arXiv subjects

Tadashi Kon

Publications and source records attributed to Tadashi Kon.

23 records · Page 2Linked to original sources

arXiv1993

Can Stop be Light Enough for TRISTAN ?

\def\nle{{\stackrel{<}{\sim}}} We examine a possibility for existence of a light supersymmetric partner of the top quark (stop) with mass 15 $\sim$ 16 GeV in the framework of the minimal supergravity GUT model. Such light stop could explain the slight excess of the high $p_{T}$ cross section of the $D^{*\pm}$-meson production in two-photon process at TRISTAN. We point out that the existence of such stop could change the dominant decay mode of gluino and could weaken substantially present experimental bounds on the mass of gluino. It seems that there is a finite parameter region allowing existence of such light stop even if we consider the present experimental data. Inversely, if such light stop was discovered at TRISTAN, masses and mixing parameters of the other SUSY partners as well as masses of the Higgs and the top will be severely constrained, for example, $m_{\tilde{g}}\simeq$85GeV, $m_{\tilde{W_{1}}}\nle$50GeV, 110GeV$\nle m_{\tilde{\ell}}\nle$140GeV, 120GeV$\nle m_{\tilde{q}}\nle$160GeV, $θ_{t}\simeq0.9$, $m_{h}\nle$ 65GeV and 130GeV$\nle m_{t}\nle$140GeV. We also discuss briefly the proton decay and the dark matter constraints.

hep-ph↗

arXiv1993

Can Stop be Light Enough ?

\def\nle{{\stackrel{<}{\sim}}} We examine a possibility for existence of a light supersymmetric partner of the top quark (stop) with mass 15 $\sim$ 20 GeV in the framework of the minimal supergravity GUT model. Such light stop could explain the slight excess of the high $p_{T}$ cross section of the $D^{*\pm}$-meson production in two-photon process at TRISTAN. We point out that the existence of such stop could change the dominant decay mode of some particles and could weaken substantially present experimental bounds on the supersymmetric parameter space. It seems that there is a finite parameter region allowing existence of the light stop even if we consider the present experimental data. Inversely, if the light stop was discovered at TRISTAN, masses and mixing parameters of the other SUSY partners as well as masses of the Higgs and the top will be severely constrained, for example, $m_{\tilde{g}} \simeq$75GeV, $m_{\tilde{W_{1}}}\nle$55GeV, 90GeV$\nle m_{\tilde{\ell}} \nle$130GeV, 100GeV$\nle m_{\tilde{q}}\nle$150GeV, $m_{h}\nle$60GeV and 115GeV$\nle m_{t}\nle$135GeV. Some phenomenological implications on the present and future experiments are also discussed.

hep-ph↗

arXiv1993

Signals for Scalar Top Quark at $ep$ Collider HERA

In the framework of the minimal supersymmetric standard model (MSSM) and the R-parity breaking model (RBM), we investigate production processes of the scalar top (stop) at HERA energies. These models are characterized by the possible existence of the light stop whose mass is lighter than those of the top quark and the other squarks. It is shown that in the MSSM the stop pair production via boson-gluon fusion gives a sizeable cross section and the most serious background $ep\rightarrow ec\bar{c}X$ could be suppressed by appropriate kinematical cuts. We also show that in the RBM the stop is singly produced in the neutral current processes and we have a clear signal as a sharp peak in the Bjorken parameter $x$ distribution of the scattered electron.

hep-ph↗

arXiv1993

Polarization Effects in Scalar Lepton Production at High Energy $γγ$ Colliders

We investigate the charged scalar lepton production processes $γγ\to{\widetilde{\ell}}^{+}{\widetilde{\ell}}^{-}$ at high energy $γγ$ colliders in the framework of the minimal supersymmetric standard model (MSSM). Here the high energy $γ$ beams are obtained by the backward Compton scattering of the laser flush by the electron in the basic linear TeV $ee$ colliders. We consider the polarization of the laser photons as well as the electron beams. Appropriate beam polarization could be effective to enhance the cross section and to extract the signal from the dominant background $γγ\to W^{+}W^{-}$.

hep-ph↗

arXiv1993

SUSY at High Energy $eγ$ and $γγ$ Colliders

We investigate the sparticle production processes $eγ\goto \sele\sz1$ and $γγ\goto \sfermion\overline{\sfermion}$ at high energy $eγ$ and $γγ$ colliders in the framework of the minimal supersymmetric standard model (MSSM). It will be shown that the $eγ$ colliders would be more suitable in searching for the heavy selectrons than $ee$ colliders because of the low mass threshold of the process $eγ\goto \sele\sz1$. We show that the standard background processes $eγ\goto νW$ and $eZ$ can be suppressed in terms of initial beam polarization as well as the kinematical cuts on the energy and angle of the final electron. Moreover, it will be argued that the experimental measurements of the cross sections for the processes $eγ\goto \sele\sz1$ and $γγ\goto \sfb\sf$ could enable us to constrain the basic parameters in the MSSM. This is originated from the simplicity of SUSY parameter dependence of these processes. We also give comments on the stop production at $e^{+}e^{-}$ colliders with the longitudinally polarized electron beams.

hep-ph↗