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 The ScotoSinglet Model: a scalar singlet extension of the Scotogenic Model

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Ankit Beniwal ◽  
Juan Herrero-García ◽  
Nicholas Leerdam ◽  
Martin White ◽  
Anthony G. Williams
Keyword(s):  
Parameter Space ◽  
Direct Detection ◽  
Neutrino Masses ◽  
Minimal Models ◽  
Flavour Violation ◽  
The One ◽  
Relic Abundance ◽  
Electroweak Precision ◽  
Scalar Singlet ◽  
Lepton Flavour

Abstract The Scotogenic Model is one of the most minimal models to account for both neutrino masses and dark matter (DM). In this model, neutrino masses are generated at the one-loop level, and in principle, both the lightest fermion singlet and the lightest neutral component of the scalar doublet can be viable DM candidates. However, the correct DM relic abundance can only be obtained in somewhat small regions of the parameter space, as there are strong constraints stemming from lepton flavour violation, neutrino masses, electroweak precision tests and direct detection. For the case of scalar DM, a sufficiently large lepton-number-violating coupling is required, whereas for fermionic DM, coannihilations are typically necessary. In this work, we study how the new scalar singlet modifies the phenomenology of the Scotogenic Model, particularly in the case of scalar DM. We find that the new singlet modifies both the phenomenology of neutrino masses and scalar DM, and opens up a large portion of the parameter space of the original model.

NEUTRINO MASSES AND TeV SCALE RESONANT LEPTOGENESIS FROM SUPERSYMMETRY BREAKING

2006 ◽  
Vol 21 (21) ◽  
pp. 1629-1646 ◽  
Author(s):  
STEPHEN M. WEST
Keyword(s):  
Supersymmetry Breaking ◽  
Mass Matrix ◽  
Mass Splitting ◽  
Light Neutrino ◽  
Tree Level ◽  
Neutrino Masses ◽  
Yukawa Couplings ◽  
Neutrino Sector ◽  
The One ◽  
The Right

We review a class of supersymmetric models in which the light neutrino masses result from higher-dimensional supersymmetry-breaking terms in the MSSM super- and Kähler-potentials. The mechanism used in these models is closely related to the Giudice–Masiero mechanism for the MSSM μ parameter and leads to TeV-scale right-handed neutrino and sneutrino states. In these models, the dominant contribution to the light neutrino (Majorana) mass matrix is a one-loop term with a sub-dominant tree-level "seesaw" contribution. It is also shown that it is possible to construct a natural model of TeV-scale leptogenesis via the resonant behavior of the one-loop self-energy contribution to the right-handed neutrino (Ni) decay. This model addresses the primary problems of previous phenomenological studies of low-energy leptogenesis: a rational for TeV-scale right-handed neutrinos with small Yukawa couplings; the origin of the tiny, but non-zero mass splitting required between at least two Ni masses; and the necessary non-trivial breaking of flavor symmetries in the right-handed neutrino sector.

scholarly journals Contribution of right-handed neutrinos and standard fermions to W± and Z masses

2015 ◽  
Vol 30 (19) ◽  
pp. 1550094 ◽  
Author(s):  
Petr Beneš
Keyword(s):  
Gauge Boson ◽  
Decay Constant ◽  
Mass Matrix ◽  
Z Bosons ◽  
Boson Mass ◽  
Pion Decay ◽  
Pion Decay Constant ◽  
Left Handed ◽  
Gauge Boson Mass ◽  
The Masses

We present expressions of the Pagels–Stokar (PS) type for the masses of the [Formula: see text] and Z bosons in terms of the quark and lepton self-energies. By introducing a genuine new term in the gauge boson-fermion–anti-fermion vertex we manage to accomplish three main achievements: First, we show that the similar results existing in literature lead, in general, to a nonsymmetric gauge boson mass matrix and we fix this flaw. Second, we consider the case of any number of fermion generations with general mixing. Third, we include in our analysis also an arbitrary number of right-handed neutrinos, together with the left-handed and right-handed neutrino Majorana masses (self-energies). On top of that, we give also a correction to the original PS formula for the pion decay constant in QCD.

