arXiv subjects

N. T. K. Ngan

Publications and source records attributed to N. T. K. Ngan.

6 recordsLinked to original sources

arXiv2026

LFV decays in a 3-3-1 model with singlet leptoquarks

Motivated by a recent study of the 3-3-1 model supplemented with a singlet scalar leptoquark, which successfully explains the muon anomalous magnetic moment and the decay $μ\to eγ$ within current experimental constraints, we extend the phenomenological analysis of this framework to include the lepton-flavor-violating decays of the Standard Model-like Higgs and the $Z$ boson. An interesting feature is that the branching ratios of these decays exhibit a nearly linear correlation with the corresponding charged lepton flavor-violating radiative decays, namely $\mathrm{Br}(h,Z\to e_b^\pm e_a^\mp)\propto\mathrm{Br}(e_b\to e_aγ)$. Furthermore, the model exhibits a complementary interplay between the charged-lepton anomalous magnetic moments: parameter regions with $|Δa_μ|\geq10^{-11}$ favor $\mathrm{Br}(h,Z\toτ^\pmμ^\mp)$ reaching their current experimental upper limits while keeping $|Δa_e|$ negligible, whereas regions with $10^{-14}\leq|Δa_e|\leq 8\times10^{-13}$ instead allow $\mathrm{Br}(h,Z\toτ^\pm e^\mp)$ to approach the present experimental sensitivities but simultaneously suppress $|Δa_μ|$ to the level of $\mathcal{O}(10^{-16})$.

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arXiv2024

Decays of Standard Model like Higgs boson $h \rightarrowγγ, Z γ$ in a minimal left-right symmetric model

Two decay channels $h\rightarrow γγ, Zγ$ of the Standard Model-like Higgs in a left-right symmetry model are investigated under recent experimental data. We will show there exist one-loop contributions that affect the $h\rightarrow Zγ$ amplitude, but not the $h\rightarrow γγ$ amplitude. From numerical investigations, we show that the signal strength $μ_{Z γ}$ of the decay $h\rightarrow Zγ$ is still constrained strictly by that of $h\rightarrow γγ$, namely $|Δμ_{γγ}|<38\%$ results in max $|Δμ_{Z γ}|<46\%$. On the other hand, the future experimental sensitivity $|Δμ_{γγ}|=4\%$ still allows $|Δμ_{Z γ}|$ reaches to values larger than the expected sensitivity $|Δμ_{Z γ}|=23\%$.

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arXiv2019

Phenomenology of the simple 3-3-1 model with inert scalars

The simple 3-3-1 model that contains the minimal lepton and minimal scalar contents is detailedly studied. The impact of the inert scalars (i.e., the extra fundamental fields that provide realistic dark matter candidates) on the model is discussed. All the interactions of the model are derived, in which the standard model ones are identified. We constrain the standard model like Higgs particle at the LHC. We search for the new particles including the inert ones, which contribute to the $B_s$-$\bar{B}_s$ mixing, the rare $B_s\rightarrow μ^+μ^-$ decay, the CKM unitarity violation, as well as producing the dilepton, dijet, diboson, diphoton, and monojet final states at the LHC.

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arXiv2017

Probing neutrino and Higgs sectors in $SU(2)_1 \times SU(2)_2 \times U(1)_Y$ model with lepton-flavor non-universality

The neutrino and Higgs sectors in the $\mbox{SU(2)}_1 \times \mbox{SU(2)}_2 \times \mbox{U(1)}_Y $ model with lepton-flavor non-universality are discussed. We show that active neutrinos can get Majorana masses from radiative corrections, after adding only new singly charged Higgs bosons. The mechanism for generation of neutrino masses is the same as in the Zee models. This also gives a hint to solving the dark matter problem based on similar ways discussed recently in many radiative neutrino mass models with dark matter. Except the active neutrinos, the appearance of singly charged Higgs bosons and dark matter does not affect significantly the physical spectrum of all particles in the original model. We indicate this point by investigating the Higgs sector in both cases before and after singly charged scalars are added into it. Many interesting properties of physical Higgs bosons, which were not shown previously, are explored. In particular, the mass matrices of charged and CP-odd Higgs fields are proportional to the coefficient of triple Higgs coupling $μ$. The mass eigenstates and eigenvalues in the CP-even Higgs sector are also presented. All couplings of the SM-like Higgs boson to normal fermions and gauge bosons are different from the SM predictions by a factor $c_h$, which must satisfy the recent global fit of experimental data, namely $0.995<|c_h|<1$. We have analyzed a more general diagonalization of gauge boson mass matrices, then we show that the ratio of the tangents of the $W-W'$ and $Z-Z'$ mixing angles is exactly the cosine of the Weinberg angle, implying that number of parameters is reduced by 1. Signals of new physics from decays of new heavy fermions and Higgs bosons at LHC and constraints of their masses are also discussed.

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arXiv2017

Phenomenology of the SU(3)_C \otimes SU(2)_L \otimes SU(3)_R \otimes U(1)_X gauge model

We study the left-right asymmetric model based on SU(3)_C \otimes SU(2)_L \otimes SU(3)_R \otimes U(1)_X gauge group, which improves the theoretical and phenomenological aspects of the known left-right symmetric model. This new gauge symmetry yields that the fermion generation number is three, and the tree-level flavor-changing neutral currents arise in both gauge and scalar sectors. Also, it can provide the observed neutrino masses as well as dark matter automatically. Further, we investigate the mass spectrum of the gauge and scalar fields. All the gauge interactions of the fermions and scalars are derived. We examine the tree-level contributions of the new neutral vector, Z'_R, and new neutral scalar, H_2, to flavor-violating neutral meson mixings, say K-\bar{K}, B_d-\bar{B}_d, and B_s-\bar{B}_s, which strongly constrain the new physics scale as well as the elements of the right-handed quark mixing matrices. The bounds for the new physics scale are in agreement with those coming from the ρ-parameter as well as the mixing parameters between W, Z bosons and new gauge bosons.

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arXiv2014

Simple 3-3-1 model and implication for dark matter

We propose a new and realistic 3-3-1 model with the minimal lepton and scalar contents, named the simple 3-3-1 model. The scalar sector contains two new heavy Higgs bosons, one neutral H and another singly-charged H^\pm, besides the standard model Higgs boson. There is a mixing between the Z boson and the new neutral gauge boson (Z'). The ρparameter constrains the 3-3-1 breaking scale (w) to be w>460 GeV. The quarks get consistent masses via five-dimensional effective interactions while the leptons via interactions up to six dimensions. Particularly, the neutrino small masses are generated as a consequence of the approximate lepton-number symmetry of the model. The proton is stabilized due to the lepton-parity conservation (-1)^L. The hadronic FCNCs are calculated that give a bound w>3.6 TeV and yield that the third quark generation is different from the first two. The correct mass generation for top quark implies that the minimal scalar sector as proposed is unique. By the simple 3-3-1 model, the other scalars beside the minimal ones can behave as inert fields responsible for dark matter. A triplet, doublet and singlet dark matter are respectively recognized. Our proposals provide the solutions for the long-standing dark matter issue in the minimal 3-3-1 model.

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