Phenomenology of the SU(2)(L) x SU(2)(I) x U(1)(Y) x U(1)(Y\u27) model

We consider the effective low-energy SU(2) L x SU(2)I x U(1)Y x U(1)Y\u27 model, which is based on the E6 grand unification theory. SU(2)I is a subgroup of SU(3) R and commutes with the electric charge operator.;Higgs bosons in the Standard Model and two-Higgs doublet models are reviewed and studied first. The flavor-changing neutral currents and their effects on the anomalous magnetic moment of the muon are discussed. Bounds on masses of Higgs bosons are obtained by requiring that the vacuum is stable and perturbation theory is valid up to a large scale. We introduce Higgs multiplets including two neutral doublets to break down SU(2)L x SU(2)I x U(1)Y x U(1) Y\u27 to U(1) em. An upper bound of about 150 GeV to the lightest neutral Higgs scalar mass is found.;The gauge bosons corresponding to SU(2) I are charge-neutral. Production and effects of W I bosons are reviewed first. Mixings among neutral gauge bosons appear naturally. Electroweak precision experiments, including Z-pole experiments, mW measurements and low-energy neutral current experiments are used to put indirect constraints on masses of the extra neutral gauge bosons and the mixings between them and the ordinary Z boson. We also consider the possible constraint from a proposed measurement at Jefferson Lab of the proton\u27s weak charge. It is found that the mixing angles are very small, namely ;theta; ≤ 0.005. The lower bound for the mass of the lightest extra neutral gauge boson is found to be about 560--800 GeV, which is comparable with the current direct search limit. Low-energy neutral current experiments give the strongest bounds on the lightest extra neutral gauge boson.;Fermions reside in the 27 fundamental representation of E6. We study the pair production of heavy charged exotic leptons at e+e- colliders in this model. In addition to the standard gamma and Z boson contributions, a t-channel contribution due to WI-boson exchange, which is unsuppressed by mixing angles, is quite important. We calculate the cross section, the left-right and forward-backward asymmetries, and discuss how to differentiate different models

Vacuum Stability Bounds in the Two-Higgs Doublet Model

In the standard model, the requirements of vacuum stability and the validity of perturbation theory up to the unification scale force the mass of the Higgs boson to be approximately between 130 GeV and 180 GeV. We re-examine these requirements in the (non-supersymmetric) two-Higgs doublet model, in the light of the large top quark mass, and constrain the masses of the Higgs bosons in this model. It is found that the mass of the charged Higgs boson must be lighter than 150 GeV. This bound is below the lower bound in the popular model-II two-Higgs doublet model, and thus we conclude that this model cannot be valid up to the unification scale. The bounds on the neutral Higgs scalars are also discussed.Comment: 8 pages, 4 figure

The Anomalous Magnetic Moment of the Muon and Higgs-Mediated Flavor Changing Neutral Currents

In the two-Higgs doublet extension of the standard model, flavor-changing neutral couplings arise naturally. In the lepton sector, the largest such coupling is expected to be $\mu-\tau-\phi#. We consider the effects of this coupling on the anomalous magnetic moment of the muon. The resulting bound on the coupling, unlike previous bounds, is independent of the value of other unknown couplings. It will be significantly improved by the upcoming E821 experiment at Brookhaven National Lab.Comment: 7 pages Latex, 2 figure

t-channel production of heavy charged leptons

We study the pair production of heavy charged exotic leptons at e+ e- colliders in the SU(2)_L x SU(2)_I x U(1)_Y model. This gauge group is a subgroup of the grand unification group E6; SU(2)_I commutes with the electric charge operator, and the three corresponding gauge bosons are electrically neutral. In addition to the standard photon and Z boson contributions, we also include the contributions from extra neutral gauge bosons. A t-channel contribution due to W_I-boson exchange, which is unsuppressed by mixing angles, is quite important. We calculate the left-right and forward-backward asymmetries, and discuss how to differentiate different models.Comment: Increased discussion of experimental signatures. Version accepted by PR

Chargino contributions to ϵ′/ϵ\epsilon^{\prime}/ \epsilon in the left-right supersymmetric model

We analyze the chargino contributions to the CP violating ratio $\epsilon^{\prime}/\epsilon$ in the left-right supersymmetric model. We study the possibility that these contributions alone can saturate the experimental value of $\epsilon^{\prime}/\epsilon$. We derive conservative bounds on supersymmetric flavor violation parameters in the up squark LL, RR, LR and RL sectors, using the mass insertion approximation. While the LL bounds are found to be consistent with the MSSM values, the LR constraints are new and much stronger.Comment: 14 pages, 1 figure, 2 table

