An improved flipped SU(5)×U(1) model from the four-dimensional string

We discuss a four-dimensional string model whose effective field theory is a supersymmetric flipped SU(5)×U(1) GUT with the following properties.

• •- The quark and lepton mass matrices have a hierarchical structure and all Cabibbo-Kobayashi-Maskawa mixing angles can be non-zero.
• •- There is a natural splitting of Higgs doublets and triplets.
• •- A novel seesaw mechanism gives light left-handed neutrinos.
• •- The gauge group is reduced to the standard model SU(3)_C×SU(2)_L×U(1)_Y at a large mass scale close to M_P.

Extensive use is made of non-renormalizable superpotential couplings which may arise from couplings to identifiable massive modes, and are restricted by an R symmetry and the requirements of flatness is some field directions.     

More flipped SU(5)×U(1) baryosynthesis

We supplement a previous discussion of baryosynthesis in flipped SU(5)×U(1) GUTs by including (1) the large incoherent field energy density which is likely SU(5) is broken, and (2) the possibility of additional Higgs triplet fields suggested by four dimensional string model-building. We consider strong (weak) reheating scenarios in which the Universe is (is not) SU(5) symmetric after inflation. We find an adequate baryon asymmetry subsequent to strong reheating, whatever the number of Higgs triplets (although beware of possible difficulties with quasi-stable relic particles), whereas weak reheating requires at least two Higgs triplets.     

Yukawa couplings in SU(3)×SU(2)×U(1)Y orbifold models

We analyze the Yukawa couplings of the first SU(3)×SU(2)×U(1)_Y orbifold models recently obtained. In these models the rank is naturally lowered due to the presence of a Fayet-Iliopoulos term associated with an “anomalous” U(1) in the four-dimensional theory. It is shown that the phenomenological viability of the models selects a favoured class of vacua. In particular, for the specific examples considered, some twisted fields with one moded oscillator acting, must acquire non-vanishing VEVs. However other possibilities may exist. We also find that all the baryon and lepton violating operators can be, in general, avoided in a completely natural way.     

A model with flavor-dependent gauged U(1)_(B-L_1)×U(1)_(B-L_2-L_3) symmetry

We propose a new model with flavor-dependent gauged U(1)_(B-L_1)×U(1)_(B-L_2-L_3) symmetry in addition to the flavor-blind symmetry in the Standard Model. The model contains three right-handed neutrinos to cancel gauge anomalies and several Higgs bosons to construct the measured fermion masses. We show the generic features of the model and explore its phenomenology. In particular, we discuss the current bounds on the extra gauge bosons from the K and B meson mixings as well as the LEP and LHC data, and focus on their contributions to the lepton flavor violating processes of ?_(i+1) →?_iγ(i=1,2).     

弱电统一理论——SU(3)×U(1)模型

本文提出了一个对称性破缺前不仅左、右对称, 而且中微子(或反中微子)与荷电轻子、反轻子的弱作用也相同的SU(3)×U(1)模型. 这一模型无三角反常; 导出了sin²θ_w≤1/4; 在低能范围内与标准模型一致. 我们反轻子数推广为轻子荷. 证明了只有轻子荷才是严格守恒的, 各代轻子数分别守恒只能近似成立. 夸克不仅带有重子数、电荷, 而且也带有轻子荷. 本模型预言有μ_R→e_R+ν_eL+ν_μR, e^－+e^－→μ^－+μ^－等现象.     

An SU (3)_L×U(1)_X Electroweak Model

We studied an SU(3)_L×U(1)_X electroweak model. By requiring M2z1-M2w/ cos²θw to be less than experimental value we abtain a lower bound on M_Z′ The relation between M_Z′ and M_U (M_V) then gives a lower bound on M_U (M_V). We further consider the K_L－K_S mass difference due to Z′ exchange and obtain stronger lower bounds on M_Z′ and M_U (M_V).     

Non-standard Higgs bosons inSU(2)×U(1) radiative corrections

The 1-loop renormalization of theSU(2)×U(1) electroweak gauge theory with two Higgs doublets is performed in the on-shell scheme with finite self energies and vertices. Assuming different vacuum expectation values for the scalar doublets, which yield enhanced Yukawa couplings to fermions, we calculate the effects of the additional Higgs bosons in the radiative corrections to the leptonic processes:μ-decay,v _μ e-scattering, ande ⁺ e ^?→μ ⁺ μ ^?,τ ⁺ τ ^? with longitudinal polarization at PETRA and LEP/SLC energies. It is found that large effects occur in theM _W ?M _Z mass relation, the determination of sin² θ _w from \(\sigma (v_\mu e)/\sigma (\bar v_\mu e)\) and thee ⁺ e ^? forward-backward and polarization asymmetries, if either the charged Higgs or the additional neutral scalar/pseudoscalar are heavy. Enhancement effects and effects of light neutral bosons can better be observed in thee ⁺ e ^?→τ ⁺ τ ^? integrated cross section.     

SU(3)_C×SU(2)_I×U(1)_Y复合轻子理论

假定HiggsYukawa耦合是宇称不守恒的唯一来源，通过取三代并引进超对称性，从而建立了一个SU（3）C×SU（2）I×U（1）Y复合轻子理论。     

Orbifold compactifications with three families of Su(3) ×Su(2) ×U(1)n

We construct several N = 1 supersymmetric three-generation models with SU(3)×SU(2)×U(1)ⁿ gauge symmetry, obtained from orbifold compactification of the heterotic string in the presence of constant gauge-background fields. This Wilson-line mechanism also allows us to eliminate extra colour triplets which could mediate fast proton decay.     

SU(3)L×U(1)X

提出了一个基于SU（3）     

Axion cosmology in automatic E6 × U(1) models

An automatic E₆ × U(1) axion model is constructed which is cosmologically consistent, predicts three families of fermions at low energies, and admits cosmic strings capable of seeding galaxy formation.     

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.     

Doubly charged pseudo-goldstone bosons and dynamical SU(2) × U(1) breaking

An alternative structure of electroweak symmetry breaking based on an SU(4)/SU (2) symmetry breaking pattern is discussed. An effective chiral lagrangian describing the pseudo-Goldstone bosons and gauge bosons is constructed and their interactions are analyzed. It is shown that the model contains doubly charged pseudo-Goldstone bosons which couple to two similarly charged W's. The question of vacuum alignment is considered, and it is shown that if an additional discrete symmetry is imposed, a custodial SU (2) preserving vacuum is a global minimum of the potential (for a range of coefficients in the effective chiral lagrangian).