NEUTRINO SPECTRUM IN NONSUPERSYMMETRIC SO(10)

1996 ◽  
Vol 11 (36) ◽  
pp. 2837-2848
Author(s):  
GABRIELA BARENBOIM
Keyword(s):  
Higgs Sector ◽  
Fine Tuning ◽  
Hierarchy Problem ◽  
Yukawa Couplings ◽  
Neutrino Spectrum ◽  
Fermion Masses ◽  
Mass Matrices

We present a predictive scheme for fermion masses and mixings inspired by nonsupersymmetric SO(10) in which the hierarchy problem is resolved without fine tuning the Yukawa couplings. This calls for a nonminimal Higgs sector which we exploit in deriving the expressions for the mass matrices. To keep the predictivity of the model under control we limit the structure of the mass matrices by imposing U(1) symmetries. A very predictive neutrino spectrum is then obtained.

THE FERMION MASSES IN E6

1998 ◽  
Vol 13 (09) ◽  
pp. 685-693
Author(s):  
H. AKCAY
Keyword(s):  
Mass Spectrum ◽  
Grand Unification ◽  
Neutrino Masses ◽  
Yukawa Couplings ◽  
Neutrino Spectrum ◽  
Fermion Masses ◽  
The Masses

We investigate a particular breaking chain of the grand unification group E6. With two smallest Higgs multiplets that have Yukawa couplings to fermions, we obtain a reasonable mass spectrum for fermions. The neutrino masses are expressed in terms of the masses of the charged fermions, leading to a predictive neutrino spectrum.

scholarly journals Higgs flavor phenomenology in a supersymmetric left-right model with parity

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Syuhei Iguro ◽  
Junichiro Kawamura ◽  
Yuji Omura ◽  
Yoshihiro Shigekami
Keyword(s):  
Higgs Mass ◽  
Fine Tuning ◽  
Tree Level ◽  
Supersymmetric Model ◽  
Parameter Region ◽  
Yukawa Couplings ◽  
Lepton Flavor ◽  
Flavor Changing ◽  
Fermion Masses ◽  
The Standard Model

Abstract In this paper, we focus on the supersymmetric model with left-right (LR) symmetry, that is especially proposed in our previous work [1]. In this model, there are four Higgs doublets in order to realize the Standard Model (SM) fermion masses and the Cabibbo-Kobayashi-Maskawa matrix. The heavy Higgs doublets unavoidably have flavor changing couplings to the SM fermions and induce flavor-changing neutral currents at tree level. We study broader parameter space than the previous work with including the renormalization group corrections to the Yukawa couplings between the LR breaking scale, $$ \mathcal{O} $$ O (1013) GeV, and the supersymmetry breaking scales, $$ \mathcal{O} $$ O (100) TeV. The CP violating observable in K–$$ \overline{K} $$ K ¯ mixing, ϵK, strongly constrains the model, so that heavy Higgs mass should be heavier than $$ \mathcal{O} $$ O (100) TeV. We study the lepton flavor violating (LFV) processes setting heavy Higgs masses to be 170 TeV. The branching ratios of μ → 3e and the μ–e conversion can be larger than 10−16 that could be covered by the future experiments. We also study the degree of fine-tuning in the parameter region that predicts testable LFV processes.

GSW model of electroweak interactions

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Gauge Symmetry ◽  
Higgs Sector ◽  
Electroweak Interactions ◽  
Hierarchy Problem ◽  
Fermion Masses ◽  
Electroweak Sector ◽  
Higgs Effect

The electroweak sector of the SM described by an SUL(2)UY(1) gauge symmetry which is broken spontaneously to Uem(1) is introduced. The generation of boson and fermion masses by the Higgs effect is discussed. The properties of the Higgs sector are examined. The conditions for decoupling and the hierarchy problem are discussed.

