scholarly journals NEW BOUNDS ON THE STRING SCALE FROM FLAVOR PHYSICS

2004 ◽  
Vol 19 (07) ◽  
pp. 497-509 ◽  
Author(s):  
J. SANTIAGO
Keyword(s):  
Lower Bounds ◽  
Flavor Physics ◽  
Scale Up ◽  
Quantum Corrections ◽  
Tree Level ◽  
Mixing Angles ◽  
Realistic Theory ◽  
Flavor Changing ◽  
Fermion Masses ◽  
Supersymmetric Models

We review the very stringent lower bounds on the string scale that arise from flavor considerations in models with intersecting branes. Despite the absence of a realistic flavor structure at tree level, flavor changing interactions induce a non-trivial pattern of fermion masses and mixing angles when quantum corrections are taken into account. The resulting realistic theory of flavor allows us to constrain, in an unambiguous way, the string scale up to levels difficult to reconcile non-supersymmetric models.

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.

scholarly journals Quantum corrections to slow-roll inflation: scalar and tensor modes

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Jens O. Andersen ◽  
Magdalena Eriksson ◽  
Anders Tranberg
Keyword(s):  
Scalar Field ◽  
Quantum Corrections ◽  
Tree Level ◽  
Field Equations ◽  
Slow Roll ◽  
Scalar Field Equations ◽  
Slow Rolling ◽  
Different Sources ◽  
Suitable Potential ◽  
Quadratic Order

Abstract Inflation is often described through the dynamics of a scalar field, slow-rolling in a suitable potential. Ultimately, this inflaton must be identified with the expectation value of a quantum field, evolving in a quantum effective potential. The shape of this potential is determined by the underlying tree-level potential, dressed by quantum corrections from the scalar field itself and the metric perturbations. Following [1], we compute the effective scalar field equations and the corrected Friedmann equations to quadratic order in both scalar field, scalar metric and tensor perturbations. We identify the quantum corrections from different sources at leading order in slow-roll, and estimate their magnitude in benchmark models of inflation. We comment on the implications of non-minimal coupling to gravity in this context.

scholarly journals SCALAR DARK MATTER EFFECTS IN HIGGS AND TOP QUARK DECAYS

2007 ◽  
Vol 22 (25n28) ◽  
pp. 2121-2129 ◽  
Author(s):  
XIAO-GANG HE ◽  
HO-CHIN TSAI ◽  
TONG LI ◽  
XUE-QIAN LI
Keyword(s):  
Dark Matter ◽  
Top Quark ◽  
Neutral Current ◽  
Higgs Doublet ◽  
Tree Level ◽  
Flavor Changing ◽  
Higgs Decay ◽  
Dark Matter Relic Density ◽  
Flavor Changing Neutral Current ◽  
Two Higgs Doublet Model

We study possible observational effects of scalar dark matter, the darkon D, in Higgs h and top quark t decay processes, h → DD and t → cDD in the minimal Standard Model (SM) and its two Higgs doublet model (THDM) extension supplemented with a SM singlet darkon scalar field D. We find that the darkon D can have a mass in the range of sub-GeV to several tens of GeV, interesting for LHC and ILC colliders, to produce the required dark matter relic density. In the SM with a darkon, t → cDD only occurs at loop level giving a very small rate, while the rate for Higgs decay h → DD can be large. In THDM III with a darkon, where tree level flavor changing neutral current (FCNC) interaction exists, a sizable rate for t → cDD is also possible.

Fermion masses and mixings in a 3-3-1 model withQ4symmetry

2019 ◽  
Vol 34 (25) ◽  
pp. 1950198
Author(s):  
V. V. Vien ◽  
D. P. Khoi
Keyword(s):  
Neutrino Mass ◽  
Mass Parameter ◽  
Majorana Neutrino ◽  
Tree Level ◽  
Type I ◽  
Inverted Hierarchy ◽  
Quark Masses ◽  
Fermion Masses ◽  
Majorana Neutrino Mass ◽  
Good Agreement

We construct a renormalizable [Formula: see text] model with [Formula: see text] symmetry accommodating the observed pattern of fermion masses and mixings with Dirac CP violation phase. The smallness of the active neutrino masses arises from a combination of type I and type II seesaw mechanisms. Both normal and inverted neutrino mass ordering are viable in our model in which the obtained physical observables of the lepton sector are well consistent with the global fit of neutrino oscillation data [P. F. de Salas et al., Phys. Lett. B 782, 633 (2018)] while the CKM matrix is unity at tree level and the quark masses are in good agreement with the experimental data [Particle Data Group (M. Tanabashi et al.), Phys. Rev. D 98, 030001 (2018)]. Furthermore, the model also predicts an effective Majorana neutrino mass parameter of [Formula: see text] eV for normal hierarchy and [Formula: see text] for inverted hierarchy which are consistent with the constraints given in [P. F. de Salas et al., Phys. Lett. B 782, 633 (2018)].

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.

scholarly journals CP SYMMETRY AND FERMION MASSES IN O(10) GRAND UNIFICATION MODELS

1996 ◽  
Vol 11 (34) ◽  
pp. 2703-2713 ◽  
Author(s):  
DAN-DI WU ◽  
YUE-LIANG WU
Keyword(s):  
Coupling Constants ◽  
Grand Unification ◽  
Global Symmetry ◽  
Mass Relation ◽  
Flavor Changing ◽  
Fermion Masses ◽  
Physical Representation ◽  
Cp Symmetry ◽  
Yukawa Sector ◽  
O 10

O(10) grand unification models which do not necessarily have an extra global symmetry are discussed, taking the model with one 10-plet in the Yukawa sector as an example. A strong correlation between mass ratios and CP is found. The mass relation mt/mb=vu/vd is recovered when GW=0; and another special relation mt/mb=GE/GW appears when vd=0, where GE,W are Yukawa coupling constants and vu,d are vevs. To facilitate this discussion, a set of O(10) γ-matrices is offered based on a physical representation of the spinors and that of the vector of the SO(10) group. Flavor changing neutral currents in such models are also discussed.

Nonabelian family symmetry and the origin of fermion masses and mixing angles

1986 ◽  
Vol 179 (1-2) ◽  
pp. 95-102 ◽  
Author(s):  
Mark Soldate ◽  
M.Hall Reno ◽  
Christopher T. Hill
Keyword(s):  
Family Symmetry ◽  
Mixing Angles ◽  
Fermion Masses

Neutrino masses and mixing angles in a predictive theory of fermion masses

1993 ◽  
Vol 47 (9) ◽  
pp. R3697-R3701 ◽  
Author(s):  
Savas Dimopoulos ◽  
Lawrence J. Hall ◽  
Stuart Raby
Keyword(s):  
Neutrino Masses ◽  
Mixing Angles ◽  
Fermion Masses ◽  
Predictive Theory
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