scholarly journals NEW GAUGE BOSONS FROM STRING MODELS

1996 ◽  
Vol 11 (15) ◽  
pp. 1247-1262 ◽  
Author(s):  
MIRJAM CVETIČ ◽  
PAUL LANGACKER
Keyword(s):  
Standard Model ◽  
Supersymmetry Breaking ◽  
Large Class ◽  
Top Quark ◽  
Fine Tuning ◽  
Electroweak Symmetry ◽  
Gauge Bosons ◽  
Exotic Particles ◽  
Yukawa Couplings ◽  
String Models

We address the mass ranges of new neutral gauge bosons and constraints on the accompanying exotic particles as predicted by a class of superstring models. Under certain assumptions about the supersymmetry breaking parameters we show that breaking of an additional U(1)′ symmetry is radiative when the appropriate Yukawa couplings of exotic particles are of order one, analogous to the radiative breaking of the electroweak symmetry in the supersymmetric standard model due to the large top-quark Yukawa coupling. Such large Yukawa couplings occur for a large class of string models. The Z′ and exotic masses are either of [Formula: see text], or of a scale intermediate between the string and electroweak scales. In the former case, [Formula: see text] may be achieved without excessive fine-tuning, and is within future experimental reach.

scholarly journals The Clockwork Standard Model

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Yoo-Jin Kang ◽  
Soonbin Kim ◽  
Hyun Min Lee
Keyword(s):  
Standard Model ◽  
Mass Parameter ◽  
Planck Scale ◽  
Fine Tuning ◽  
Mass Hierarchy ◽  
Gauge Bosons ◽  
Five Dimensions ◽  
Expansion Parameter ◽  
Bulk Mass ◽  
Linear Dilaton

Abstract We consider various bulk fields with general dilaton couplings in the linear dilaton background in five dimensions as the continuum limit of clockwork models. We show that the localization of the zero modes of bulk fields and the mass gap in the KK spectrum depend not only on the bulk dilaton coupling, but also on the bulk mass parameter in the case of a bulk fermion. The consistency from universality and perturbativity of gauge couplings constrain the dilaton couplings to the brane-localized matter fields as well as the bulk gauge bosons. Constructing the Clockwork Standard Model (SM) in the linear dilaton background, we provide the necessary conditions for the bulk mass parameters for explaining the mass hierarchy and mixing for the SM fermions. We can introduce a sizable expansion parameter ε = $$ {e}^{-\frac{2}{3}{kz}_c} $$ e − 2 3 kz c for the realistic flavor structure in the quark sector without a fine-tuning in the bulk mass parameters, but at the expense of a large 5D Planck scale. On the other hand, we can use a smaller expansion parameter for lepton masses, in favor of the solution to the hierarchy problem of the Higgs mass parameter. We found that massive Kaluza-Klein (KK) gauge bosons and massive KK gravitons couple more strongly to light and heavy fermions, respectively, so there is a complementarity in the resonance researches for those KK modes at the LHC.

scholarly journals A SUPERSYMMETRIC MODEL WITH THE GAUGE SYMMETRY SU(3)1 × SU(2)1 × U(1)1 × SU(3)2 × SU(2)2 × U(1)2

2003 ◽  
Vol 18 (14) ◽  
pp. 967-975 ◽  
Author(s):  
J. G. KÖRNER ◽  
CHUN LIU
Keyword(s):  
Gauge Symmetry ◽  
Standard Model ◽  
Symmetry Breaking ◽  
Supersymmetry Breaking ◽  
Simple Form ◽  
Electroweak Symmetry Breaking ◽  
Supersymmetric Model ◽  
Electroweak Symmetry ◽  
Gauge Groups ◽  
The Standard Model

A supersymmetric model with two copies of the Standard Model gauge groups is constructed in the gauge mediated supersymmetry breaking scenario. The supersymmetry breaking messengers are in a simple form. The Standard Model is obtained after first step gauge symmetry breaking. In the case of one copy of the gauge interactions being strong, a scenario of electroweak symmetry breaking is discussed, and the gauginos are generally predicted to be heavier than the sfermions.

scholarly journals THE LIMITS OF CUSTODIAL SYMMETRY

2010 ◽  
Vol 25 (27n28) ◽  
pp. 5082-5096
Author(s):  
R. SEKHAR CHIVUKULA ◽  
ROSHAN FOADI ◽  
ELIZABETH H. SIMMONS ◽  
STEFANO DI CHIARA
Keyword(s):  
Standard Model ◽  
Top Quark ◽  
Quark Mass ◽  
Electroweak Symmetry ◽  
Top Quark Mass ◽  
Particle Content ◽  
Dirac Mass ◽  
The Standard Model ◽  
Custodial Symmetry ◽  
Weak Doublet

