arXiv subjects

Mohamed Amin Loualidi

Publications and source records attributed to Mohamed Amin Loualidi.

9 recordsLinked to original sources

arXiv2026

Radiative Neutrino Mass in a Nonholomorphic $T'$ Modular Invariant Model

The T4-2-i topology provides a one-loop realization of Majorana neutrino mass and may be viewed as a radiative extension of the type-II seesaw, with a scalar triplet, two inert scalar doublets, and singlet fermions propagating in the loop. A central difficulty in realizing this topology lies in the simultaneous presence of tree-level type-I and type-II seesaw contributions arising from the same particle content. In addition, the stability of the dark matter candidate typically requires the introduction of an ad hoc discrete symmetry. In this work, we revisit the T4-2-i topology within a nonholomorphic modular invariant framework based on the double cover group $T'$. The presence of both even and odd weight polyharmonic Maaß forms considerably enlarges the space of allowed modular structures. An exact $Z_2$ parity inherited from the $T'$ modular symmetry stabilizes the lightest odd state for arbitrary values of $τ$, whereas the vicinity of $τ=i$ determines the flavor textures. The modular assignments exclude the tree-level type-I operator and determine the flavor structure, while lepton number conservation in the Yukawa sector excludes the tree-level type-II coupling. The modular invariant Majorana mass matrix provides the soft $ΔL = 2$ breaking required by the radiative mechanism. We confront the model with neutrino oscillation data, charged lepton flavor violating bounds, electroweak precision observables, the Higgs diphoton signal strength, the observed dark matter relic abundance, the cosmological bound on the sum of neutrino masses, and direct detection limits. Focusing on the fermionic dark matter candidate, in which the lightest odd state is the Majorana fermion $N_1$, we find that both normal and inverted neutrino mass orderings remain viable.

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arXiv2026

Neutrino mass, scalar dark matter, and collider signatures in a radiative doublet-triplet model

We explore a radiative neutrino mass model based on the topology T4-3-i, which is a one-loop completion of the Weinberg operator. We focus on its T4-3-i-C1 realization, containing an inert scalar doublet, a real scalar triplet, a Majorana fermion triplet, and a Dirac singlet fermion. An exact $Z_2$ symmetry forbids the tree-level type-III term and stabilizes the lightest $Z_2$-odd particle, leaving the one-loop topology as the leading source of neutrino mass. The model accomodate a neutral {\it CP}-even scalar dark matter candidate and predicts a rank two neutrino mass matrix, and thus one neutrino is massless. A combined analysis incorporating theoretical and experimental constraints reveals viable solutions to both neutrino mass orderings, with the inverted ordering predicting larger values of $m_{ββ}$, $m_β$, and $\sum_i m_i$, thereby enhancing its testability through future beta-decay, neutrinoless double beta decay, and cosmological probes. Within the same viable parameter region, the observed dark matter relic abundance is accounted for by annihilation and coannihilation processes, while the electroweak triplet sector gives rise to prompt, displaced, or long-lived particle signatures, offering complementary collider probes to dark matter and low-energy searches.

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arXiv2026

A Novel One-loop Model for Majorana Neutrino Mass and Dark Matter

We present the first complete field-theoretic realization of the finite one-loop T4-3-i topology for Majorana neutrino mass. Here, T4-3-i denotes a one-loop realization of the Weinberg operator in which a fermion links the two external lepton--Higgs pairs. If this fermion is a Majorana singlet or triplet, the same interactions generate a tree-level type-I or type-III seesaw contribution, respectively, so that the loop is not the leading source of neutrino mass. This lower-order contribution is removed by taking the mediator to be a Dirac fermion $N$, placing lepton-number violation in a separate Majorana fermion $ψ$ inside the loop, and imposing an exact $Z_2$ symmetry that keeps the new scalars inert and stabilizes the lightest odd state. We classify the allowed electroweak charge assignments and study the minimal singlet-doublet realization, denoted T4-3-i-B1, which contains one Dirac fermion, one Majorana fermion, an inert scalar doublet, and an inert scalar singlet. The resulting rank-two neutrino mass matrix predicts one massless neutrino. We confront both normal and inverted neutrino-mass orderings with neutrino-oscillation and cosmological data, charged-lepton flavor violation, including $μ-e$ conversion, electroweak precision observables, $h\toγγ$, theoretical consistency conditions, the relic abundance, and direct-detection limits. Both fermionic and scalar dark matter are viable. The fermionic candidate has only a loop-induced Higgs coupling and consequently a strongly suppressed spin-independent scattering rate, whereas the scalar candidate couples through a tree-level Higgs portal and can lie above the neutrino floor while remaining compatible with current limits. In both cases, coannihilation with inert scalars is essential for reproducing the observed relic abundance.

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arXiv2026

Radiative neutrino mass generation and dark matter through vectorlike leptons

This study presents a radiative three-loop model for neutrino mass generation, employing an asymmetric Yukawa coupling between two new scalar $SU(2)_L$ doublets and vectorlike lepton doublets. Dark matter candidates arise from one of the scalar doublets and contribute to neutrino mass generation through the mass splitting between its neutral components. The singly charged scalars are also essential for neutrino mass, with the charged states of the two doublets mixing with one another. A single generation of vectorlike leptons yields two nonzero neutrino masses as a consequence of the asymmetric Yukawa combinations entering the neutrino mass matrix. The model is tested against dark matter phenomenology, neutrino mass and mixing data, and the charged lepton flavor-violating process $μ\rightarrow e γ$, showing compatibility with current bounds and leading to experimentally accessible predictions.

