arXiv subjects

Duong Van Loi

Publications and source records attributed to Duong Van Loi.

At least 19 recordsLinked to original sources

arXiv2026

Generation-separated hypercharges and dark charges: origin of flavor, neutrino masses, and dark matter

We study a framework with generation-separated hypercharges and dark charges. After the extended hypercharge symmetry $U(1)_{Y1}\otimes U(1)_{Y2}\otimes U(1)_{Y3}$ is spontaneously broken to the Standard Model $U(1)_Y$, hierarchical masses of charged fermions and small quark mixing can arise from higher-dimensional operators involving hyperon fields. Several realizations with different hyperon sectors are presented to illustrate possible flavor structures. Focusing on the realization with four hyperons, we examine neutrino mass generation through either a seesaw or a scotoseesaw mechanism, which can accommodate tiny neutrino masses and large neutrino mixing. The breaking of the dark gauge symmetry $U(1)_D$ leaves a residual $\mathbb{Z}_2$ symmetry that stabilizes dark matter, allowing either fermionic or scalar candidates with viable TeV-scale parameter regions consistent with the observed dark matter relic abundance and current direct detection constraints.

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arXiv2026

Constraints from the SM-like Higgs boson in a flavor-dependent $U(1)$ extension of the Standard Model

This work presents a phenomenological study of the Standard Model-like Higgs boson $H$ in a flavor-dependent $U(1)_X$ extension of the Standard Model, where the $X$ charge is assigned according to fermion flavors. In particular, we analyze the interactions of $H$ with Standard Model particles as well as with new charged scalar bosons. In addition, the parameter $\ka_{\ga}$, which characterizes the $H\to \ga\ga$ decay at the one-loop level, is investigated. The results show that the model predicts $\ka_{\ga}$ values consistent with the ATLAS and CMS constraints at the $1σ$ level, while satisfying several bounds derived from flavor, collider and dark matter studies.

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arXiv2026

Probing muon anomaly and lepton flavor violation with scalar leptoquarks in the 331LHN model

We extend the $SU(3)_C \times SU(3)_L \times U(1)_X$ model with neutral leptons (331LHN) by introducing scalar leptoquarks. We determine the particle content of the leptoquark multiplets and their Yukawa interactions with fermions. We find that a singlet leptoquark can fully account for the $4.2σ$ discrepancy in the muon anomalous magnetic moment $Δa_μ^{2021}$. The corresponding leptoquark mass is constrained to be $m_S \gtrsim 1.8$~TeV, consistent with current LHC bounds. We further consider the updated $Δa_μ^{2025}$ based on recent lattice QCD results, which strengthen the lower bound to $m_S \gtrsim 6$~TeV. Combining $Δa_μ$ with low-energy leptonic observables, including charged lepton flavor violation and the $μ$--$e$ conversion rate, we constrain the viable parameter space. The allowed leptoquark Yukawa couplings exhibit a normal hierarchical pattern under all constraints. We also investigate the collider phenomenology of the singlet leptoquark, showing that its QCD-driven pair production leads to suppressed signal rates at the LHC for multi-TeV masses, while future hadron colliders can significantly extend the discovery reach.

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arXiv2026

Two-component dark matter from a flavor-dependent $U(1)$ gauge extension

We revisit the dark matter phenomenology of a flavor-dependent $U(1)_X$ gauge extension of the Standard Model, where anomaly cancellation predicts the existence of exactly three fermion generations and requires the presence of three right-handed neutrinos. In Ref.~\cite{VanLoi:2023utt}, a strong hierarchy between the vacuum expectation values of two singlet scalars, $\La_2 \gg \La_1$, renders all $\mathbb{Z}_2$-odd scalar states heavy, resulting in a two-component dark matter scenario composed exclusively of fermions. In the present work, we relax this simplifying assumption and consider a more general mass spectrum. In particular, scalar mixing can naturally lead to a situation in which the lightest $\mathbb{Z}_2$-odd particle is a scalar rather than a fermion. As a consequence, the model admits a qualitatively new realization of two-component dark matter consisting of one fermionic and one scalar component, in addition to the purely fermionic scenario studied previously. We perform a dedicated phenomenological analysis of these two-component dark matter realizations, focusing on the coupled thermal freeze-out dynamics and the resulting relic abundance. Constraints from the observed relic density and current direct-detection limits are taken into account, and viable regions of parameter space are identified.