We introduce a toy model implementing the proposal of using a custodial symmetry to protect the [Formula: see text] coupling from large corrections. This "doublet-extended standard model" adds a weak doublet of fermions (including a heavy partner of the top quark) to the particle content of the standard model in order to implement an O(4) × U(1)X ~ SU(2)L × SU(2)R × PLR × U(1)X symmetry in the top-quark mass generating sector. This symmetry is softly broken to the gauged SU(2)L × U(1)Y electroweak symmetry by a Dirac mass M for the new doublet; adjusting the value of M allows us to explore the range of possibilities between the O(4)-symmetric (M → 0) and standard-model-like (M → ∞) limits.

scholarly journals DYNAMICAL ELECTROWEAK SYMMETRY BREAKING IN STRING MODELS WITH D-BRANES

2010 ◽  
Vol 25 (13) ◽  
pp. 2679-2698 ◽  
Author(s):  
NORIAKI KITAZAWA
Keyword(s):  
Symmetry Breaking ◽  
Strong Coupling ◽  
Higgs Doublet ◽  
Electroweak Symmetry Breaking ◽  
Kinetic Term ◽  
Electroweak Symmetry ◽  
Gauge Bosons ◽  
S Parameter ◽  
String Models ◽  
Gauge Interaction

The possibility of dynamical electroweak symmetry breaking by strong coupling gauge interaction in models with D-branes in String Theory is examined. Instead of elementary scalar Higgs doublet fields, the gauge symmetry with strong coupling (technicolor) is introduced. As the first step of this direction, a toy model, which is not fully realistic, is concretely analyzed in some detail. The model consists of D-branes and anti-D-branes at orbifold singularities in (T2 × T2 × T2)/Z3 which preserves supersymmetry. Supersymmetry is broken through the brane supersymmetry breaking. It is pointed out that the problem of large S parameter in dynamical electroweak symmetry breaking scenario may be solved by natural existence of kinetic term mixings between hypercharge U(1) gauge boson and massive anomalous U(1) gauge bosons. The problems to be solved toward constructing more realistic models are clarified in the analysis.

scholarly journals FLIPPED SU(5), SEESAW SCALE PHYSICS AND DEGENERATE VACUA

2006 ◽  
Vol 21 (14) ◽  
pp. 1151-1160 ◽  
Author(s):  
C. R. DAS ◽  
C. D. FROGGATT ◽  
L. V. LAPERASHVILI ◽  
H. B. NIELSEN
Keyword(s):  
Standard Model ◽  
Effective Potential ◽  
Top Quark ◽  
Multiple Point ◽  
Yukawa Couplings ◽  
Fundamental Scale ◽  
Loop Approximation ◽  
The Standard Model ◽  
Gut Scale ◽  
The One

We investigate the requirement of the existence of two degenerate vacua of the effective potential as a function of the Weinberg–Salam Higgs scalar field norm, as suggested by the multiple point principle, in an extension of the Standard Model including seesaw scale physics. Results are presented from an investigation of an extension of the Standard Model to the gauge symmetry group SU (3)C× SU (2)L× U (1)′×Ũ(1), where U (1)′ and Ũ(1) originate at the seesaw scale M SS , when heavy (right-handed) neutrinos appear. The consequent unification of the group SU (3)C× SU (2)L× U (1)′ into the flipped SU (5) at the GUT scale leads to the group SU (5)×Ũ(1). We assume the position of the second minimum of the effective potential coincides with the fundamental scale, here taken to be the GUT scale. We solve the renormalization group equations in the one-loop approximation and obtain a top-quark mass of 171±3 GeV and a Higgs mass of 129±4 GeV , in the case when the Yukawa couplings of the neutrinos are less than half that of the top quark at the GUT scale.

scholarly journals Doublet–singlet model and unitarity

2016 ◽  
Vol 31 (01) ◽  
pp. 1650013 ◽  
Author(s):  
G. Cynolter ◽  
J. Kovács ◽  
E. Lendvai
Keyword(s):  
Dark Matter ◽  
Mass Spectrum ◽  
Scattering Amplitudes ◽  
Standard Model ◽  
Dark Matter Candidate ◽  
Particle Scattering ◽  
Gauge Bosons ◽  
Yukawa Couplings ◽  
The Standard Model ◽  
Blind Spots

We study the renormalizable singlet–doublet fermionic extension of the Standard Model (SM). In this model, the new vector-like fermions couple to the gauge bosons and to the Higgs via new Yukawa couplings that allow for nontrivial mixing in the new sector, providing a stable, neutral dark matter candidate. Approximate analytic formulae are given for the mass spectrum around the blind spots, where the dark matter candidate coupling to h or Z vanishes. We calculate the two particle scattering amplitudes in the model, impose the perturbative unitarity constraints and establish bounds on the Yukawa couplings.