scholarly journals Neutrino masses in an $$SU(4)\otimes U(1)$$-electroweak model with a scalar decuplet

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
N. Anh Ky ◽  
N. T. Hong Van ◽  
D. Nguyen Dinh ◽  
P. Quang Van
Keyword(s):  
Symmetry Breaking ◽  
Neutrino Mass ◽  
Particle Physics ◽  
Mass Matrix ◽  
Neutrino Masses ◽  
Coupling Coefficients ◽  
Mass Model ◽  
Yukawa Couplings ◽  
Distribution Shape ◽  
Independent Distribution

Abstract A neutrino mass model is suggested within an $$SU(4)\otimes U(1)$$SU(4)⊗U(1)-electroweak theory. The smallness of neutrino masses can be guaranteed by a seesaw mechanism realized through Yukawa couplings to a scalar SU(4)-decuplet. In this scheme the light active neutrinos are accompanied by heavy neutrinos, which may have masses at different scales, including those within eV–MeV scales investigated quite intensively in both particle physics and astrophysics/cosmology. The flavour neutrinos are superpositions of light neutrinos and a small fraction of heavy neutrinos with the mixing to be determined by the model’s parameters (Yukawa coupling coefficients or symmetry breaking scales). The distribution shape of the Yukawa couplings can be visualized via a model-independent distribution of the neutrino mass matrix elements derived by using the current experimental data. The absolute values of these Yukawa couplings are able to be determined if the symmetry breaking scales are known, and vice versa. With reference to several current and near future experiments, detectable bounds of these heavy neutrinos at different mass scales are discussed and estimated.

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 Unified framework for B-anomalies, muon g − 2 and neutrino masses

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
K. S. Babu ◽  
P. S. Bhupal Dev ◽  
Sudip Jana ◽  
Anil Thapa
Keyword(s):  
Neutrino Masses ◽  
Hadron Colliders ◽  
Unified Framework ◽  
Final State ◽  
Charged Scalar ◽  
Meson Decays ◽  
Yukawa Couplings ◽  
Upper Limits ◽  
Tau Pairs ◽  
Doubly Charged

Abstract We present a model of radiative neutrino masses which also resolves anomalies reported in B-meson decays, $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ and $$ {R}_{K^{\left(\ast \right)}} $$ R K ∗ , as well as in muon g − 2 measurement, ∆aμ. Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars R2 and S3. Fits to neutrino oscillation parameters are obtained satisfying all flavor constraints which also explain the anomalies in $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ , $$ {R}_{K^{\left(\ast \right)}} $$ R K ∗ and ∆aμ within 1 σ. An isospin-3/2 Higgs quadruplet plays a crucial role in generating neutrino masses; we point out that the doubly-charged scalar contained therein can be produced in the decays of the S3 LQ, which enhances its reach to 1.1 (6.2) TeV at $$ \sqrt{s} $$ s = 14 TeV high-luminosity LHC ($$ \sqrt{s} $$ s = 100 TeV FCC-hh). We also present flavor-dependent upper limits on the Yukawa couplings of the LQs to the first two family fermions, arising from non-resonant dilepton (pp → ℓ+ℓ−) processes mediated by t-channel LQ exchange, which for 1 TeV LQ mass, are found to be in the range (0.15 − 0.36). These limits preclude any explanation of $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ through LQ-mediated B-meson decays involving νe or νμ in the final state. We also find that the same Yukawa couplings responsible for the chirally-enhanced contribution to ∆aμ give rise to new contributions to the SM Higgs decays to muon and tau pairs, with the modifications to the corresponding branching ratios being at (2–6)% level, which could be tested at future hadron colliders, such as HL-LHC and FCC-hh.

