G. Eilam

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-

The reactions e+e- -> t bar-c nu_e bar-nu_e, t bar-c e+ e- are very sensitive probes of the flavor-changing-scalar couplings which can occur in a model with one extra Higgs doublet. At the Next Linear Collider, with a center of mass energy of sqrt{s}=0.5--2 TeV, several hundreds and up to thousands of such events may be produced if the mass of the light neutral Higgs is a few hundred GeV. We also briefly comment on the decays t -> c W+ W-, t -> c Z Z. All of these reactions are severely suppressed in the Standard Model

Implications of aW+W−(ZZ)-Higgs boson- tc¯interaction fore+e−→tc¯νeν¯e,tc¯e+e−, tc¯Z and fort→cW+W−,cZZin a two Higgs doublet model

The Standard Model with one extra Higgs doublet may give rise to enhanced TREE-LEVEL flavor-changing-scalar coupling of a neutral Higgs to a pair of top-charm quarks. This coupling may drive a large TREE-LEVEL effective W^+W^-(ZZ) - Higgs - t c-bar interaction. As a result we find that the reactions e^+e^- -> t c-bar \nu_e \nu_e-bar, t c-bar e^+ e^-, t c-bar Z and the two rare top decays t -> cW^+W^-, t -> cZZ become very sensitive probes of such an effective interaction. The most promising ones, e^+e^- -> t c-bar \nu_e \nu_e-bar, t c-bar e^+ e^-, may yield several hundreds and up to thousands of such events at the Next Linear Collider with a center of mass energy of \sqrt{s}=0.5 - 2 TeV if the mass of the lightest neutral Higgs is a few hundred GeV. The rare decays t -> cW^+W^- and t -> cZZ may be accessible at the LHC if the mass of the lightest neutral Higgs lies in the narrow window 150 GeV < m_h < 200 GeV.

Large tree-level {ital CP} violation in {ital e}{sup +}{ital e}{sup {minus}}{r_arrow}{ital t{bar t}H}{sup 0} in the two-Higgs-doublet model

We find a large CP violation effect within the two-Higgs-doublet model for the reaction

The Flavor changing top decay t ---> c sneutrino or sneutrino ---> t anti-c in the MSSM without R-parity

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R-parity violation, sneutrino mixing phenomena and CP-violation in p \bar p -> sneutrino -> l^+ l^- + X

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Flavor changing top decay t{r_arrow}c{tilde {nu}} or {tilde {nu}}{r_arrow}t{bar c} in the MSSM without {ital R} parity

\ensuremath{\rightarrow}tt\ifmmode\bar\else\textasciimacron\fi{}

Flavor changing top decayt→cν̃orν̃→tc¯in the MSSM withoutRparity

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R-parity violation and uses of the rare decayν̃→γγin hadron and photon colliders

at future linear colliders. The CP asymmetry arises already at the tree level as a result of interference between diagrams with

{ital R}-parity violation and uses of the rare decay {tilde {nu}}{r_arrow}{gamma}{gamma} in hadron and photon colliders

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