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arXiv2025

Boosting Sensitivity to $HH\to b\bar{b} γγ$ with Graph Neural Networks and XGBoost

In this paper, we explore the use of advanced machine learning (ML) techniques to enhance the sensitivity of double Higgs boson searches in the $ HH \to b\bar{b}γγ$ decay channel at $\sqrt{s} = $ 13.6 TeV. Two ML models are implemented and compared: a tree-based classifier using XGBoost, and a geometrical-based graph neural network classifier (GNN). We show that the geometrical model outperform the traditional XGBoost classifier improving the expected 95\% CL upper limit on the double Higgs boson production cross-section by 28\%. Our results are compared to the latest ATLAS experiment results, showing significant improvement of both upper limit and Higgs boson self-coupling ($κ_λ$) constraints.

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arXiv2025

Nonholomorphic $A_4$ modular invariance for fermion masses and mixing in SU(5) GUT

Addressing the fermion flavor structures using modular invariance is a challenging task in the framework of quark-lepton unification. Building on recent applications of modular symmetry in non-supersymmetric models, we propose the first renormalizable $SU(5)$ grand unified theory incorporating level 3 nonholomorphic modular symmetry, $Γ_3 \simeq A_4$. This framework constrains Yukawa couplings to polyharmonic Maaß forms, significantly reducing the number of free parameters while enhancing the predictive power of the models. We present a comprehensive analysis of fermion masses and mixing while tackling key GUT queries such as gauge coupling unification and proton decay. Beyond the minimal $SU(5)$ framework, the Higgs sector incorporates the $45_H$ dimensional Higgs field crucial in differentiating the masses of down quarks and charged leptons, and the fermion sector is extended with three right-handed neutrinos enabling neutrino masses via the type-I seesaw mechanism. We analyze two benchmark models with distinct modular weight and $A_4$ charge assignments. The predicted effective Majorana mass $m_{ββ}$ values align with current neutrinoless double-beta decay experiments, and the effective neutrino mass $m_β$ is within the reach of future beta decay searches. The predicted sum of neutrino masses, $\sum m_i$, satisfies the upper bound set by recent cosmological observations. The gauge coupling unification is achieved through a light scalar triplet $ϕ_3 \sim (3,3,-1/3)$ and a scalar octet $ϕ_5 \sim (8,2,1/2)$ belonging to the $45_H$ Higgs, while proton decay constraints require a highly suppressed Yukawa couplings.

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arXiv2025

Fermion Masses and Mixing in Pati-Salam Unification with $S_3$ Modular Symmetry

Modular invariance has recently paved new promising directions in flavor model building. Motivated by this development, we present in this work the first implementation of the $S_3$ modular symmetry within the Pati-Salam unification framework, addressing the flavor structure of quarks and leptons. Assigning left- and right-handed matter fields as $S_3$ doublets or singlets, we propose three benchmark models that achieve compelling fits to sixteen observables including charged fermion mass ratios and flavor mixing parameters. Light neutrino masses arise via the type-I seesaw mechanism, and neutrino oscillation parameters are explored in light of the latest NuFIT-6.0 results. All models favor a normal neutrino mass ordering, with the atmospheric mixing angle lie in the lower octant. For models I and III, the effective Majorana mass $m_{ββ}$ is within the reach of upcoming neutrinoless double-beta decay experiments, while it is too small to be detected in model II. Predicted leptonic CP-violating phases, the sum of active neutrino masses, and Majorana phases span wide but distinctive ranges, enabling future experiments to test and differentiate the proposed models.

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arXiv2024

Domain Walls in the $A_4$ Flavored NMSSM

In this work, we study the phenomenology of neutrinos and the formation of cosmic domain walls in the NMSSM extended by an $A_4 \times Z_3$ flavor symmetry. Neutrino masses result from the type I seesaw mechanism using only two flavon fields and the NMSSM singlet $\mathcal{S}$ while their mixing is of Trimaximal mixing form. We perform our phenomenological study in the normal mass hierarchy where we find that observables like $m_{ββ}$, $m_β$, and $\sum_i m_i$ can be tested by future experiments. Due to the difference between the $A_4$ subgroups that undergo spontaneous breaking in both the charged lepton and neutrino sectors, the resulting domain walls in each sector exhibit distinct structures. We delve into the details of the breaking patterns within these two sectors, and we introduce a nuanced geometric representation for them. To tackle the domain wall problem, we explore a well-established method involving the explicit breaking of the flavor symmetry. This is achieved through the introduction of Planck-suppressed operators induced by supergravity.

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arXiv2023

Cosmological domain walls from the breaking of $\mathbf{S_4}$ flavor symmetry

In this work, we delve into the often-overlooked cosmological implications of spontaneous breaking of non-Abelian discrete groups, specifically focusing on the formation of domain walls in the case of $S_{4}$ flavor symmetry. In particular, we investigate three interesting breaking patterns of the $S_4$ group and study the structure of the domain walls in the broken phase for three possible residual symmetries. The presentation of domain walls in the case of multiple vacua is usually complicated, which therefore implies that most of the analyzes only approximate their presentation. Here, we propose a subtle way to represent the $S_{4}$ domain wall networks by presenting the vacua in each breaking pattern as vectors with their components corresponding to their coordinates in the flavon space. Then, through the properties of the obtained vectors, we find that the domain wall networks can be represented by Platonic or Archimedean solids where the vertices represent the degenerate vacua while the edges correspond to the domain walls that separate them. As an illustration, we propose a type-II seesaw model that is based on the $S_{4}$ flavor symmetry, and study its phenomenological implications on the neutrino sector. To solve the domain wall problem within this toy model, we consider an approach based on high-dimensional effective operators induced by gravity that explicitly break the structure of the induced vacua favoring one vacuum over the others.

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