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arXiv2026

Physical implications of a double right-handed gauge symmetry

Guided by the flipping principle, we propose a novel extension of the Standard Model based on a double right-handed $U(1)$ gauge symmetry. In this framework, all left-handed fermions are neutral, while right-handed fermions of the third generation carry charges distinct from those of the first two generations. This structure naturally explains the observed Standard Model fermion mass hierarchy: the heavy masses of the third generation are generated at tree level, while the lighter masses of the first and second generations arise radiatively at the one-loop level. For the active neutrino sector, the tiny masses are generated through a combination of tree-level and two-loop seesaw mechanisms. Crucially, this approach successfully reproduces the observed neutrino mass hierarchy, with the atmospheric mass-squared difference generated at tree level and the solar neutrino mass squared difference emerging at the two-loop level. These hierarchical patterns stem from the interplay between gauge invariance and a residual parity symmetry that survives the spontaneous breaking of the extended gauge group. The same residual symmetry stabilizes a viable scalar singlet dark matter candidate, which we show can reproduce the observed relic abundance while remaining consistent with current direct detection bounds. After addressing constraints from electroweak precision tests and flavor-changing neutral currents, we explore the discovery prospects for the new neutral bosons at existing and future colliders, including the LEP, LHC, and a future ILC.

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arXiv2025

Lepton Flavor Physics in the flipped 3-3-1-1 Model: Non-Universality and Violation

We investigate the flavor violation (FV) of Z decays to leptons at tree level and flavor conserving Z decays to leptons in the frame work of the flipped $ SU(3)_C\otimes SU(3)_L \otimes U(1)_X\otimes U(1)_N$,(F3311) model. In addition, we analyze the processes $l_i\rightarrow l_j γ$ and the leptonic three-body decay. Using the experimental bounds on these decays we set the constraint on $\sin ϕ$ which represents the mixing between Z-Z' boson. The most stringent limits arises from $μ\rightarrow e γ$ decay where $\sin ϕ\sim \mathcal{ O}(10^{-3})$. The leptonic three-body decay set lower bound on the mass of the new neural gauge boson $m_{Z'} \geq 3.2TeV$. Using the LUX-ZEPLIN (LZ) experiment data we set bounds to the mass of the dark matter candidates. Subsequently, we investigate the lepton non-universality in B decays within the $F3311$ model by calculating the generic one-loop contribution to the process $u_i\rightarrow d_j e_b \barν_a$ in the unitary gauge as well as numerical evaluating the branching ratio $R_D, R_{D^{(*)}},R(X_c)$. We demonstrate that the $F3311$ model can address the $3.3 σ$ discrepancies between Standard Model and experimental data. To reaffirm our results, we also analyze the $d \to u$ transitions and $s\to u$ transitions. These two transitions also give consistent result with experiment data. Combine all experiment dat a we obtain the operating region for the mass of the model specifically $m_E \in [6.5, 9 ]TeV$, $m_Q \in [6,11]TeV$ and the dark matter candidate $m_ξ\in [1.5,2 ]TeV$.

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arXiv2025

Tri-hypercharge versus tri-darkcharge

We propose a minimal, ultraviolet-complete, and renormalizable extension of the Standard Model, in which the three generations of ordinary fermions are distinguished by family-dependent hypercharges, while three right-handed neutrinos are separated by a dark gauge symmetry that is trivial for all Standard Model fields. This setup yields a fully flipped inert doublet model. The model naturally realizes a hybrid scotoseesaw mechanism that accounts for the smallness of neutrino masses and the largeness of lepton mixing. Simultaneously, it explains the stability and relic abundance of dark matter through a residual dark parity and addresses the hierarchies of charged fermion masses and the suppression of quark mixing via higher-dimensional operators involving high-scale scalar singlets and vector-like fermions. We explore the phenomenological implications of the model and derive constraints from electroweak precision tests, collider searches, flavor-changing processes, and observations of dark matter.

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arXiv2025

Dark symmetry implication for right-handed neutrinos

We argue that the long-standing issues of neutrino mass and dark matter can be manifestly solved in a dark gauge symmetry $U(1)_D$ that transforms nontrivially only for three right-handed neutrinos $ν_{1,2,3R}$ -- the counterparts of known left-handed neutrinos. This theory assigns $ν_{1,2,3R}$ dark charge to be $D=0$, $-1$, and $+1$, respectively, in order for anomaly cancelation. Additionally, it imposes an inert Higgs doublet $η$ and two Higgs singlets $ξ,ϕ$ with dark charge $D=+1$, $-1$, and $+2$, respectively. That said, the dark symmetry is broken by $ϕ$ (by two units) down to a dark parity $P_D=(-1)^D$, for which $ν_{2,3R}$ and $η,ξ$ are odd, whereas all other fields are even due to $D=0$. The lightest of these odd fields is stabilized by $P_D$, responsible for dark matter. Neutrino masses are generated by a scotoseesaw scheme, in which the seesaw part is mediated by $ν_{1R}$, while the scotogenic part is mediated by $ν_{2,3R}$, for which the hierarchy of atmospheric and solar neutrino mass splittings is explained.