scholarly journals A REVIEW OF THREE-FAMILY GRAND UNIFIED STRING MODELS

1998 ◽  
Vol 13 (15) ◽  
pp. 2551-2598 ◽  
Author(s):  
ZURAB KAKUSHADZE ◽  
GARY SHIU ◽  
S.-H. HENRY TYE ◽  
YAN VTOROV-KAREVSKY
Keyword(s):  
Supersymmetry Breaking ◽  
Fine Tuning ◽  
Tree Level ◽  
Hierarchy Problem ◽  
Triplet Splitting ◽  
Mass Matrices ◽  
String Models ◽  
Proton Stability ◽  
Breaking Scale

We review the construction and classification of three-family grand unified models within the framework of asymmetric orbifolds in perturbative heterotic superstring. We give a detailed survey of all such models which is organized to aid analysis of their phenomenological properties. We compute tree level superpotentials for these models. These superpotentials are used to analyze the issues of proton stability (doublet–triplet splitting and R-parity-violating terms) and Yukawa mass matrices. To have agreement with phenomenological data all these models seem to require a certain degree of fine-tuning. We also analyze the possible patterns of supersymmetry breaking in these models. We find that the supersymmetry breaking scale comes out either too high to explain the electroweak hierarchy problem, or below the electroweak scale unless some degree of fine-tuning is involved. Thus, none of the models at hand seem to be phenomenologically flawless.

scholarly journals Higgs Bosons Near 125 GeV in the NMSSM with Constraints at the GUT Scale

2012 ◽  
Vol 2012 ◽  
pp. 1-18 ◽  
Author(s):  
Ulrich Ellwanger ◽  
Cyril Hugonie
Keyword(s):  
Higgs Boson ◽  
Cross Section ◽  
Parameter Space ◽  
Yukawa Coupling ◽  
Higgs Sector ◽  
Susy Breaking ◽  
Higgs Bosons ◽  
Fine Tuning ◽  
Yukawa Couplings ◽  
Gut Scale

We study the NMSSM with universal Susy breaking terms (besides the Higgs sector) at the GUT scale. Within this constrained parameter space, it is not difficult to find a Higgs boson with a mass of about 125 GeV and an enhanced cross-section in the diphoton channel. An additional lighter Higgs boson with reduced couplings and a mass≲123 GeV is potentially observable at the LHC. The NMSSM-specific Yukawa couplingsλandκare relatively large and tanβis small, such thatλ,κ, and the top Yukawa coupling are of𝒪(1)at the GUT scale. The lightest stop can be as light as 105 GeV, and the fine-tuning is modest. WMAP constraints can be satisfied by a dominantly Higgsino-like LSP with substantial bino, wino, and singlino admixtures and a mass of~60–90 GeV, which would potentially be detectable by XENON100.

scholarly journals THE PROBLEM OF NEUTRINO MASSES IN EXTENSIONS OF THE STANDARD MODEL

2001 ◽  
Vol 16 (32) ◽  
pp. 5101-5199 ◽  
Author(s):  
ISABELLA MASINA
Keyword(s):  
Proton Decay ◽  
Fine Tuning ◽  
Neutrino Masses ◽  
Flavor Symmetry ◽  
Mixing Angle ◽  
Grand Unified Theories ◽  
Triplet Splitting ◽  
Fermion Masses ◽  
The Standard Model ◽  
Neutrino Masses And Mixings

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.

scholarly journals Higgs sector and fine-tuning in the phenomenological MSSM

2012 ◽  
Vol 86 (7) ◽  
Author(s):  
Matthew W. Cahill-Rowley ◽  
JoAnne L. Hewett ◽  
Ahmed Ismail ◽  
Thomas G. Rizzo
Keyword(s):  
Higgs Sector ◽  
Fine Tuning

scholarly journals Fermion mass hierarchies from supersymmetric gauged flavour symmetry in 5D

2021 ◽  
Vol 10 (6) ◽  
Author(s):  
Ketan Patel
Keyword(s):  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Fermion Mass ◽  
Order Unity ◽  
Anomaly Cancellation ◽  
Fundamental Parameters ◽  
Yukawa Couplings ◽  
Fifth Dimension ◽  
Fermion Masses ◽  
The Masses

