Neutrinos, their partners, and unification (original) (raw)

Small neutrino masses and gauge coupling unification

Physical Review D, 2015

The physics responsible for gauge coupling unification may also be responsible for providing small neutrino masses. We present a model based on the SU (3)C ⊗ SU (3)L ⊗ U (1)X (3-3-1) gauge group in which neutrinos are massless at tree-level. Gauge mediated radiative corrections generate calculable neutrino masses. The three gauge coupling constants unify for a 3-3-1 scale of order TeV, making the model directly testable at the LHC.

A simple grand unification view of neutrino mixing and fermion mass matrices

Physics Letters B, 1999

Assuming three light neutrinos and the see-saw mechanism we present a semiquantitative model of fermion masses based on (SUSY) SU(5) and abelian horizontal charges. A good description of the observed pattern of quark and lepton masses is obtained. For neutrinos we naturally obtain widely split masses and large atmospheric neutrino mixing as a consequence of SU(5)-related asymmetric mass matrices for d quarks and charged leptons.

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.

Neutrinos and gauge unification

Physical Review D, 2001

The approximate unification of gauge couplings is the best indirect evidence for low-energy supersymmetry, although it is not perfect in its simplest realizations. Given the experimental evidence for small non-zero neutrino masses, it is plausible to extend the MSSM with three right-handed neutrino chiral multiplets, with large Majorana masses below the unification scale, so that a see-saw mechanism can be implemented. In this extended MSSM, the unification prediction for the strong gauge coupling constant at MZ can be lowered by up to ∼ 5%, bringing it closer to the experimental value at 1σ, therefore improving significantly the accuracy of gauge coupling unification.

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.

Grand unification of the sterile neutrino

Physics Letters B, 1998

The simplest way to simultaneously understand all existing indications of neutrino oscillations from solar and atmospheric neutrino deficits and the LSND experiment, seems to be to postulate a sterile neutrino. We present a realistic grand unified model based on the gauge group SO(10) × SO(10) ′ that leads to the desired masses and mixings for the sterile and the known neutrinos needed to understand the above observations while fitting those of the known charged fermions. The model is a grand unified realization of the recently proposed idea that the sterile neutrino is the lightest neutrino of a mirror sector of the universe which has identical matter and gauge content as the standard model. The two SO(10)'s operate on the two sectors in a mirror symmetric way and are connected by a mixed Higgs representations whose net effect is to connect the superheavy right handed neutrinos of the two sectors.

Status and implications of neutrino masses: A brief panorama

International Journal of Modern Physics a, 2015

With the historic discovery of the Higgs boson our picture of particle physics would have been complete were it not for the neutrino sector and cosmology. I briefly discuss the role of neutrino masses and mixing upon gauge coupling unification, electroweak breaking and the flavor sector. Time is ripe for new discoveries such as leptonic CP violation, charged lepton flavor violation and neutrinoless double beta decay. Neutrinos could also play a role in elucidating the nature of dark matter and cosmic inflation.