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arXiv2025

Scoto-seesaw model implied by flavor-dependent Abelian gauge charge

Assuming fundamental fermions possess a new Abelian gauge charge that depends on flavors of both quark and lepton, we obtain a simple extension of the Standard Model, which reveals some new physics insights. The new gauge charge anomaly cancellation not only explains the existence of just three fermion generations as observed but also requires the presence of a unique right-handed neutrino $ν_R$ with a non-zero new gauge charge. Further, the new gauge charge breaking supplies a residual matter parity, under which the fundamental fermions and $ν_R$ are even, whereas a right-handed neutrino $N_R$ without the new charge is odd. Consequently, light neutrino masses in our model are generated from the tree-level type-I seesaw mechanism induced by $ν_R$ and from the one-loop scotogenic contribution accommodated by potential dark matter candidates, $N_R$ and dark scalars, odd under the matter parity. We examine new physics phenomena related to the additional gauge boson, which could be observed at colliders. We analyze the constraints imposed on our model by current experimental limits on neutrino masses, neutral meson oscillations, $B$-meson decays, and charged lepton flavor violating processes. We also investigate the potential dark matter candidates by considering relic density and direct detection.

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arXiv2024

Scotoseesaw model implied by dark right-handed neutrinos

We find a dark gauge symmetry $U(1)_D$ that transforms nontrivially only for three right-handed neutrinos, $ν_{1,2,3R}$. The anomaly cancellation demands that they have a dark charge $D=0,-1,+1$ assigned to $ν_{1,2,3R}$, respectively. The dark charge is broken by two units down to a dark parity, i.e. $U(1)_D\to P_D=(-1)^D$, which stabilizes a dark matter candidate. Interestingly, the model manifestly supplies neutrino masses via joint seesaw and scotogenic mechanisms, called scotoseesaw.

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arXiv2024

Flavor-changing phenomenology in a $U(1)$ model

We investigate a family-nonuniversal Abelian extension of hypercharge, which significantly alters the phenomenological features of the standard model. Anomaly cancellation requires that the third quark family transforms differently from the first two quark families. Additionally, it acquires that three right-handed neutrinos are presented. This model generates naturally small neutrino masses and a $W$-boson mass deviation appropriate to recent measurements. Additionally, the model introduces flavor-changing neutral currents (FCNCs) of quarks coupled to the new gauge boson $Z'$ and new Higgs fields. These FCNCs significantly modify the neutral-meson mixing amplitudes and rare meson decays, which are studied in detail. We also address flavor changing processes in the charged lepton sector.

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arXiv2024

Scotogenic model from an extended electroweak symmetry

We argue that the higher weak isospin $SU(3)_L$ manifestly unifies dark matter and normal matter in its isomultiplets for which dark matter carries a conserved dark charge while normal matter does not. The resultant gauge symmetry is given by $SU(3)_C\otimes SU(3)_L \otimes U(1)_X\otimes U(1)_G$, where the first factor is the color group, while the rest defines a theory of scotoelectroweak in which $X$ and $G$ determine electric charge $Q=T_3-1/\sqrt{3}T_8+X$ and dark charge $D=-2/\sqrt{3}T_8+G$. This setup provides both appropriate scotogenic neutrino masses and dark matter stability as preserved by a residual dark parity $P_D=(-1)^D$. Interpretation of the dark charge is further discussed, given that $SU(3)_L$ is broken at very high energy scale.

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arXiv2024

Questions of flavor physics and neutrino mass from a flipped hypercharge

The flavor structure of quarks and leptons is not yet fully understood, but it hints a more fundamental theory of non-universal generations. We therefore propose a simple extension of the Standard Model by flipping (i.e., enlarging) the hypercharge $U(1)_Y$ to $U(1)_X\otimes U(1)_N$ for which both $X$ and $N$ depend on generations of both quark and lepton. By anomaly cancellation, this extension not only explains the existence of just three fermion generations as observed but also requires the presence of a right-handed neutrino per generation, which motivates seesaw neutrino mass generation. Furthermore, in its minimal version with a scalar doublet and two scalar singlets, the model naturally generates the measured fermion-mixing matrices while it successfully accommodates several flavor anomalies observed in the neutral meson mixings, $B$-meson decays, lepton-flavor-violating processes of charged leptons, as well as satisfying constraints from particle colliders.

