arXiv subjects

Zhong-Jun Yang

Publications and source records attributed to Zhong-Jun Yang.

11 recordsLinked to original sources

arXiv2025

Probing the light charged Higgs boson, pseudoscalar Higgs boson, and $Z^\prime$ boson in the $U(1)_F$ model at the LHC

In this papar, we study the production and decay of a charged Higgs boson, a pseudoscalar Higgs boson, and a $Z'$ boson at the LHC within the flavor-dependent model (FDM), at the LHC. Considering the constraints from perturbative unitarity and experimental measurements (e.g., the flavor physics data, higgs signal strengths, electroweak precision observables), we investigate the relevant processes by analyzing several common LHC search channels. Motivated by the excess in $t \to b\bar{b}c$ reported by ATLAS, which suggests a charged Higgs boson with a mass near 130 GeV and consistent with B-anomaly expectations, we perform a dedicated simulation for a charged Higgs around this mass. Our results support the experimental hint and predict that this particle has a high discovery potential at the future High-Luminosity Large Hadron Collider (HL-LHC). In contrast, for the pseudoscalar and $Z'$ bosons predicted in our model, they remain beyond the reach of current experiments as well as the expected sensitivity at a 14 TeV collider with an integrated luminosity of 300 fb$^{-1}$.

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arXiv2024

Neutralino dark matter in the extension of MSSM with two triplets and singlet

In an extension of MSSM with two triplets and a singlet, called the TNMSSM, there are seven neutralinos which can enrich the study of cold dark matter if one expects that the weakly interacting massive particle (WIMP) is responsible for the observation of Planck satellite. Such a model, compared to the MSSM, can naturally offer a solution to the $μ$ problem, and its lightest neutralino, which is bino-like, can also provide a correct relic density by using the coannihilation mechanism due to the newly added triplinos. Taking into account the related experimental measurements, such as the bound on the SM-like Higgs mass, the $B$ meson rare decays, the anomalous magnetic moment of the muon $a_μ$, the Large Hadron Collider (LHC) measurements and the latest dark matter direct detection experiment LUX-ZEPLIN (LZ), the TNMSSM parameter space can be strictly limited. In respect to all the constraints mentioned above, we find that a bino-like neutralino with a mass in the region $[100, 450]~\rm{GeV}$ can successfully account for the correct dark matter relic density. Additionally, most of the viable parameter space can be tested in the near future experiments such as the Xenon-nT experiment or LHC.

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arXiv2024

On the possibility of mixed axion/neutralino dark matter in specific SUSY DFSZ axion models

We introduce four supersymmetric (SUSY) axion models in which the strong CP problem and the $μ$ problem are solved with the help of the Peccei-Quinn mechanism and the Kim-Nilles mechanism, respectively. The axion physics enriches the SUSY model by introducing axion as a dark matter candidate and, therefore, the lightest supersymmetric particle (LSP) could just be a part of the total dark matter. For this reason, axion relieves the tensions between SUSY models and numerous experimental measurements, such as the dark matter direct detection experiments and the precise measurements of anomalous magnetic moment of the muon $a_μ$. In the present paper, we investigate the constraints imposed by the latest $a_μ$ measurements and LUX-ZEPLIN (LZ) experiment on the relic density of the Higgsino-like LSP. Additionally, we consider the constraints arising from the cosmology of saxions and axinos, and their impacts on the parameter space of our models are carefully examined. For the axion constituting the remaining portion of dark matter, we find that the conventional misalignment mechanism can successfully account for the correct dark matter relic density observed by the Planck satellite.

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arXiv2023

Theoretical Corrections of $R_D$ and $R_{D^*}$

$R_{D^{(*)}}$ is the ratio of branching ratio $\overline{B} \rightarrow D^{(*)}τ\overlineν_τ$ to $\overline{B} \rightarrow D^{(*)}l\overlineν_{l}~(l=e,~μ)$. There is a gap of 2$σ_{exp}$ or more between its experimental value and the prediction under the standard model(SM). People extend the MSSM with the local gauge group $U(1)_X$ to obtain the $U(1)_X$SSM. Compared with MSSM, $U(1)_X$SSM has more superfields and effects. In $U(1)_X$SSM, we research the semileptonic decays $\overline{B} \rightarrow D^{(*)}l\overlineν_{l}$ and calculate $R_{D^{(*)}}$. The numerical results of $R_{D^{(*)}}$ are further corrected under $U(1)_X$SSM, which are much better than the SM predictions. After correction, the theoretical value of $R_{D^{(*)}}$ can reach one $σ_{exp}$ range of the averaged experiment central value.

