A model that underlies the Standard model (original) (raw)
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Neutrino Masses from Generalized Symmetry Breaking
2024
We explore generalized global symmetries in theories of physics beyond the standard model. Theories of Z 0 bosons generically contain "noninvertible" chiral symmetries, whose presence indicates a natural paradigm to break this symmetry by an exponentially small amount in an ultraviolet completion. For example, in models of gauged lepton family difference such as the phenomenologically well motivated Uð1Þ L μ −L τ , there is a noninvertible lepton number symmetry which protects neutrino masses. We embed these theories in gauged non-Abelian horizontal lepton symmetries, e.g., Uð1Þ L μ −L τ ⊂ SUð3Þ H , where the generalized symmetries are broken nonperturbatively by the existence of lepton family magnetic monopoles. In such theories, either Majorana or Dirac neutrino masses may be generated through quantum gauge theory effects from the charged lepton Yukawas, e.g., y ν ∼ y τ expð−S inst Þ. These theories require no bevy of new fields nor ad hoc additional global symmetries but are instead simple, natural, and predictive: The discovery of a lepton family Z 0 at low energies will reveal the scale at which L μ − L τ emerges from a larger gauge symmetry.
The Problem of Neutrino Masses in Extensions of the Standard Model
International Journal of Modern Physics A, 2001
We review the problem of neutrino masses and mixings in the context of grand unified theories. After a brief summary of the present experimental status of neutrino physics, we describe how the see-saw mechanism can automatically account for the large atmospheric mixing angle. We provide two specific examples where this possibility is realized by means of a flavor symmetry. We then review in some detail the various severe problems which plague minimal GUT models (like the doublet–triplet splitting and proton-decay) and which force us to investigate the possibility of constructing more elaborate but realistic models. We then show an example of a quasirealistic SUSY SU(5) model which, by exploiting the crucial presence of an Abelian flavor symmetry, does not require any fine-tuning and predicts a satisfactory phenomenology with respect to coupling unification, fermion masses and mixings and bounds from proton decay.
arXiv: High Energy Physics - Phenomenology, 2013
We propose a 3-3-1 model where the SU(3)CotimesSU(3)LotimesU(1)XSU(3)_{C}\otimes SU(3)_{L}\otimes U(1)_{X}SU(3)CotimesSU(3)LotimesU(1)X symmetry is extended by S3otimesZ3otimesZ3primeotimesZ8otimesZ16S_{3}\otimes Z_{3}\otimes Z_{3}^{\prime }\otimes Z_{8}\otimes Z_{16}S3otimesZ3otimesZ3primeotimesZ8otimesZ16 and the scalar spectrum is enlarged by extra % SU(3)_{L} singlet scalar fields. The model successfully describes the observed SM fermion mass and mixing pattern. In this framework, the light active neutrino masses arise via an inverse seesaw mechanism and the observed charged fermion mass and quark mixing hierarchy is a consequence of the Z3otimesZ3primeotimesZ8otimesZ16Z_{3}\otimes Z_{3}^{\prime }\otimes Z_{8}\otimes Z_{16}Z3otimesZ3primeotimesZ8otimesZ16 symmetry breaking at very high energy. The obtained physical observables for both quark and lepton sectors are compatible with their experimental values. The model predicts the effective Majorana neutrino mass parameter of neutrinoless double beta decay to be mbetabeta=m_{\beta \beta }=mbetabeta= 4 and 48 meV for the normal and the inverted neutrino spectra, respectively. Furthermore, we found a leptonic Dirac CP violating phase close ...
A new, direct link between the baryon asymmetry and neutrino masses
Nuclear Physics B, 2009
We point out that, in a class of SO(10) models with matter fields in 16 and 10 representations and type II realization of the seesaw mechanism, the light neutrino masses and the CP asymmetry needed for leptogenesis are controlled by one and the same set of couplings. The generated baryon asymmetry then directly depends on the low-energy neutrino parameters, with no unknown seesaw-scale flavour parameters involved; in particular, the necessary CP violation is provided by the CP-violating phases of the lepton mixing matrix. We compute the CP asymmetry in triplet decays for this scenario and show that it can lead to successful leptogenesis.
Combined flavor symmetry violation and lepton number violation in neutrino physics
Physical Review D, 2006
Heavy singlet neutrinos admit Majorana masses which are not possible for the Standard Model particles. This suggest new possibilities for generating the masses and mixing angles of light neutrinos. We present a model of neutrino physics which combines the source of lepton number violation with the flavor symmetry responsible for the hierarchy in the charged lepton and quark sector. This is accomplished by giving the scalar field effecting the lepton number violation a nonzero charge under the horizontal flavor symmetry. We find an economical model which is consistent with the measured values of the atmospheric and solar neutrino mass-squares and mixing angles.
