scholarly journals Super-Weak Force and Neutrino Masses

Symmetry ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 107 ◽  
Author(s):  
Zoltán Trócsányi
Keyword(s):  
Abelian Group ◽  
Scalar Field ◽  
New Right ◽  
Neutrino Masses ◽  
Anomaly Cancellation ◽  
Weak Force ◽  
Left Handed ◽  
Free Extension ◽  
The Standard Model ◽  
Standard Model Gauge Group

We consider an anomaly free extension of the standard model gauge group G SM by an abelian group to G SM ⊗ U ( 1 ) Z . The condition of anomaly cancellation is known to fix the Z-charges of the particles, but two. We fix one remaining charge by allowing for all possible Yukawa interactions of the known left-handed neutrinos and new right-handed ones that obtain their masses through interaction with a new scalar field with spontaneously broken vacuum. We discuss some of the possible consequences of the model.

AN SU(2)L×U(1)L×U(1)R MODEL WITH FINITE DIRAC NEUTRINO MASSES

1993 ◽  
Vol 08 (10) ◽  
pp. 895-902 ◽  
Author(s):  
SUBHASH RAJPOOT
Keyword(s):  
Standard Model ◽  
Discrete Symmetry ◽  
Lepton Number ◽  
Tree Level ◽  
Neutrino Masses ◽  
Charged Scalar ◽  
Dirac Neutrino ◽  
Left Handed ◽  
The Standard Model ◽  
The One

An SU(2)L×U(1)L×U(1)R model of electroweak interactions is presented in which the conventional fermions of the standard model are left-handed doublets under SU(2)L× U(1)L and are right-handed singlets under U(1) R . The triangle anomalies are canceled by adding vector-like singlet fermions. Neutrinos are massless at the tree level due to a discrete symmetry and acquire tiny finite masses at the one-loop level due to the exchange of two charged scalar singlets. The singlet scalars carry two units of lepton number.

scholarly journals MODEL FOR SMALL NEUTRINO MASSES AT THE TeV SCALE

2002 ◽  
Vol 17 (13) ◽  
pp. 771-778 ◽  
Author(s):  
SALAH NASRI ◽  
SHERIF MOUSSA
Keyword(s):  
Standard Model ◽  
Majorana Neutrino ◽  
Lepton Number ◽  
Neutrino Masses ◽  
Mass Generation ◽  
Seesaw Mechanism ◽  
Left Handed ◽  
The Standard Model ◽  
Neutrino Mass Generation ◽  
The One

We propose a model for neutrino mass generation in which no physics beyond a TeV is required. We extend the standard model by adding two charged singlet fields with lepton number two. Dirac neutrino masses mνD ≤ MeV are generated at the one-loop level. Small left-handed Majorana neutrino masses can be generated via the seesaw mechanism with right-handed neutrino masses MR of order TeV scale.

scholarly journals If the weak were strong and the strong were weak

2019 ◽  
Vol 7 (5) ◽  
Author(s):  
Nakarin Lohitsiri ◽  
David Tong
Keyword(s):  
Phase Transition ◽  
Standard Model ◽  
Phase Structure ◽  
Chiral Symmetry Breaking ◽  
Weak Force ◽  
Strong Force ◽  
Left Handed ◽  
Down Quark ◽  
The Standard Model ◽  
Two Parameter

We explore the phase structure of the Standard Model as the relative strengths of the SU(2)SU(2) weak force and SU(3)SU(3) strong force are varied. With a single generation of fermions, the structure of chiral symmetry breaking suggests that there is no phase transition as we interpolate between the SU(3)SU(3)-confining phase and the SU(2)SU(2)-confining phase. Remarkably, the massless left-handed neutrino, familiar in our world, morphs smoothly into a massless right-handed down-quark. With multiple generations, a similar metamorphosis occurs, but now proceeding via a phase transition. In the second half of the paper we introduce a two-parameter extension of the Standard Model, a chiral gauge theory with gauge group U(1)\times Sp(r)\times SU(N)U(1)×Sp(r)×SU(N). We again explore the phase structure of the theory as the relative strengths of the Sp(r)Sp(r) and SU(N)SU(N) gauge couplings vary.