scholarly journals LARGE SOLAR NEUTRINO MIXING IN AN EXTENDED ZEE MODEL

2002 ◽  
Vol 17 (19) ◽  
pp. 2519-2533 ◽  
Author(s):  
TERUYUKI KITABAYASHI ◽  
MASAYAKI YASUÈ
Keyword(s):  
Solar Neutrino ◽  
Electron Mass ◽  
Neutrino Mixing ◽  
Charged Scalar ◽  
Seesaw Mechanism ◽  
Left Handed ◽  
Mass Terms ◽  
Charged Leptons ◽  
Singly Charged ◽  
Higgs Scalar

The Zee model, which employs the standard Higgs scalar (ϕ) with its duplicate (ϕ ′) and a singly charged scalar (h+), can utilize two global symmetries associated with the conservation of the numbers of ϕ and ϕ′, Nϕ, ϕ′, where Nϕ + Nϕ′ coincides with the hypercharge while Nϕ - Nϕ′ (≡ X) is a new conserved charge, which is identical to Le - Lμ - Lτ for the left-handed leptons. Charged leptons turn out to have e–μ and e–τ mixing masses, which are found to be crucial for the large solar neutrino mixing. In an extended version of the Zee model with an extra triplet Higgs scalar (s), neutrino oscillations are described by three steps: (1) the maximal atmospheric mixing is induced by democratic mass terms supplied by s with X = 2 that can initiate the type II seesaw mechanism for the smallness of these masses; (2) the maximal solar neutrino mixing is triggered by the creation of radiative masses by h+ with X=0; (3) the large solar neutrino mixing is finally induced by a νμ - ντ mixing arising from the rotation of the radiative mass terms as a result of the diagonalization that converts e–μ and e–τ mixing masses into the electron mass.

scholarly journals Searching for lepton flavor universality violation and collider signals from a singly charged scalar singlet

2021 ◽  
Vol 103 (7) ◽  
Author(s):  
Andreas Crivellin ◽  
Fiona Kirk ◽  
Claudio Andrea Manzari ◽  
Luca Panizzi
Keyword(s):  
Charged Scalar ◽  
Lepton Flavor ◽  
Singly Charged ◽  
Scalar Singlet

scholarly journals Neutrino masses, vacuum stability and quantum gravity prediction for the mass of the top quark

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Guillem Domènech ◽  
Mark Goodsell ◽  
Christof Wetterich
Keyword(s):  
Quantum Gravity ◽  
Top Quark ◽  
Quark Mass ◽  
Scalar Potential ◽  
Planck Scale ◽  
Neutrino Masses ◽  
Top Quark Mass ◽  
Vacuum Stability ◽  
Intermediate Scale ◽  
Yukawa Couplings

Abstract A general prediction from asymptotically safe quantum gravity is the approximate vanishing of all quartic scalar couplings at the UV fixed point beyond the Planck scale. A vanishing Higgs doublet quartic coupling near the Planck scale translates into a prediction for the ratio between the mass of the Higgs boson MH and the top quark Mt. If only the standard model particles contribute to the running of couplings below the Planck mass, the observed MH∼ 125 GeV results in the prediction for the top quark mass Mt∼ 171 GeV, in agreement with recent measurements. In this work, we study how the asymptotic safety prediction for the top quark mass is affected by possible physics at an intermediate scale. We investigate the effect of an SU(2) triplet scalar and right-handed neutrinos, needed to explain the tiny mass of left-handed neutrinos. For pure seesaw II, with no or very heavy right handed neutrinos, the top mass can increase to Mt ∼ 172.5 GeV for a triplet mass of M∆ ∼ 108GeV. Right handed neutrino masses at an intermediate scale increase the uncertainty of the predictions of Mt due to unknown Yukawa couplings of the right-handed neutrinos and a cubic interaction in the scalar potential. For an appropriate range of Yukawa couplings there is no longer an issue of vacuum stability.

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