Shaouly Bar-Shalom

Two Higgs doublets with fourth-generation fermions: Models for TeV-scale compositeness

We construct a class of two Higgs doublets models with a 4th sequential generation of fermions that may effectively accommodate the low-energy characteristics and phenomenology of a dynamical electroweak symmetry breaking scenario which is triggered by the condensates of the 4th family fermions. In particular, we single out the heavy quarks by coupling the heavier Higgs doublet ({Phi}{sub h}) which possesses a much larger VEV only to them while the lighter doublet ({Phi}{sub {ell}) couples only to the light fermions. We study the constraints on these models from precision electroweak data as well as from flavor data. We also discuss some distinct new features that have direct consequences on the production and decays of the 4th family quarks and leptons in high-energy colliders; in particular, the conventional search strategies for t{prime} and b{prime} may need to be significantly revised.

Flavor changing single top quark production channels at e+ e- colliders in the effective Lagrangian description

We perform a global analysis of the sensitivity of LEP2 and e^+e^- colliders with a c.m. energy in the range 500 - 2000 GeV to new flavor-changing single top quark production in the effective Lagrangian approach. The processes considered are sensitive to new flavor-changing effective vertices such as Ztc, htc, four-Fermi tcee contact terms as well as a right-handed Wtb coupling. We show that e^+ e^- colliders are most sensitive to the physics responsible for the contact tcee vertices. For example, it is found that the recent data from the 189 GeV LEP2 run can be used to rule out any new flavor physics that can generate these four-Fermi operators up to energy scales of \Lambda > 0.7 - 1.4 TeV, depending on the type of the four-Fermi interaction. We also show that a corresponding limit of \Lambda > 1.3 - 2.5 and \Lambda > 17 - 27 TeV can be reached at the future 200 GeV LEP2 run and a 1000 GeV e^+e^- collider, respectively. We note that these limits are much stronger than the typical limits which can be placed on flavor diagonal four-Fermi couplings. Similar results hold for \mu^+\mu^- colliders and for tu(bar) associated production. Finally we briefly comment on the necessity of measuring all flavor-changing effective vertices as they can be produced by different types of heavy physics.

Signature of heavy Majorana neutrinos at a linear collider: Enhanced charged Higgs pair production

A charged Higgs pair can be produced at an

Dijet production at hadron colliders in theories with large extra dimensions

ee

Probing the flavor changing tc vertex via tree level processes: e+ e- ---> t anti-c electron-neutrino anti-electron-neutrino, t anti-c e+ e- and t ---> c W+ W-

collider through a

Two Higgs Doublets, a 4th Generation and a 125 GeV Higgs: A Review

t

Majorana neutrinos and lepton-number-violating signals in top-quark and W-boson rare decays

-channel exchange of a heavy neutrino (

Width effects on near threshold decays of the top quark t{yields}cWW,cZZ and of neutral Higgs bosons

N

Gauge-boson-gauge-boson scattering in theories with large extra dimensions

) via

CP violation in single top quark production and decay via pp-bar --> tb-bar + X --> W{sup +}bb-bar + X within the MSSM: A possible application for measuring arg(At) at hadron colliders

{e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{H}^{+}{H}^{\ensuremath{-}}