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arXiv2023

Flavor-dependent $U(1)$ extension inspired by lepton, baryon and color numbers

There is no reason why the gauge symmetry extension is family universal as in the standard model and the most well-motivated models, e.g. left-right symmetry and grand unification. Hence, we propose a simplest extension of the standard model -- a flavor-dependent $U(1)$ gauge symmetry -- and find the new physics insight. For this aim, the $U(1)$ charge, called $X$, is expressed as $X=x B+y L$ in which $x$ and $y$ are free parameters as functions of flavor index, e.g. for a flavor $i$ they take $x_i$ and $y_i$ respectively, where $B$ and $L$ denote normal baryon and lepton numbers. Imposing a relation involved by the color number $3$, i.e. $-x_{1,2,\cdots,n}=x_{n+1,n+2,\cdots,n+m}=3y_{1,2,\cdots,n+m}\equiv 3z$, for arbitrarily nonzero $z$, we achieve a novel $U(1)$ theory with implied $X$-charge. This theory not only explains the origin of the number of observed fermion families but also offers a possible solution for both neutrino mass and dark matter, which differs from $B-L$ extension. Two typical models based on this idea are examined, yielding interesting results for flavor-changing neutral currents and particle colliders, besides those of neutrino mass and dark matter.

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arXiv2023

Phenomenology of a minimal extension of the standard model with a family-dependent gauge symmetry

We consider a gauge symmetry extension of the standard model given by $SU(3)_C\otimes SU(2)_L\otimes U(1)_X\otimes U(1)_N\otimes Z_2$ with minimal particle content, where $X$ and $N$ are family dependent but determining the hypercharge as $Y=X+N$, while $Z_2$ is an exact discrete symmetry. In our scenario, $X$ (while $N$ is followed by $X-Y$) and $Z_2$ charge assignments are inspired by the number of fermion families and the stability of dark matter, as observed, respectively. We examine the mass spectra of fermions, scalars, and gauge bosons, as well as their interactions, in presence of a kinetic mixing term between $U(1)_{X,N}$ gauge fields. We discuss in detail the phenomenology of the new gauge boson and the right-handed neutrino dark matter stabilized by $Z_2$ conservation. We obtain parameter spaces simultaneously satisfying the recent CDF $W$-boson mass, electroweak precision measurements, particle colliders, as well as dark matter observables, if the kinetic mixing parameter is not necessarily small.

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arXiv2023

Can the Higgs field feel a dark force?

We argue that if an electroweak Higgs field possesses a dark gauge charge responsible for dark matter stability, the $W$-boson mass deviation is properly induced, besides appropriately generated neutrino masses. We examine a simple model in which the usual Higgs doublet plays the role but dark matter candidates are somewhat input by ad hoc. We look for a realistic model that fully realizes such observation, thereby neutrino mass and dark matter are naturally supplied by a dark non-abelian gauge symmetry.

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arXiv2023

Physics implication from higher weak isospin decomposition

The $SU(3)_L\otimes U(1)_X$ symmetry actually studied is directly broken to the electroweak symmetry $SU(2)_L\otimes U(1)_Y$ by a Higgs triplet, predicting a relevant new physics at TeV scale. This work argues, by contrast, that the higher weak isospin $SU(3)_L$ might be broken at a high energy scale, much beyond $1$ TeV, by a Higgs octet to an intermediate symmetry $SU(2)_L\otimes U(1)_{T_8}$ at TeV, before the latter $U(1)_{T_8}$ recombined with $U(1)_X$ defines (i.e., broken to) $U(1)_Y$ by a Higgs singlet. The new physics coupled to $SU(3)_L$ breaking phase is decoupled, whereas what remains is a novel family-nonuniversal abelian model, $U(1)_{T_8}\otimes U(1)_X$, significantly overhauling the standard model as well as yielding consistent results for neutrino mass, dark matter, $W$-mass anomaly, and FCNC, differently from the usual 3-3-1 model.

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arXiv2023

Abelian charge inspired by family number

Quark has an electric charge either $-1/3$ or $2/3$ and a baryon number $1/3$, where the divisions $3$'s match the color number. Although the electric charge and the baryon number have a nature distinct from the color charge, the matching is necessary for the standard model or a relevant $B-L$ extension consistent at quantum level, since the relevant anomaly $[SU(2)_L]^2U(1)_A$ for $A=Y$ or $B-L$ must vanish. If elementary particles have a new $U(1)$ charge differently from $A$, such anomaly is not cancelled for each family. However, if we demand that the anomaly is cancelled over all families, this relates the color number to the family number instead of the electric charge and baryon number, and interestingly the family number guides us to a novel $U(1)$ theory. We will discuss the implication of this theory for neutrino mass, recent $W$-boson mass anomaly, FCNC, and particle colliders.

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