An electroweak model of the SU(3)XU(l) gauge group is studied. By matching the gauge coupling constant we obtain the mass of the new neutral gauge boson to be less than 3.1 TeV. Including the constraint from muon decay, the allowed ranges of the new gauge boson masses are 1.3 TeV < MZz < 3.1 TeV and 270 GeV1 M y < 550 GeV. Within these mass ranges, the decay Z,+ Y + + Y --with ~**--+21*(1 = e , p ,~) is allowed, providing a spectacular signature at future colliders. The low energy experiments further constrain the Z -Z' mixing angle to be -5 X 5 8 1 7 X lop4.PACS number(s): 12.60. Cn, 12.15.Mm, 13.10.+q,14.70.P~ A model of SU ( 3 ) , XU( 1 ) , was introduced by Pisano and co-workers [I] and Frampton [2] recently. The former authors argues that Y--is necessary in order to avoid unitarity violation for e -e --+ W -Yat high energies; the latter looked for a sim le solution, which included

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By extending the electroweak gauge group to SU (3) L ×U (1) Y , the 331 model incorporates dilepton gauge bosons Y which do not respect individual lepton family number. We point out that, in addition to family diagonal couplings such as Y -e-e that change lepton family number by two units, dileptons may also have family non-diagonal couplings such as Y -µ-e. The latter coupling violates lepton family number by a single unit and manifests itself via lepton flavor changing decays such as µ → 3e and µ → eγ. The family nondiagonal interaction can be CP violating and typically generates extremely large leptonic electric dipole moments. We demonstrate a natural mechanism for eliminating both single unit lepton flavor violation and large leptonic CP violation. Although we focus on the 331 model, our results are applicable to other dilepton models as well, including SU (15) grand unification.

In this paper, we study the phenomenology of right-handed neutrino isosinglets. We consider the general situation where the neutrino masses are not necessarily given by m 2 D /M , where m D and M are the Dirac and Majorana mass terms respectively. The consequent mixing between the light and heavy neutrinos is then not suppressed, and we treat it as an independent parameter in the analysis. It turns out that µ − e conversion is an important experiment in placing limits on the heavy mass scale (M ) and the mixing. Mixings among light neutrinos are constrained by neutrinoless double beta decay, as well as by solar and atmospheric neutrino experiments. Detailed one-loop calculations for lepton number violating vertices are provided.

When the GUT relation on gaugino masses is relaxed, the mass and composition of the lightest neutralino are different from those in the GUT case. We discuss its phenomenological implications on the relic abundance of the neutralinos and on superparticle searches. In particular, we focus on the case where the neutral component of Winos dominates the lightest neutralino. It turns out the Wino-LSP is not a candidate for the dark matter. where g i (i =1, 2, 3) are the gauge coupling constants of the gauge groups (2) L and SU(3) C , respectively, and M i (i =1, 2, 3) the corresponding gaugino mass parameters. Note that this relation holds, independent of the particle content between the electroweak scale and the GUT scale. Therefore, eq. (1) provides an important test of the idea of the GUTs.There are, however, many well-motivated models in which the relationand a flipped SU(5) model [4] whose gauge structure is SU(5) × U(1) X . In the former, M 1 , M 2 and M 3 are unknown parameters which will be determined by string dynamics, whereas in the latter, M 1 is independent of the others. Indeed in the flipped SU(5) it has been argued [5] that, using a RG analysis, |M 1 | ≫ |M 2 | is favored to achieve the correct gauge symmetryIn this paper, we will consider phenomenological aspects of SUSY standard models without the GUT relation (1) which is assumed in most of the literature (see however refs. [6,7,8]). In particular, we are concerned with the mass ratio r ≡ M 1 /M 2 , since it is an important parameter in the neutralino mass matrix as we will explain later. We assume, as usual, that the lightest neutralino is also the lightest superparticle (LSP). To clarify its properties is thus important in SUSY phenomenology from the viewpoints of both accelerator physics and cosmology, especially when the LSP is stable due to a Z 2 symmetry called R-parity. In this paper we will mainly discuss the case 1 of |r| > 1, in which the neutral component of Winos can be a dominant composition of the LSP (see below). Note that this Wino-dominant LSP is never realized under the GUT assumption. On the other hand, some of the details on the case of |r| ≪ 1, where the LSP is mostly the Bino, have been discussed in [7].Throughout this paper, we consider the case of the minimal particle content in the SUSY standard model. With the R-parity conservation, the

The electric dipole moment of the electron, d e , is known to vanish up to threeloops in the standard model with massless neutrinos. However, if neutrinos are massive Majorana particles, we obtain the result that d e induced by leptonic CKM mechanism is non-vanishing at two-loop order, and it applies to all massive Majorana neutrino models.

We discuss a natural solution to the strong CP problem with spontaneous CP breaking in the context of SUci 3 ) X SULi2) XU,( 1) XU,,,il) with two vectorlike quarks. The gauged U,,,(l) symmetry is imposed such that eremains zero at the tree level when CP and U,,,il) are broken by singlet Higgs scalars. Flavor-changing neutral currents at the tree level are naturally suppressed because only singlet Higgs scalars are introduced. In order to agree with the experimental measurement of E and E ' / E , we find that the CP-breaking scale and the masses of the new quarks are less than 2.0 TeV and 530 GeV, respectively.

We address the effects of the new physics predicted by the SU(3) L × U(1) X model on the precision electroweak measurements. We consider both Z-Z ′ mixing and one-loop oblique corrections, using a combination of neutral gauge boson mixing parameters and the parameters S and T . At tree level, we obtain strong limits on the Z-Z ′ mixing angle, −0.0006 < θ < 0.0042 and find M Z 2 > 490GeV (both at 90% C.L.). The radiative corrections lead to T > 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.