Left-right symmetric theory with light sterile neutrinos
Physical Review D, 2013
A simple theoretical framework for the spontaneous breaking of parity, and baryon and lepton numbers is proposed. In this context, the baryon and lepton numbers are independent local gauge symmetries, while parity is defined making use of the left-right symmetry. We show that in the minimal model the new leptoquark fields needed to define an anomaly-free theory also generate neutrino masses through the type III seesaw mechanism. The spectrum of neutrinos and some phenomenological aspects are discussed. This theory predicts the possible existence of two light sterile neutrinos.
Physical Review D, 2017
We propose a model to explain tiny masses of neutrinos with the lepton number conservation, where neither too heavy particles beyond the TeV-scale nor tiny coupling constants are required. Assignments of conserving lepton numbers to new fields result in an unbroken Z 2 symmetry that stabilizes the dark matter candidate (the lightest Z 2-odd particle). In this model, Z 2-odd particles play an important role to generate the mass of neutrinos. The scalar dark matter in our model can satisfy constraints on the dark matter abundance and those from direct searches. It is also shown that the strong first-order phase transition, which is required for the electroweak baryogenesis, can be realized in our model. In addition, the scalar potential can in principle contain CP-violating phases, which can also be utilized for the baryogenesis. Therefore, three problems in the standard model, namely absence of neutrino masses, the dark matter candidate, and the mechanism to generate baryon asymmetry of the Universe, may be simultaneously resolved at the TeV-scale. Phenomenology of this model is also discussed briefly.
Flavor symmetries, leptogenesis and the absolute neutrino mass scale
Journal of High Energy Physics, 2009
We study the interplay between flavor symmetries and leptogenesis in the case when the scale of flavor symmetry breaking is higher than the scale at which lepton number is violated. We show that when the heavy Majorana neutrinos belong to an irreducible representation of the flavor group, all the leptogenesis CP asymmetries vanish in the limit of exact symmetry. In the case of reducible representations we identify a general condition that, if satisfied, guarantees the same result. We then focus on the case of a model in which an A 4 flavor symmetry yields a drastic reduction in the number of free parameters, implying that at leading order several quantities are only a function of the lightest neutrino mass m l , which in turn is strongly constrained. For normal ordering (NO) we find m l ≃ (0.0044 ÷ 0.0056) eV while for inverted ordering (IO) m l 0.017 eV. For the 0ν2β decay parameter this yields |m ee | ≃ (0.006 ÷ 0.007) eV (NO) and |m ee | > ∼ 0.017 eV (IO). We show that the leptogenesis CP asymmetries only depend on m l , on a single non-hierarchical Yukawa coupling y, and on two parameters that quantify the flavor symmetry breaking effects, and we argue that the unflavored regime for leptogenesis is strongly preferred in our model, thus realizing a rather predictive scenario. Performing a calculation of the matter-antimatter asymmetry we find that for NO the observed value is easily reproduced for natural values of the symmetry breaking parameters. For IO successful leptogenesis is possible for a limited choice of the parameters implying rather large reheating temperatures T reh 5 × 10 13 GeV.
The European Physical Journal C, 2007
We construct an extension of the supersymmetric standard model where both CP symmetry and R-parity are spontaneously broken. We study the electroweak symmetry breaking sector of the model and find minima consistent with the experimental bounds on Higgs boson masses. Neutrino masses and mixing angles are generated through both seesaw and bilinear R-parity violation. We show that the hierarchical mass pattern is obtained, and mixings are consistent with measured values. Due to the spontaneous CP and R-parity violation, the neutrino sector is CP violating, and we calculate the corresponding phase. We further restrict the parameter space to agree with the limits on the electric dipole moment of the neutron. Finally, we study the CP violation parameter K in the kaon system and show that we obtain results consistent with the experimental value. arXiv:0705.4160v1 [hep-ph] 29 May 2007 2 M. Frank, K. Huitu, T. Rüppell: Higgs and neutrino sector in a spontaneous CP and R breaking model Another problem of the Standard Model, which persists in the MSSM, is that the neutrino masses vanish. Yet the neutrino experiments have provided strong evidence for small nonvanishing neutrino masses . Perhaps the most popular mechanism to explain neutrino masses is the seesaw mechanism , which can generate small masses for neutrinos by allowing Majorana masses through the introduction of heavy right-handed neutrinos. Another popular way to explain the neutrino masses is through a small violation of R-parity [16], R p = (−1) 3B−L+2s , where B=baryon number, L=lepton number, and s=spin of the particle . Extensive phenomenological studies of R-parity violating effects exist; for a recent review see .