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Da-Xin Zhang

Publications and source records attributed to Da-Xin Zhang.

At least 19 recordsLinked to original sources
arXiv2025

Realize cosmological inflation in supersymmetric Grand Unified models with $R$-symmetry breaking

In this paper, we present a discussion for cosmological inflation based on a general renormalizable supersymmetric model which can be naturally embedded into grand unified models. Successful hybrid inflation has been realized with an effective Mexican-hat potential, while avoiding the generation of extra massless multiplets so that gauge coupling unification is maintained in the supersymmetric grand unified models. This is achieved by including $R$-symmetry violating couplings. A relatively large tensor-to-scalar ratio $r\approx 0.03$ and a spectral index $n_s\approx 0.965$ are obtained, which are expected to be further tested by future experiments. Futhermore, The hierarchy of parameters in the model can be solved at the same time, and all dimensionless parameters are in the range from 0.3 to 3 by adjustment of $R$-charges.

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arXiv2025

Modified hybrid inflation in no-scale SUGRA with suppressed $R$-symmetry breaking

A well-motivated cosmological hybrid inflation scenario based on no-scale SUGRA is considered. It is demonstrated that an extra suppressed $R$-symmetry breaking term $S^n$ with $n\geq 4$ needs to be included in order to realize successful inflation. The resulting potential is found to be similar (but not identical) to the one in the Starobinsky inflation model. A relatively larger tensor-to-scalar ratio $r\sim 10^{-2}$ and a spectral index $n_s\approx 0.965$ are obtained, which are approximately independent of $n$.

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arXiv2018

Goldstone Modes and Clebsch-Gordan Coefficients

We solve explicitly the Goldstone modes in spontaneously symmetry breaking models with supersymmetry. We find that, when more than one fields or representations contribute to the symmetry breaking, there exist identities among the Clebsch-Gordan coefficients which can be used as consistent checks on the calculations.

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arXiv2018

Goldstone Modes in Renormalizable Supersymmetric SO(10) Model

We solve the Goldstone modes in the renormalizable SUSY SO(10) model with general couplings. The Goldstones are expressed by the Vacuum Expectation Values and the Clebsch-Gordan coefficients of relevant symmetries without explicit dependence on the parameters of the model.

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arXiv2017

Couplings in Renormalizable Supersymmetric SO(10) Models

We study the most general renormalizable couplings containing Higgs $H(10)$, $D(120)$, $\overlineΔ(\overline{126})+ Δ(126)$, $A(45)$, $E(54)$ and $Φ(210)$ in the supersymmetric SO(10) models. The Clebsch-Gordan Coefficients are calculated using the maximal subgroup $SU(5)\times U(1)_X$.

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arXiv2017

Examining A Renormalizable Supersymmetric SO(10) Model

We examine a renormalizable SUSY SO(10) model without fine-tuning. We show how to construct MSSM doublets and to predict proton decay. We find that in the minimal set of Yukawa couplings the model is consistent with the experiments, while including $120_H$ to fit the data there are inconsistencies.

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arXiv2017

On the Seesaw Scale in Supersymmetric SO(10) Models

The seesaw mechanism, which is responsible for the description of neutrino masses and mixing, requires a scale lower than the unification scale. We propose a new model with spinor superfields playing important roles to generate this seesaw scale, with special attention paid on the Goldstone mode of the $U(1)_{B-L}$ symmetry breaking.

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arXiv2015

A renormalizable supersymmetric SO(10) model

A realistic grand unified model has never been constructed in the literature due to three major difficulties: the seesaw mechanism without spoiling gauge coupling unification, the doublet-triplet splitting and the proton decay suppression. We propose a renormalizable supersymmetric SO(10) model with all these difficulties solved naturally by imposing an extra discrete symmetry.

