scholarly journals CANONICAL SEESAW MECHANISM IN ELECTROWEAKSU(4)L⊗U(1)YMODELS

2009 ◽  
Vol 24 (32) ◽  
pp. 2589-2600 ◽  
Author(s):  
ADRIAN PALCU
Keyword(s):  
Mass Spectrum ◽  
Standard Model ◽  
Free Parameter ◽  
New Physics ◽  
Seesaw Mechanism ◽  
Gauge Models ◽  
M 10 ◽  
The Standard Model ◽  
Neutrino Mass Spectrum ◽  
Breaking Scale

In this paper we show that the canonical seesaw mechanism can naturally be implemented in a particular class of electroweak SU (4)L⊗ U (1)Ygauge models. The resulting neutrino mass spectrum is determined by just tuning a unique free parameter a within the algebraical method of treating gauge models with high symmetries proposed several years ago by Cotăescu. All the Standard Model phenomenology is preserved, being unaffected by the new physics occurring at a high breaking scale m ~ 1011GeV .

scholarly journals ELECTROWEAKSU(4)L⊗U(1)YMODELS WITHOUT EXOTIC ELECTRIC CHARGES

2009 ◽  
Vol 24 (25n26) ◽  
pp. 4923-4938 ◽  
Author(s):  
ADRIAN PALCU
Keyword(s):  
Mass Spectrum ◽  
Standard Model ◽  
Mass Scale ◽  
Boson Mass ◽  
Gauge Models ◽  
The Standard Model ◽  
The One

For the particular class of SU (4)L⊗ U (1)Yelectroweak models without exotic electric charges, some plausible phenomenological predictions — such as the boson mass spectrum and charges of all the fermions involved therein — are made by using the algebraical approach of the exactly solving method for gauge models with high symmetries. Along with the one-parameter resulting mass scale (to be confirmed at TeV scale in LHC) our approach predicts the exact expressions of the charges (both electric and neutral) in the fermion sector, while all the Standard Model phenomenology is naturally recovered.

scholarly journals NEUTRINO MIXING IN THE μνSSM

2013 ◽  
Vol 28 (24) ◽  
pp. 1350117 ◽  
Author(s):  
HAI-BIN ZHANG ◽  
TAI-FU FENG ◽  
LI-NA KOU ◽  
SHU-MIN ZHAO
Keyword(s):  
Mass Spectrum ◽  
Standard Model ◽  
Tree Level ◽  
Neutrino Masses ◽  
Neutrino Mixing ◽  
Top Down ◽  
Normal Ordering ◽  
Seesaw Mechanism ◽  
Mixing Angle ◽  
Neutrino Mass Spectrum

Recently, several reactor oscillation experiments have successively measured a nonzero value for the neutrino mixing angle θ13, which is greater than five standard deviations. Within framework of the μ from ν Supersymmetric Standard Model (μνSSM), three tiny neutrino masses are generated at the tree level through TeV scale seesaw mechanism. In this work, we analyze the neutrino masses and mixing in the μνSSM with a "top-down" method, assuming neutrino mass spectrum with normal ordering or inverted ordering.

scholarly journals Presymmetry in the Standard Model with adulterated Dirac neutrinos

2015 ◽  
Vol 30 (31) ◽  
pp. 1550160 ◽  
Author(s):  
Ernesto A. Matute
Keyword(s):  
Standard Model ◽  
High Energy ◽  
New Physics ◽  
Boson Mass ◽  
Effective Theory ◽  
Type I ◽  
Electroweak Symmetry ◽  
Seesaw Mechanism ◽  
Left Handed ◽  
The Standard Model

Recently we proposed a model for light Dirac neutrinos in which two right-handed (RH) neutrinos per generation are added to the particles of the Standard Model (SM), implemented with the symmetry of fermionic contents. The ordinary one is decoupled via the high scale type-I seesaw mechanism, while the extra pairs off with its left-handed (LH) partner. The symmetry of lepton and quark contents was merely used as a guideline to the choice of parameters because it is not a proper symmetry. Here we argue that the underlying symmetry to take for this correspondence is presymmetry, the hidden electroweak symmetry of the SM extended with RH neutrinos defined by transformations which exchange lepton and quark bare states with the same electroweak charges and no Majorana mass terms in the underlying Lagrangian. It gives a topological character to fractional charges, relates the number of families to the number of quark colors, and now guarantees the great disparity between the couplings of the two RH neutrinos. Thus, Dirac neutrinos with extremely small masses appear as natural predictions of presymmetry, satisfying the ’t Hooft’s naturalness conditions in the extended seesaw where the extra RH neutrinos serve to adulterate the mass properties in the low scale effective theory, which retains without extensions the gauge and Higgs sectors of the SM. However, the high energy threshold for the seesaw implies new physics to stabilize the quantum corrections to the Higgs boson mass in agreement with the naturalness requirement.

