vev of all other flavons respect the 2-3 symmetry. So, in a way our framework suggests a unified source (through µ term only) of breaking the 2-3 symmetry and lepton number violation. It is known [6] that a breaking of 2-3 symmetry may indicate a deviation from tri-bimaximal mixing in the neutrino sector. Therefore in this work, we argue that the specific structure obtained for µ not only can explain the small masses of light neutrinos, but also accounts for the deviation from an exact tri-bimaximal mixing by having a nonzero θ 13 at the same time. In realizing the above goal, the fermion field content of the Standard Model (SM) is extended by adding three right handed neutrinos ν Ri (for i = 1, 2, 3), three SM gauge singlet fermions S i which have lepton number opposite to that of the ν Ri. In addition, the scalar sector is extended by adding a set of flavons that break the flavor symmetry around few TeV scale or more. In [6], it was emphasized that both quark and lepton masses and
Physical Review D, 2012
We discuss a 331 model with three scalar triplets and neutral fermion singlets. We show that in the 331 model with right-handed neutrinos, it is possible to obtain small active neutrino masses via the double and inverse seesaw mechanisms, without the use of scalar sextets or triplets with doubly-charged Higgs. Two types of models are discussed. If we have a large Majorana mass matrix for the singlets, the spectrum of neutrinos presents light, heavy and very heavy masses. The other possibility is a small (zero) Majorana mass matrix, which leads to pseudo-Dirac (Dirac) heavy neutrinos in the TeV scale, in addition to the active light neutrinos.
Neutrino masses and deviation from tribimaximal mixing in Δð27Þ model with inverse seesaw mechanism
We propose a scheme, based on Δð27Þ flavor symmetry and supplemented by other discrete symmetries and the inverse seesaw mechanism, where both the light neutrino masses and the deviation from tribimaximal mixing matrix can be linked to the source of lepton number violation. The hierarchies of the charged leptons are explained. We find that the quark masses including their hierarchies and the mixing can also be constructed in a similar way. The convincing evidence of small but nonvanishing neutrino masses calls for an explanation from a naturalness point of view. It actually points to the existence of new physics beyond the electroweak scale (v). There exist several scenarios to explain this smallness of the neutrino masses. Among them, perhaps the most well-studied one is the conventional type-I seesaw mechanism [1]. In this mechanism, the smallness of the neutrino mass (m ν) can be obtained in an economic way at the expense of introducing heavy right-handed (RH) neutrinos (ν R). For values of Yukawa couplings involved (Y ν) of order unity, the mass scale of ν R (M R) turns out to be near the grand unified scale or so through the relation m ν ¼ −m D M R −1 m T D , where m D ¼ Y ν v. Although interesting, such a large scale is beyond the experimental reach. In this regard, the inverse seesaw mechanism [2-4] offers an interesting resolution through a double suppression by the new physics scale M through m ν ¼ m D M −1 μM T −1 m T D. With a small mass scale μ (of order keV to a few hundred MeV), a relatively low new physics scale (accessible to the LHC) associated with M results. However the main caveat of this scenario is to understand the smallness associated with μ, or in other words, how it is generated. Note that in the case of the type-I seesaw, the lepton number violation (LNV) happens through the Majorana mass term of the RH neutrinos, which is quite large. Contrary to this, in the case of the inverse seesaw, it happens via the μ term which is a tiny scale compared to the electroweak scale. As the lepton number is only an approximate symmetry of nature, it would be more natural to break it by a small amount rather than by a mass term like M R , which is very large. It can also be argued from the sense of 't Hooft [5], just because in the limit μ tends to zero, the m ν goes to zero and LNV vanishes so that the symmetry is enhanced. In this paper, we explain the desired smallness of the μ term in a flavor-symmetric framework. We consider the presence of a Δð27Þ flavor symmetry which is supplemented by additional Z 4 × Z 3 discrete groups. The structure guarantees the nonappearance of the μ term in the tree-level Lagrangian. In fact, it allows the μ term to be generated only through a significantly higher-dimensional operator, thereby suppressing the corresponding interaction by some nonzero powers of the cutoff scale (Λ) of the theory. There are flavon fields, whose vacuum expectation values (VEV) would break the flavor symmetry and thereby generate a specific structure of μ and other mass matrices, like the neutrino Dirac mass matrix (m D), charged leptons, etc. We will elaborate more on this as we proceed. In addition, we assume a 2-3 flavor symmetry as an additional symmetry of the Lagrangian (particularly for the lepton sector). The only place where this 2-3 symmetry will be broken is in the VEV alignment of a single flavon field (σ) responsible for generating the μ term. The VEV of all other flavons respect the 2-3 symmetry. So, in a way our framework suggests a unified source (through the μ term only) of breaking the 2-3 symmetry and lepton number violation. It is known [6] that a breaking of 2-3 symmetry may indicate a deviation from tribimaximal mixing (TBM) in the neutrino sector. Therefore in this work, we argue that the specific structure obtained for μ not only can explain the small masses of light neutrinos, but also accounts for the deviation from an exact tribimaximal mixing by having a nonzero θ 13 at the same time. In realizing the above goal, the fermion field content of the Standard Model (SM) is extended by adding three right-handed neutrinos ν R i (for i ¼ 1, 2, 3), and three SM gauge singlet fermions S i which have lepton number opposite that of the ν R i. In addition, the scalar sector is extended by adding a set of flavons that break the flavor symmetry around the few TeV scale or more. In Ref. [6], it was emphasized that both quark and lepton masses and also their mixing angles can be simultaneously accommodated in a framework of Δð27Þ based on the type-I seesaw mechanism. Here also we consider the quark sector.