Large Electric Dipole Moments of Heavy Neutrinos

In many models of CP violation, the electric dipole moment (EDM) of a heavy charged or neutral lepton could be very large. We present an explicit model in which a heavy neutrino EDM can be as large as $10^{-16}$ e-cm, or even a factor of ten larger if fine-tuning is allowed, and use an effective field theory argument to show that this result is fairly robust. We then look at the production cross section for these neutrinos, and by rederiving the Bethe-Block formula, show that they could leave an ionization track. It is then noted that the first signature of heavy neutrinos with a large EDM would come from $e^+e^-\to \bar{N}N\gamma$, leading to a very large rate for single photon plus missing energy events, and the rate and angular distribution are found. Finally, we look at some astrophysical consequences, including whether these neutrinos could constitute the UHE cosmic rays and whether their decays in the early universe could generate a net lepton asymmetry.Comment: 22 pages, 9 figure

Lepton Flavor Violation in the Two Higgs Doublet Model type III

We consider the Two Higgs Doublet Model (2HDM) of type III which leads to Flavour Changing Neutral Currents (FCNC) at tree level in the leptonic sector. In the framework of this model we can have, in principle, two situations: the case (a) when both doublets acquire a vacuum expectation value different from zero and the case (b) when only one of them is not zero. In addition, we show that we can make two types of rotations for the flavor mixing matrices which generates four types of lagrangians, with the rotation of type I we recover the case (b) from the case (a) in the limit $\tan \beta \to \infty$, and with the rotation of type II we obtain the case (b) from (a) in the limit $\tan \beta \to 0.$Moreover, two of the four possible lagrangians correspond to the models of types I and II plus Flavor Changing (FC) interactions. The analitical expressions of the partial lepton number violating widths $\Gamma (\mu \to eee)$ and $\Gamma (\mu \to e\gamma)$are derived for the cases (a) and (b) and both types of rotations.$$In all cases these widths go asymptotically to zero in the decoupling limit for all Higgses. We present from our analysis upper bounds for the flavour changing transition $\mu \to e,$ and we show that such bounds are sensitive to the VEV structure and the type of rotation utilized.Comment: 7 pages RevTeX4, 4 figures postscript, new section added and some new reference

Delta M_K and epsilon_K in the left-right supersymmetric model

We perform a complete analysis of $\Delta S=2$ processes in the kaon system and evaluate $\Delta M_K$ and $\epsilon_K$ in the left-right supersymmetric model. We include analytic expressions for the contributions of gluinos, neutralinos and charginos. We obtain general constraints on off-diagonal mass terms between the first two generations of both down-type and up-type squarks. In the down-squark sector, we compare the results with gluino-only estimates. In the up-squark sector, we find a complete set of bounds on all combinations of chirality conserving or chirality flipping parameters. Finally, we comment on the size of the bounds obtained by imposing left-right symmetry in the squark sector.Comment: 22 pages, 1 figure and 4 table

b -> s gamma in the left-right supersymmetric model

The rare decay $b \to s \gamma$ is studied in the left-right supersymmetric model. We give explicit expressions for all the amplitudes associated with the supersymmetric contributions coming from gluinos, charginos and neutralinos in the model to one-loop level. The branching ratio is enhanced significantly compared to the standard model and minimal supersymmetric standard model values by contributions from the right-handed gaugino and squark sector. We give numerical results coming from the leading order contributions. If the only source of flavor violation comes from the CKM matrix, we constrain the scalar fermion-gaugino sector. If intergenerational mixings are allowed in the squark mass matrix, we constrain such supersymmetric sources of flavor violation. The decay $b \to s \gamma$ sets constraints on the parameters of the model and provides distinguishing signs from other supersymmetric scenarios.Comment: 12 figure

Bd0−Bˉd0B^0_d-{\bar B}^0_d mixing in the left-right supersymmetric model

We analyze $B^0_d-{\bar B}^0_d$ mixing in a fully left-right supersymmetric model. We give explicit expressions for all the chargino, gluino, gluino-neutralino and neutralino amplitudes involved in the process. We calculate the mass difference $\Delta m_d$ and CP asymmetry $a_{J/\psi K_s}$ in both the constrained case (where the only flavor violation comes from the Cabibbo-Kobayashi-Maskawa matrix) and the unconstrained case (including soft supersymmetry breaking terms). The constrained case does not contain any new information beyond the supergravity-inspired MSSM. In the unconstrained case, the main contribution to $B^0_d-{\bar B}^0_d$ and the CP asymmetry is due to either gluino diagrams, if the dominating flavor mixing arises in the down squark sector, or chargino diagrams, if the dominant flavor mixing comes from the up squark sector. We include numerical results and compare this analysis with the ones performed in other models.Comment: 26 pages, 10 figure