scholarly journals $\bar{B}\rightarrow X_s\gamma$ in the μνSSM

2014 ◽  
Vol 29 (38) ◽  
pp. 1450196 ◽  
Author(s):  
Hai-Bin Zhang ◽  
Guo-Hui Luo ◽  
Tai-Fu Feng ◽  
Shu-Min Zhao ◽  
Tie-Jun Gao ◽  
...  
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Rare Decay ◽  
New Physics ◽  
Majorana Neutrino ◽  
Decay Process ◽  
Neutrino Masses ◽  
Beyond The Standard Model ◽  
Seesaw Mechanism ◽  
The Standard Model

The μνSSM, one of supersymmetric extensions beyond the Standard Model, introduces three singlet right-handed neutrino superfields to solve the μ problem and can generate three tiny Majorana neutrino masses through the seesaw mechanism. In this paper, we investigate the rare decay process [Formula: see text] in the μνSSM, under a minimal flavor violating assumption for the soft breaking terms. Constrained by the SM-like Higgs with mass around 125 GeV, the numerical results show that the new physics can fit the experimental data for [Formula: see text] and further constrain the parameter space.

ELECTRIC CHARGE QUANTIZATION AND VECTOR-LIKE FERMIONS

1990 ◽  
Vol 05 (24) ◽  
pp. 1947-1949 ◽  
Author(s):  
ROBERT FOOT
Keyword(s):  
Standard Model ◽  
Electric Charge ◽  
Life Time ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Simple Method ◽  
Gauge Models ◽  
Flavor Changing ◽  
Charge Quantization ◽  
The Standard Model

In extended gauge models with gauge group G, electric charge quantization is not always an automatic consequence of the consistency of the theory. Exotic fermions which have SU (3) ⊗ SU (2) L ⊗ U (1) invariant mass terms can provide a simple method for preserving the charge quantization feature of the standard model. This procedure is applied to the segregated isospin model.This approach indicates that precision measurements of the τ-lepton life-time and rare flavor-changing neutral processes may provide the first indications of new physics beyond the standard model.

scholarly journals A closer look at observables from exclusive semileptonic B → (π, ρ)ℓνℓ decays

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Aritra Biswas ◽  
Soumitra Nandi
Keyword(s):  
Mass Spectrum ◽  
Standard Model ◽  
Light Cone ◽  
Sum Rules ◽  
Form Factors ◽  
Invariant Mass Spectrum ◽  
New Physics ◽  
Differential Rate ◽  
Decay Modes ◽  
The Standard Model

Abstract This article analyses the available inputs in B → πℓνℓ and B → ρℓνℓ decays which include the measured values of differential rate in different q2-bins (lepton invariant mass spectrum), lattice, and the newly available inputs on the relevant form-factors from the light-cone sum rules (LCSR) approach. We define different fit scenarios, and in each of these scenarios, we predict a few observables in the standard model (SM). For example, $$ R(M)=\frac{\mathcal{B}\left(B\to M{\ell}_i{\nu}_{\ell_i}\right)}{\mathcal{B}\left(B\to M{\ell}_j{\nu}_{\ell_j}\right)},{R}_{\ell_j}^{\ell_i}(M)=\frac{\mathcal{B}\left(B\to {\ell}_i{\nu}_{\ell_i}\right)}{\mathcal{B}\left(B\to M{\ell}_j{\nu}_{\ell_j}\right)} $$ R M = B B → M ℓ i ν ℓ i B B → M ℓ j ν ℓ j , R ℓ j ℓ i M = B B → ℓ i ν ℓ i B B → M ℓ j ν ℓ j with M = π or ρ and ℓi,j = e, μ or τ. We also discuss the new physics (NP) sensitivities of all these observables and obtain bounds on a few NP Wilson coefficients in b → uτντ decays using the available data. We have noted that the data at present allows sizeable NP contributions in this mode. Also, we have predicted a few angular observables relevant to these decay modes.