scholarly journals FERMION MASS HIERARCHY IN LIFSHITZ TYPE GAUGE THEORY

2010 ◽  
Vol 25 (19) ◽  
pp. 1613-1623 ◽  
Author(s):  
KUNIO KANETA ◽  
YOSHIHARU KAWAMURA
Keyword(s):  
Gauge Theory ◽  
Scalar Field ◽  
Fermion Mass ◽  
Mass Hierarchy ◽  
Left Handed ◽  
Fermion Masses ◽  
The Standard Model ◽  
Flavor Mixing ◽  
The Hierarchical Structure ◽  
Associated Operators

We study the origin of fermion mass hierarchy and flavor mixing in a Lifshitz type extension of the standard model including an extra scalar field. We show that the hierarchical structure can originate from renormalizable interactions. In contrast to the ordinary Froggatt–Nielsen mechanism, the higher the dimension of associated operators, the heavier the fermion masses. Tiny masses for left-handed neutrinos are obtained without introducing right-handed neutrinos.

scholarly journals The singly-charged scalar singlet as the origin of neutrino masses

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Tobias Felkl ◽  
Juan Herrero-García ◽  
Michael A. Schmidt
Keyword(s):  
Mass Matrix ◽  
Boson Mass ◽  
Neutrino Masses ◽  
Charged Scalar ◽  
Yukawa Couplings ◽  
Left Handed ◽  
Flavour Violation ◽  
Singly Charged ◽  
Charged Lepton Sector ◽  
Scalar Singlet

Abstract We consider the generation of neutrino masses via a singly-charged scalar singlet. Under general assumptions we identify two distinct structures for the neutrino mass matrix. This yields a constraint for the antisymmetric Yukawa coupling of the singly-charged scalar singlet to two left-handed lepton doublets, irrespective of how the breaking of lepton-number conservation is achieved. The constraint disfavours large hierarchies among the Yukawa couplings. We study the implications for the phenomenology of lepton-flavour universality, measurements of the W-boson mass, flavour violation in the charged-lepton sector and decays of the singly-charged scalar singlet. We also discuss the parameter space that can address the Cabibbo Angle Anomaly.

scholarly journals A note on gauge anomaly cancellation in effective field theories

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Ferruccio Feruglio
Keyword(s):  
Effective Field Theories ◽  
Effective Field ◽  
Field Theories ◽  
Anomaly Cancellation ◽  
Charge Assignment ◽  
The Standard Model ◽  
Renormalizable Theory ◽  
Complete Set ◽  
Gauge Anomalies ◽  
Gauge Anomaly

Abstract The conditions for the absence of gauge anomalies in effective field theories (EFT) are rivisited. General results from the cohomology of the BRST operator do not prevent potential anomalies arising from the non-renormalizable sector, when the gauge group is not semi-simple, like in the Standard Model EFT (SMEFT). By considering a simple explicit model that mimics the SMEFT properties, we compute the anomaly in the regularized theory, including a complete set of dimension six operators. We show that the dependence of the anomaly on the non-renormalizable part can be removed by adding a local counterterm to the theory. As a result the condition for gauge anomaly cancellation is completely controlled by the charge assignment of the fermion sector, as in the renormalizable theory.

scholarly journals Lowering the scale of Pati-Salam breaking through seesaw mixing

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Matthew J. Dolan ◽  
Tomasz P. Dutka ◽  
Raymond R. Volkas
Keyword(s):  
Degrees Of Freedom ◽  
Tree Level ◽  
Charged Current ◽  
Meson Decay ◽  
Neutrino Masses ◽  
Down Quark ◽  
The Standard Model ◽  
Decay Widths ◽  
Left And Right ◽  
Charged Leptons

Abstract We analyse the experimental limits on the breaking scale of Pati-Salam extensions of the Standard Model. These arise from the experimental limits on rare-meson decay processes mediated at tree-level by the vector leptoquark in the model. This leptoquark ordinarily couples to both left- and right-handed SM fermions and therefore the meson decays do not experience a helicity suppression. We find that the current limits vary from $$ \mathcal{O} $$ O (80–2500) TeV depending on the choice of matrix structure appearing in the relevant three-generational charged-current interactions. We extensively analyse scenarios where additional fermionic degrees of freedom are introduced, transforming as complete Pati-Salam multiplets. These can lower the scales of Pati-Salam breaking through mass-mixing within the charged-lepton and down-quark sectors, leading to a helicity suppression of the meson decay widths which constrain Pati-Salam breaking. We find four multiplets with varying degrees of viability for this purpose: an SU(2)L/R bidoublet, a pair of SU(4) decuplets and either an SU(2)L or SU(2)R triplet all of which contain heavy exotic versions of the SM charged leptons. We find that the Pati-Salam limits can be as low as $$ \mathcal{O} $$ O (5–150) TeV with the addition of these four multiplets. We also identify an interesting possible connection between the smallness of the neutrino masses and a helicity suppression of the Pati-Salam limits for three of the four multiplets.