NARROW-RESONANCE IN e−e− SCATTERING DUE TO ADDITIONAL GAUGE BOSON

1996 ◽  
Vol 11 (09) ◽  
pp. 1621-1625 ◽  
Author(s):  
PAUL H. FRAMPTON
Keyword(s):  
Standard Model ◽  
Top Quark ◽  
Quark Mass ◽  
Special Role ◽  
Top Quark Mass ◽  
Narrow Resonance ◽  
Gauge Bosons ◽  
The Third ◽  
High Energies ◽  
The Standard Model

It now appears phenomenologically that the third family may be essentially different from the first two. Particularly the high value of the top quark mass suggests a special role. In the standard model all three families are treated similarly [becoming exactly the same at asymptotically high energies] so I need to extend the model to accommodate the goal of a really different third family. In this article I describe one such viable extension, the 331 model which predicts bileptonic gauge bosons.

VACUUM ALIGNMENT IN THE TOP MODE STANDARD MODEL

1991 ◽  
Vol 06 (40) ◽  
pp. 3691-3696
Author(s):  
NORIAKI KITAZAWA
Keyword(s):  
Standard Model ◽  
Symmetry Breaking ◽  
Effective Potential ◽  
Top Quark ◽  
Ladder Approximation ◽  
Electroweak Symmetry Breaking ◽  
Electroweak Symmetry ◽  
Vacuum Alignment

We study the vacuum alignment in the top mode Standard Model in which the electroweak symmetry breaking is triggered by the top quark condensation. Including the QCD effects through the Cornwall-Jackiw-Tomboulis effective potential, we establish that the correct electroweak symmetry breaking SU (2)L × U (1)Y → U (1) em occurs in this model in 1/N leading and improved ladder approximation.

scholarly journals MINIMAL FLAVOR CONSTRAINTS FOR TECHNICOLOR

2010 ◽  
Vol 25 (20) ◽  
pp. 3911-3932 ◽  
Author(s):  
HIDENORI S. FUKANO ◽  
FRANCESCO SANNINO
Keyword(s):  
Standard Model ◽  
Symmetry Breaking ◽  
Vacuum Polarization ◽  
Electroweak Symmetry Breaking ◽  
Strong Impact ◽  
Electroweak Symmetry ◽  
Minimal Set ◽  
Gauge Bosons ◽  
Higher Dimensional ◽  
The Standard Model

We analyze the constraints on the the vacuum polarization of the Standard Model gauge bosons from a minimal set of flavor observables valid for a general class of models of dynamical electroweak symmetry breaking. We will show that the constraints have a strong impact on the self-coupling and masses of the lightest spin-one resonances. Our analysis is applicable to any four and higher-dimensional extension of the Standard Model reducing to models of dynamical electroweak symmetry breaking.

scholarly journals Radiative electroweak symmetry breaking beyond leading logarithms

2006 ◽  
Vol 84 (6-7) ◽  
pp. 545-550
Author(s):  
V Elias ◽  
R B Mann ◽  
D.G.C. McKeon ◽  
T G Steele
Keyword(s):  
Field Theory ◽  
Scalar Field ◽  
Standard Model ◽  
Symmetry Breaking ◽  
Top Quark ◽  
Higgs Mass ◽  
Electroweak Symmetry Breaking ◽  
Electroweak Symmetry ◽  
The Standard Model ◽  
Leading Logarithm

The top-quark Yukawa coupling is too large to permit radiative electroweak symmetry breaking to occur, to leading-logarithm order, for small values of y — the Higgs self-coupling. However, a large y solution leading to a viable Higgs mass of approximately 220 GeV does exist, and differs from conventional symmetry breaking by an approximately five-fold enhancement of the Higgs self-coupling. This scenario for radiative symmetry breaking is reviewed, and the order-by-order perturbative stability of this scenario is studied within the scalar-field theory projection of the Standard Model in which the Higgs self-coupling y represents the dominant Standard-Model coupling.PACS Nos.: 11.30.Qc, 11.10.Hi, 11.15.Tk, 12.15.Lk

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