DAE-BRNS, 2008
In order to explain the results in Eq.(l) one needs to go to a theory beyond the standard model (SM). Supersymmetry(SUSY) is an interesting possibility for new physics at TeV scale. There have been several proposals in recent times which attempt to explain the experimental data on neutrinos in the context of minimal supersymmetric standard model (MSSM) with bilinear and trilinear R-parity violation [2-4]. Due to R-parity violation the lightest supepparticle (LSP) is unstable forthis class ofmodels. However MSSM possesses the so-called "p-pioblem" l5l. related to the bilineart et^ p A, H in the MSSM superpotential. One ofthe solutions to The experimental results on neutrinos provide evidence of non-zero neutrino masses and mixing aneles. In this work we examine in detail the neulrino mass patterns and mixing angles in an extension of the minimal supersymmetiic standard model with three gauge-singlet neutrinos and R-parity violarion. The Majorana maises for the gauge-singlet neutrinos as well as the usual p-term for the Higgs Superfields are generated atthe electroweak scale through the vacuum expectation values ofthe singlet 6 n"rt.inor. The resulting effective mass matrix for the three light neutrinos have contributions from the seesaw mechanism involving the singlet neutrinos as well as due to the mixing with the heaq neutralinos. We show that evin with flavour diagonal neutrino Yukawa couplings the global data on three-flavour neutrinos can be well accounted for in this scenario at the tree level. We further study the decays ofthe lightest neutralino in this model. The lightest neutralino can be the lightest supersymmetric particte pSf;. We focus on different cases where the Iightest neutralino is either a bino or a higgsino or a gauge-singlei neutrino. We study the important phenomenological differences between these cases and find"out th"at certain ratios ofdecay branching ratios ofthe lightest neutralino are correlated with eitherthe solarorthe atmospheric (and reactor) neutrino angle. Neutrino oscillation experiments have confirmed nonzero masses and mixing-angles for neutrinos. Various experiments suggest that the mixing pattem of the three light neutrinos is bilarge, that isto say there are two large mixing angles and one small mixing angle. The data can be explained very well with the following set of mass squared differences and mixing angles at 3o c.L. ul 7.05 x 1o 5ev2 < Lml, ! 8.34 x 1o 5ev2, 2.07 x 10-3ev2 S Al-3r1 5, 2.75 x 10-3ev2, 30.39" I drz <37.46', 36.87' 51zt < 54.94", d13 < 13.69", (1) where L.m!, = mf; ml.
Prepared for submission to JHEP Neutrino mass from M Theory SO ( 10 )
2016
We study the origin of neutrino mass from SO(10) arising from M Theory compactified on a G2-manifold. This is linked to the problem of the breaking of the extra U(1) gauge group, in the SU(5)× U(1) subgroup of SO(10), which we show can achieved via a (generalised) Kolda-Martin mechanism. The resulting neutrino masses arise from a combination of the seesaw mechanism and induced R-parity breaking contributions. The rather complicated neutrino mass matrix is analysed for one neutrino family and it is shown how phenomenologically acceptable neutrino masses can emerge.
Seesaw fermion masses in an SO (10) grand unified theory
Physical Review …, 2006
In this work we study an SO(10) GUT model with minimum Higgs representations belonging only to the 210 and 16 dimensional representations of SO(10). We add a singlet fermion S in addition to the usual 16 dimensional representation containing quarks and leptons. There are no Higgs bi-doublets and so charged fermion masses come from one-loop corrections. Consequently all the fermion masses, Dirac and Majorana, are of the seesaw type. We minimize the Higgs potential and show how the left-right symmetry is broken in our model where it is assumed that a D-parity odd Higgs field gets a vacuum expectation value at the grand unification scale. From the renormalization group equations we infer that in our model unification happens at 10 15 GeV and left-right symmetry can be extended up to some values just above 10 11 GeV. The Yukawa sector of our model is completely different from most of the standard grand unified theories and we explicitly show how the Yukawa sector will look like in the different phases and briefly comment on the running of the top quark mass. We end with a brief analysis of lepton number asymmetry generated from the interactions in our model.
Neutrino oscillations in a supersymmetric SO(10) model with type-III see-saw mechanism
Journal of High Energy Physics, 2005
The neutrino oscillations are studied in the framework of the minimal supersymmetric SO(10) model with Type-III seesaw mechanism by additionally introducing a number of SO(10) singlet neutrinos. The light Majorana neutrino mass matrix is given by a combination of those of the singlet neutrinos and the SU (2) L active neutrinos. The minimal SO(10) model gives an unambiguous Dirac neutrino mass matrix, which enables us to predict the masses and the other parameters for the singlet neutrinos. These predicted masses take the values accessible and testable by near future collider experiments under the reasonable assumptions. More comprehensive calculations on these parameters are also given.
A little Higgs model of neutrino masses
Physics Letters B, 2005
Little Higgs models are formulated as effective theories with a cut-off of up to 100 times the electroweak scale. Neutrino masses are then a puzzle, since the usual see-saw mechanism involves a much higher scale that would introduce quadratic corrections to the Higgs mass parameter. We propose a model that can naturally accommodate the observed neutrino masses and mixings in Little Higgs scenarios. Our framework does not involve any large scale or suppressed Yukawa couplings, and it implies the presence of three extra (Dirac) neutrinos at the TeV scale. The masses of the light neutrinos are induced radiatively, they are proportional to small (≈ keV) mass parameters that break lepton number and are suppressed by the Little Higgs cut-off.