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 Another SMEFT story: Z′ facing new results on ε′/ε, ∆MK and K → $$ \pi \nu \overline{\nu} $$

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Jason Aebischer ◽  
Andrzej J. Buras ◽  
Jacky Kumar
Keyword(s):  
Renormalization Group ◽  
Mass Difference ◽  
Branching Ratios ◽  
New Physics ◽  
Matrix Elements ◽  
Isospin Breaking ◽  
Left Handed ◽  
The Standard Model ◽  
First Time ◽  
Group Effects

Abstract Recently the RBC-UKQCD lattice QCD collaboration presented new results for the hadronic matrix elements relevant for the ratio ε′/ε in the Standard Model (SM) albeit with significant uncertainties. With the present knowledge of the Wilson coefficients and isospin breaking effects there is still a sizable room left for new physics (NP) contributions to ε′/ε which could both enhance or suppress this ratio to agree with the data. The new SM value for the K0 − $$ {\overline{K}}^0 $$ K ¯ 0 mass difference ∆MK from RBC-UKQCD is on the other hand by 2σ above the data hinting for NP required to suppress ∆MK. Simultaneously the most recent results for K+ → $$ {\pi}^{+}\nu \overline{\nu} $$ π + ν ν ¯ from NA62 and for KL → $$ {\pi}^0\nu \overline{\nu} $$ π 0 ν ν ¯ from KOTO still allow for significant NP contributions. We point out that the suppression of ∆MK by NP requires the presence of new CP-violating phases with interesting implications for K → $$ \pi \nu \overline{\nu} $$ πν ν ¯ , KS → μ+μ− and KL → π0ℓ+ℓ− decays. Considering a Z′-scenario within the SMEFT we analyze the dependence of all these observables on the size of NP still allowed by the data on ε′/ε. The hinted ∆MK anomaly together with the εK constraint implies in the presence of only left-handed (LH) or right-handed (RH) flavour-violating Z′ couplings strict correlation between K+ → $$ {\pi}^{+}\nu \overline{\nu} $$ π + ν ν ¯ and KL → $$ {\pi}^0\nu \overline{\nu} $$ π 0 ν ν ¯ branching ratios so that they are either simultaneously enhanced or suppressed relative to SM predictions. An anticorrelation can only be obtained in the presence of both LH and RH couplings. Interestingly, the NP QCD penguin scenario for ε′/ε is excluded by SMEFT renormalization group effects in εK so that NP effects in ε′/ε are governed by electroweak penguins. We also investigate for the first time whether the presence of a heavy Z′ with flavour violating couplings could generate through top Yukawa renormalization group effects FCNCs mediated by the SM Z-boson. The outcome turns out to be very interesting.

TeV Scale B – L Phenomenology at LHC

2007 ◽  
Vol 22 (31) ◽  
pp. 5889-5908 ◽  
Author(s):  
M. Abbas ◽  
W. Emam ◽  
S. Khalil ◽  
M. Shalaby
Keyword(s):  
Standard Model ◽  
Gauge Boson ◽  
Cross Sections ◽  
Branching Ratios ◽  
Higgs Production ◽  
Neutrino Masses ◽  
Natural Explanation ◽  
The Standard Model ◽  
The Cross

We present the phenomenology of the low scale U(1)B–L extension of the standard model and its implications at LHC. We show that this model provides a natural explanation for the presence of three right-handed neutrinos and can naturally account the observed neutrino masses and mixing. We study the decay and production of the extra gauge boson and the SM singlet scalar (heavy Higgs) predicted in this type of models. We find that the cross sections of the SM-like Higgs production are reduced by ~ 20% – 30%, while its decay branching ratios remain intact. The extra Higgs has relatively small cross sections and the branching ratios of Z′ → l+l− are of order ~ 20% compared to ~ 3% of the SM results.

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