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arXiv2014

Proton decay suppression in a supersymmetric SO(10) model

We propose a mechanism for sufficient suppression of dimension-5 operators for proton decay in a supersymmetric SO(10) model. This mechanism is analogue to the double seesaw mechanism in studying neutrino masses. Only an intermediate VEV instead of an intermediate scale is required so that gauge coupling unification is maintained. The VEV is generated by introducing an anomalous U(1) symmetry whose breaking is at higher scale. The proton decay amplitudes are suppressed by this VEV over the GUT scale. We use $\textbf{45+54}$ in breaking GUT symmetry. $\textbf{120}$ is included so that fermion sector is fully realistic. Assuming a minimal fine-tuning in the Higgs doublet sector, $\textrm{tan}β$ of order one is predicted.

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arXiv2014

A renormalizable supersymmetric SO(10) model with natural doublet-triplet splitting

We propose a renormalizable supersymmetric SO(10) model where the doublet-triplet splitting problem is solved using the Dimopoulos-Wilczek mechanism. An unwanted coupling is forbidden through a filter sector. To suppress proton decay without spoiling gauge coupling unification, there is a problem in the weak doublets which requires further improvements.

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arXiv2014

Connection between proton decay suppression and seesaw mechanism in supersymmetric SO(10) models

We propose a mechanism to suppress proton decay induced by dimension-5 operators in a supersymmetric SO(10) model. Proton lifetime is directly connected with the intermediate vacuum expectation value which is responsible for the seesaw mechanism. The model shows many consistencies with the present theoretical results such as the components of the two Higgs doublets in the minimal supersymmetric standard model.

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arXiv2014

Proton decay in a supersymmetric SO(10) model with missing partner mechanism

The extended supersymmetric SO(10) model with missing partner mechanism is studied. An intermediate vacuum expectation value is incorporated which corresponds to the see-saw scale. Gauge coupling unification is not broken explicitly. Proton decay is found to satisfy the present experimental limits at the cost of fine-tuning some parameters.

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arXiv2012

A Missing Partner Model With 24-plet Breaking SU(5)

We give a missing partner model using 24-plet instead of 75-plet to break the SU(5) symmetry. Fermion masses and mixing are generated through the Georgi-Jarlskog mechanism. The model is constructed at renormalizable level at very high energy. The perturbative region is extended for the unification gauge coupling. Constrains by proton decay is also satisfied.

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arXiv2012

A Renormalizable Supersymmetric SU(5) Model

In the Supersymmetric SU(5) Model of Unification with the Missing Partner Mechanism, we present a renormalizable model using the Georgi-Jarlsog mechanism to describe the fermion masses and mixing. At the meantime the proton decay rates are also suppressed to satisfy the experimental data.

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arXiv2011

B_c meson rare decays in the light-cone quark model

We investigate the rare decays $B_c \rightarrow D_s(1968) \ell \bar{\ell}$ and $B_c\rightarrow D_s^*(2317) \ell \bar{\ell}$ in the framework of the light-cone quark model (LCQM). The transition form factors are calculated in the space-like region and then analytically continued to the time-like region via exponential parametrization. The branching ratios and longitudinal lepton polarization asymmetries (LPAs) for the two decays are given and compared with each other. The results are helpful to investigating the structure of $B_c$ meson and to testing the unitarity of CKM quark mixing matrix. All these results can be tested in the future experiments at the LHC.

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arXiv2011

Study of non-minimal SUSY SU(5) model with realistic fermion sectors

We study a supersymmetric SU(5) model with the extra Higgs multiplets of 45+\bar 45. The unification of the gauge couplings, the fermion masses and the proton lifetime are discussed in details. The dimension-five operators mediated by different colored Higgs sector can be destructive with each other. This effect serves a way of solving the longevity of proton. We analytically analyze this destructive effect in a special limit where the mixing between the 5- and 45-plets is small. Although the theory does not hold in this special limit, it is a revelatory starting point. We can relax this limit and retain the destructive effect. In a generalized parameter space, this model is in accord with experimental results.

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