A mechanism to generate realistic fermion mass hierarchies based on supersymmetric gauged U(1)_FU(1)F symmetry in flat five-dimensional (5D) spacetime is proposed. The fifth dimension is compactified on S^1/Z_2S1/Z2 orbifold. The standard model fermions charged under the extra abelian symmetry along with their superpartners live in the 5D bulk. Bulk masses of fermions are generated by the vacuum expectation value of N=2N=2 superpartner of U(1)_FU(1)F gauge field, and they are proportional to U(1)_FU(1)F charges of respective fermions. This decides localization of fermions in the extra dimension, which in turn gives rise to exponentially suppressed Yukawa couplings in the effective 4D theory. Anomaly cancellation puts stringent constraints on the allowed U(1)_FU(1)F charges which leads to correlations between the masses of quarks and leptons. We perform an extensive numerical scan and obtain several solutions for anomaly-free U(1)_FU(1)F, which describe the observed pattern of fermion masses and mixing with all the fundamental parameters of order unity. It is found that the possible existence of SM singlet neutrinos substantially improves the spectrum of solutions by offering more freedom in choosing U(1)_FU(1)F charges. The model predicts Z^\primeZ′ boson mediating flavour violating interactions in both the quark and lepton sectors with the couplings which can be explicitly determined from the Yukawa couplings.

scholarly journals Searches for Direct Pair Production of Third Generation Squarks with the ATLAS Detector

2018 ◽  
Vol 46 ◽  
pp. 1860057
Author(s):  
Federico Meloni
Keyword(s):  
Standard Model ◽  
Pair Production ◽  
Higgs Sector ◽  
Fine Tuning ◽  
Proton Collision ◽  
Third Generation ◽  
Proton Proton ◽  
Missing Transverse Momentum ◽  
Model Hierarchy ◽  
Generation Squarks

This document summarises recent ATLAS results for searches for third generation squarks using 36.1 [Formula: see text] of LHC proton-proton collision data collected at [Formula: see text] TeV. Despite the absence of experimental evidence, weak scale supersymmetry remains one of the best motivated and studied Standard Model extensions. Supersymmetry can naturally solve the Standard Model hierarchy problem by preventing a large fine-tuning in the Higgs sector: a typical natural SUSY spectrum contains light third generation squarks (stops and sbottoms). Both R-Parity conserving and R-Parity violating scenarios are considered. The searches involve final states including jets, missing transverse momentum, electrons or muons. Simplified models predicting pair production of third generation squarks have been excluded at 95% CL up to about one TeV in the most favourable scenarios.

scholarly journals A KIND OF PREDICTION FROM STRING PHENOMENOLOGY: EXTRA MATTER AT LOW ENERGY

2007 ◽  
Vol 22 (14) ◽  
pp. 989-1003 ◽  
Author(s):  
CARLOS MUÑOZ
Keyword(s):  
Potential Problem ◽  
Low Energy ◽  
Mixing Angles ◽  
Yukawa Couplings ◽  
Problem Finding ◽  
String Phenomenology ◽  
Fermion Masses ◽  
Interesting Pattern ◽  
Low Energies ◽  
Crucial Ingredient

We review the possibility that the Supersymmetric Standard Model arises from orbifold constructions of the E8×E8 Heterotic Superstring, and the phenomenological properties that such a model should have. In particular, trying to solve the discrepancy between the unification scale predicted by the Heterotic Superstring (≈g GUT × 5.27 × 1017 GeV ) and the value deduced from LEP experiments (≈2 × 1016 GeV ), we will predict the presence at low energies of three families of Higgses and vector-like colour triplets. Our approach relies on the Fayet–Iliopoulos breaking, and this is also a crucial ingredient, together with having three Higgs families, to obtain in these models an interesting pattern of fermion masses and mixing angles at the renormalizable level. Namely, after the gauge breaking some physical particles appear combined with other states, and the Yukawa couplings are modified in a well-controlled way. On the other hand, dangerous flavour-changing neutral currents may appear when fermions of a given charge receive their mass through couplings with several Higgs doublets. We will address this potential problem, finding that viable scenarios can be obtained for a reasonable light Higgs spectrum.

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