Z−Z′ mixing and oblique corrections in anSU(3)×U(1) model

We address the effects of the new physics predicted by theSU(3) _l ×U(1) _X model on the precision electroweak measurements. We consider bothZ–Z mixing and one-loop oblique corrections, using a combination of neutral gauge boson mixing parameters and the parametersS andT. At tree level, we obtain strong limits on theZ–Z mixing angle, –0.0006<0.0042 and="> 490$$ " align="middle" border="0"> GeV (both at 90% C.L.). The radiative corrections lead toT>0 if the new Higgs are heavy, which bounds the Higgs masses to be less than a few TeV.S can have either sign depending on the Higgs mass spectrum. Future experiments may soon place strong restrictions on this model, thus making it eminently testable.     

On superstring-inspired SU(3) × SU(2) × (U(1))2 models with SO(10) unification

Alternative compactification of the heterotic superstring can give rise to a residual four-dimensional SO(10) gauge symmetry for the observable sector. We consider a model with gauge group SU(3) × SU(2) × (U(1))², resulting from the Hosotani breaking of SO(10), study its further gauge symmetry breaking and calculate the particle spectrum. We find that all breakings can occur close to the weak scale; the top mass lies preferentially between 40 and 60 GeV, the second Z boson mass is O(200–400) GeV. The sparticle spectrum is quite heavy, apart possibly from a light chargino, whose mass can be as light as O(30) GeV.     

Lepton Flavor Violating Z→lIlJ in SO(3) Gauge Extension of SM

The SO(3) gauge extension of SM, which is proposed to present a successfulexplanation for the observed small masses of neutrino and the nearly tri-bimaximal neutrino mixing, predicted the vector-like SO(3) triplet Majorana neutrinos and SU_L(2) double Higgs bosons. In this work we calculate branching ratios of the charged lepton flavor violating decays l_Il_JV (V=γ,Z) induced by these Majorana neutrinos and Higgs bosons. We find that under the model parameters constrained by experimental bounds on the decays Z→l_Il_J, the branching ratio of decays l_I→l_Jγ can be up to 10^-10, which may be accessible at the future experiments.     

带有分数电荷、磁单极子和异常光子的SO(10)×SO(8)模型

本文构造了一个SO(10)×SO(8)大统一模型. 它能容纳带分数电荷(例如e/2或e/3)的色单态粒子, 并且满足Dirac量子化条件(当磁荷取值1/2e时). 理论预言了四代通常费米子和四代异常费米子. 特别是模型中存在着不同于通常光子的异常光子, 这此可以在今后的高能实验中去验证.     

Study of B s 0 → µ+µ− and B d 0 → µ+µ− decays in flavor-changing Z′ models

Recently, the first evidence for the decay B _s ⁰ → μ ⁺ μ ^? has been announced by the LHCb Collaboration and the measured branching ratio B( _s ⁰ → μ ⁺) = (3.2 _?1.2 ^+1.5 ) × 10^?9 is in good agreement with the standard model (SM) expectation. It has also reported an upper limit for B(B _d ⁰ → μ ⁺ μ ^?) < 9.4 × 10^?10 at 95% confidence level. In this paper, we study the B _s ⁰ → μ ⁺ μ ^? and B _d ⁰ → μ ⁺ μ ^? rare decays in flavor-changing Z′ model. Our estimated branching ratios are enhanced from their SM values and provide signals for new physics.     

SO(10)模型中的一类Jackiw-Rebbi零能束缚态

本文讨论了SO(10)大统一模型的球对称磁单极以及在这个模型中的Jackiw-Rebbi型费米子-磁单极零能束缚态问题. 结果表明, 在这个理论中并不存在这样的零能束缚态.     

Search for top quark FCNC couplings in Z′ models at the LHC and CLIC

The top quark is the heaviest particle to date discovered, with a mass close to the electroweak symmetry breaking scale. It is expected that the top quark would be sensitive to the new physics at the TeV scale. One of the most important aspects of the top quark physics can be the investigation of the possible anomalous couplings. Here, we study the top quark flavor changing neutral current (FCNC) couplings via the extra gauge boson Z′ at the Large Hadron Collider (LHC) and the Compact Linear Collider (CLIC) energies. We calculate the total cross sections for the signal and the corresponding Standard Model (SM) background processes. For an FCNC mixing parameter x=0.2 and the sequential Z′ mass of 1 TeV, we find the single top quark FCNC production cross sections 0.38(1.76) fb at the LHC with $\sqrt{s_{pp}}=7(14)$ TeV, respectively. For the resonance production of sequential Z′ boson and decays to single top quark at the Compact Linear Collider (CLIC) energies, including the initial state radiation and beamstrahlung effects, we find the cross section to be 27.96(0.91) fb at $\sqrt{s_{e^{+}e^{-}}}=1(3)$ TeV, respectively. We make the analysis to investigate the parameter space (mixing-mass) through various Z′ models. It is shown that the results benefit from the flavor tagging.     

SO(10)×SU(4) CHIRAL PREON MODEL SATISFYING COMPLEMENTARITY PRINCIPLE

We extended the MAC principle to the case for semisimple metacolor gauge group and the constructed and SO(10)×SU(4) chrial preon model which satisfies the complementarity principle.This model had a unique solution and thus predicted 4 generations of quarks and leptons without exotics.The generation gauge group was intruduced and the breaking of mass degeneracy among different generations was investigated.     

Extra Z′-boson in (ν&#x0304;)N-elastic and some quasielastic processes

The contribution of an extra Z′-boson to the elastic ⁽ν&#x0304;⁾p-scattering, π⁰ neutrino-production on nuclei and some diffractive reactions is calculated in the frame of the superstring inspired E₆-model. We give quantitative estimations of this contribution and its dependence on model parameters.     

SO(6) SO(5)同位标量因子的计算

本文用求约化矩阵元和逐步计算原理相互结合的方法计算了部分SO(6) SO(5)同位标量因子.     

Z′ in the 3-3-1 model

Phenomenological implications of the Z′ in SU(3) × SU(3) × U(1) extension of the standard model are studied. We find that the current experimental value of R_b puts severe constraints on the Z′ mass in this model. The model improves slightly the fit for large E_T jet cross section observed by CDF.     

SO(6)SO(5)同位标量因子的计算

本文用求约化矩阵元和逐步计算原理相互结合的方法计算了部分SO(6)SO(5)同位标量因子。     

满足互补原理的SO(10)×SU(4)手征前子模型

本文反MAC (Most Attractive Channel)规则推广到半单超色规范群情形,构造了满足互补原理的SO(10)×SU(4)手征前子模型.该模型给出唯一解,预言了4代夸克和轻子,没有例外粒子出现.本文引入了代规范群SU(2)_g讨论了不同代费米子质量简并性的破缺.