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arXiv2022

Higgs boson decays $h\rightarrow Z γ$ and $h\rightarrow m_V Z$ in the $U(1)_X$SSM

We present a detailed analysis of the Higgs boson decays $h\rightarrow Z γ$ and $h\rightarrow m_V Z$ in the $U(1)_X$SSM, with $m_V$ denoting the meson ($ω,ρ,ϕ,J/ψ,Υ$). Using the effective Lagrangian method, we calculate the effective constants $C_{γZ}$ (CP-even) and $\tilde{C}_{γZ}$ (CP-odd) for the vertex $h γZ$, which are corrected by the new particle loop diagrams. Numerically, the ratio $Γ_{U(1)_X}(h\rightarrow Z γ)/Γ_{SM}(h\rightarrow Z γ)$ is between $1.02-1.35$. For the vector mesons $ω,ρ,ϕ$ and $J/ψ$, the ratios $Γ_{U(1)_X}(h\rightarrow m_V Z )/Γ_{SM}(h\rightarrow m_V Z)$ are mainly distributed in the range of ($1.01-1.45$). When $m_V$ represents $Υ$, the larger value of the ratio $Γ_{U(1)_X}(h\rightarrow ΥZ )/Γ_{SM}(h\rightarrow ΥZ)$ is mostly located in the range of ($1.002-1.30$). This work can provide a reference for specific types of decay processes which can be searched in LHC.

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arXiv2022

Muon conversion to an eletron in nuclei in the $B-L$ symmetric SSM

In a few years, the COMET experiment at J-PARC and the Mu2e experiment at Fermilab will probe the $μ-e$ conversion rate in the vicinity of $\mathcal{O}(10^{-17})$ for an Al target with high experimental sensitivity. Within the framework of the minimal supersymmetric extension of the Standard Model with local $B-L$ gauge symmetry (B-LSSM), we analyze the lepton flavor violating (LFV) process of $μ-e$ conversion in nuclei. Considering the constraint of the experimental upper limit of the LFV rare decay $μ\rightarrow eγ$, the $μ-e$ conversion rates in nuclei within the B-LSSM can achieve $\mathcal{O}(10^{-12})$, which is 5 orders of magnitude larger than the future experimental sensitivity at the Mu2e and COMET experiments and may be detected in the near future.

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arXiv2021

Scalar neutrino dark matter in BLMSSM

BLMSSM is the extension of the minimal supersymmetric standard model(MSSM). Its local gauge group is $SU(3)_C \times SU(2)_L \times U(1)_Y \times U(1)_B \times U(1)_L$. Supposing the lightest scalar neutrino is dark matter candidate, we study the relic density and the spin independent cross section of sneutrino scattering off nucleon. We calculate the numerical results in detail and find suitable parameter space. The numerical discussion can confine the parameter space and provide a reference for dark matter research.

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arXiv2019

Study of dark matter in the extended BLMSSM

There are strong evidences for existence of dark matter in some experiments at present. However, the question is that we do not have a reasonable explanation for dark matter in the framework of the Standard Model(SM) of particle physics. It is necessary to extend the SM in order to explain the dark matter. According to the current possible existence conditions of dark matter, we choose $χ^0_L$ and $\tilde{Y}$ as candidates for dark matter in the EBLMSSM. We study the dominant annihilation processes in detail, including $\barχ^0_Lχ^0_L(\bar{\tilde{Y}}\tilde{Y})\rightarrow \bar{l}^Il^I$ and $\barχ^0_Lχ^0_L(\bar{\tilde{Y}}\tilde{Y})\rightarrow \barν^Iν^I$. And we calculate their annihilation cross section $σ$ and relic density $Ω_D h^2$. Then we analyze the limitations of dark matter relic density on the parameters of the EBLMSSM.

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arXiv2018

Corrections to $R_{D}$ and $R_{D^{*}}$ in the BLMSSM

The deviation of the measurement of $R_{D}$ ($R_{D^{*}}$) from the Standard Model (SM) expectation is $2.3σ$ ($3.1σ$). $R_{D}$ ($R_{D^{*}}$) is the ratio of the branching fraction of $\overline{B} \rightarrow Dτ\overlineν_τ$ ($\overline{B} \rightarrow D^{*}τ\overlineν_τ$) to that of $\overline{B} \rightarrow Dl\overlineν_{l}$ ($\overline{B} \rightarrow D^{*}l\overlineν_{l}$), where $l = e$ or $μ$. This anomaly may imply the existence of new physics (NP). In this paper, we restudy this problem in the supersymmetric extension of the Standard Model with local gauged baryon and lepton numbers (BLMSSM), and give one-loop corrections to $R_{D}$ ($R_{D^{*}}$).

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arXiv2017

$Z\rightarrow l_i^{\pm}l_j^{\mp}$ processes in the BLMSSM

In a supersymmetric extension of the Standard Model(SM) where baryon and lepton numbers are local gauge symmetries (BLMSSM), we investigate the charged lepton flavor violating (CLFV) processes $Z\rightarrow l_i^{\pm}l_j^{\mp}$ after introducing the new gauginos and the right-handed neutrinos. In this model, the branching ratios of $Z\rightarrow l_i^{\pm}l_j^{\mp}$ are around ($10^{-8}\sim10^{-10}$), which approach the present experimental upper bounds. We hope that the branching ratios for these CLFV processes can be detected in the near future.

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arXiv2016

The one loop contributions to c(t) electric dipole moment in the CP violating BLMSSM

In the CP violating supersymmetric extension of the standard model with local gauged baryon and lepton symmetries(BLMSSM), there are new CP violating sources which can give new contributions to the quark electric dipole moment (EDM). Considering the CP violating phases, we analyze the EDMs of the quarks c and t. We take into account the contributions from the one loop diagrams. The numerical results are analyzed with some assumptions on the relevant parameter space. The numerical results for the c and t EDMs can reach large values.

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