Discovery and Identification of W' Bosons at e+e- Colliders

We report on studies of the sensitivity to extra gauge bosons of the reactions e^+ e^- -> nu nubar gamma and e gamma -> nu q + X to extract discovery limits for W' 's. The discovery potential for a W' is, for some models, comparable to that of the LHC. These processes may be also useful for determining W' and Z' couplings to fermions which would complement measurements made at the Large Hadron Collider.Comment: 3 pages, 2 postscript figures, Presented at the DPF2000 Conference, August 9-12, 2000, The Ohio State University, Columbus, Ohi

Report of the Subgroup on Alternative Models and New Ideas

We summarize some of the work done by the P3 subgroup on Alternative Models and New Ideas. The working group covered a broad range of topics including a constrained Standard Model from an extra dimension, a discussion of recent ideas addressing the strong CP problem, searches for doubly charged higgs bosons in e gamma collisions, and an update on discovery limits for extra neutral gauge bosons at hadron colliders. The breadth of topics reflects the many ideas and approaches to physics beyond the Standard Model.Comment: 10 pages, 5 figures. Contributed to the APS/DPF/DPB Summer Study on the Future of Particle Physics (Snowmass 2001), Snowmass, Colorado, 30 Jun - 21 Jul 200

New Solution for Neutrino Masses and Leptogenesis in Adjoint SU(5)

We investigate baryogenesis via leptogenesis and generation of neutrino masses and mixings through the Type I plus Type III seesaw plus an one-loop mechanism in the context of Renormalizable Adjoint SU(5) theory. One light neutrino remains massless, because the contributions of three heavy Majorana fermions \rho_0, \rho_3 and \rho_8 to the neutrino mass matrix are not linearly independent. However none of these heavy fermions is decoupled from the generation of neutrino masses. This opens a new range in parameter space for successful leptogenesis, in particular, allows for inverted hierarchy of the neutrino masses.Comment: 16 pages, 4 figures; references added and typos fixe

Extracting W Boson Couplings from the e+e−e^{+}e^{-} Production of Four Leptons

We consider the processes $e^{+}e^{-}\rightarrow \ell^{+} \ell^{\prime -}\nu \bar{\nu}^{\prime}$, including all possible charged lepton combinations, with regard to measuring parameters characterizing the $W$ boson. We calculate at what level these processes can be used to measure anamolous triple-boson vertice coupling parameters for the cases of $e^{+}e^{-}$ colliders at 500 $GeV$ and 1 $TeV$ center of mass energies.Comment: 13 pages,OCIP/C-93-

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

Charged Lepton Flavour Violation from Massive Neutrinos in Z Decays

Present evidences for neutrino masses and lepton flavour mixings allow to predict, in the Standard Model with light neutrinos, branching rates for the decays Z --> e mu, mu tau, e tau of less than 10^{-54}, while present experimental exclusion limits from LEP 1 are of order 10^{-5}. The GigaZ option of the TESLA Linear Collider project will extend the sensitivity down to about 10^{-8}. We study in a systematic way some minimal extensions of the Standard Model and show that GigaZ might well be sensitive to the rates predicted from these scenarios.Comment: 24 pages, 4 figures, LaTeX, uses axodraw.st