scholarly journals Standard Model prediction of the Bc lifetime

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Jason Aebischer ◽  
Benjamín Grinstein
Keyword(s):  
Standard Model ◽  
Model Prediction ◽  
Strange Quark ◽  
Standard Model Prediction ◽  
New Physics ◽  
Operator Product ◽  
Special Focus ◽  
Third Order ◽  
Clear Cut ◽  
The Standard Model

Abstract Applying an operator product expansion approach we update the Standard Model prediction of the Bc lifetime from over 20 years ago. The non-perturbative velocity expansion is carried out up to third order in the relative velocity of the heavy quarks. The scheme dependence is studied using three different mass schemes for the $$ \overline{b} $$ b ¯ and c quarks, resulting in three different values consistent with each other and with experiment. Special focus has been laid on renormalon cancellation in the computation. Uncertainties resulting from scale dependence, neglecting the strange quark mass, non-perturbative matrix elements and parametric uncertainties are discussed in detail. The resulting uncertainties are still rather large compared to the experimental ones, and therefore do not allow for clear-cut conclusions concerning New Physics effects in the Bc decay.

scholarly journals Disentangling QCD and new physics in D → πℓ+ℓ−

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Aoife Bharucha ◽  
Diogo Boito ◽  
Cédric Méaux
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
Branching Ratios ◽  
New Physics ◽  
Operator Product ◽  
Beyond The Standard Model ◽  
Spectral Functions ◽  
The Standard Model ◽  
Model Independent ◽  
Weak Annihilation

Abstract In this paper we consider the decay D+ → π+ℓ+ℓ−, addressing in particular the resonance contributions as well as the relatively large contributions from the weak annihilation diagrams. For the weak annihilation diagrams we include known results from QCD factorisation at low q2 and at high q2, adapting the existing calculation for B decays in the Operator Product Expansion. The hadronic resonance contributions are obtained through a dispersion relation, modelling the spectral functions as towers of Regge-like resonances in each channel, as suggested by Shifman, imposing the partonic behaviour in the deep Euclidean. The parameters of the model are extracted using e+e− → (hadrons) and τ → (hadrons) + ντ data as well as the branching ratios for the resonant decays D+ → π+R(R → ℓ+ℓ−), with R = ρ, ω, and ϕ. We perform a thorough error analysis, and present our results for the Standard Model differential branching ratio as a function of q2. Focusing then on the observables FH and AFB, we consider the sensitivity of this channel to effects of physics beyond the Standard Model, both in a model independent way and for the case of leptoquarks.

scholarly journals Indirect $$ \mathcal{CP} $$ probes of the Higgs-top-quark interaction: current LHC constraints and future opportunities

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Henning Bahl ◽  
Philip Bechtle ◽  
Sven Heinemeyer ◽  
Judith Katzy ◽  
Tobias Klingl ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Top Quark ◽  
Decay Channel ◽  
New Physics ◽  
Current Data ◽  
Quark Interaction ◽  
The Standard Model ◽  
Vector Bosons ◽  
Selection Of

Abstract The $$ \mathcal{CP} $$ CP structure of the Higgs boson in its coupling to the particles of the Standard Model is amongst the most important Higgs boson properties which have not yet been constrained with high precision. In this study, all relevant inclusive and differential Higgs boson measurements from the ATLAS and CMS experiments are used to constrain the $$ \mathcal{CP} $$ CP -nature of the top-Yukawa interaction. The model dependence of the constraints is studied by successively allowing for new physics contributions to the couplings of the Higgs boson to massive vector bosons, to photons, and to gluons. In the most general case, we find that the current data still permits a significant $$ \mathcal{CP} $$ CP -odd component in the top-Yukawa coupling. Furthermore, we explore the prospects to further constrain the $$ \mathcal{CP} $$ CP properties of this coupling with future LHC data by determining tH production rates independently from possible accompanying variations of the $$ t\overline{t}H $$ t t ¯ H rate. This is achieved via a careful selection of discriminating observables. At the HL-LHC, we find that evidence for tH production at the Standard Model rate can be achieved in the Higgs to diphoton decay channel alone.

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