[en] We discuss the hadron matrix elements of QCD and electroweak penguin operators in K → ππ using nonlinear sigma model with scalar resonances. The scalar mesons are introduced as a nonet representation under flavour SU(3) transformation. The propagators of the scalar resonances have the effect of resuming a certain class of chiral corrections to the matrix elements to all order in chiral perturbation theory. Using these results, the impact on the physical observable in kaon decay, ΔI=1/2 rule and ε'/ε, are discussed. We show the effects of σ meson are of great importance in K → ππ when mass of the σ meson is near to the kaon threshold due to propagator enhancement. However our results show that we are still missing some large amount of contributions to explain both of ΔI=1/2 and ε'/ε consistently. An plausible explanation may be non-factorizable contributions, thus chiral loop corrections to the matrix elements may help us with deep understanding on the decay K → ππ. (author)

[en] We discuss the hadronic matrix elements of the QCD and electroweak penguin operators in kaon decay, K → ππ, using nonlinear sigma model with scalar resonances. The scalar mesons are introduced as a nonet representation of flavor SU(3) transformation. The propagators of these scalar resonances have effect of resuming a certain class of chiral corrections to the matrix elements to all order in chiral perturbation theory. Using this model impact on the physical observable in kaon decay, ΔI=1/2 rule and ε'/ε, are discussed. We show the effects of σ meson are of great importance in kaon decay when mass of the σ meson is near to the kaon mass due to propagator enhancement. However results show that we are still missing some large amount of contributions to explain both of ΔI=1/2 rule and ε'/ε consistently. (author)

[en] We discuss top quark production and its subsequent decay at lepton colliders including both QCD corrections and anomalous γ/Z - tt-bar couplings. The off-diagonal spin basis for the top and anti-top quarks is shown to be useful to probe the anomalous couplings

[en] At the International Linear Collider it will be possible to study the production cross section of top quarks at threshold with very high precision. Therefore, it is necessary to have precise theoretical predictions within the Standard Model in order to determine important physical quantities like the top quark mass or width. Furthermore it is necessary to investigate the effects of theories beyond the Standard Model on the production cross section. In this talk we consider one-loop corrections within Two-Higgs-Doublet Model and the Minimal Sypersymmetric Standard Model

[en] We discuss polarized proton-positron scattering in the context of the excess of large Q² events at HERA. We define and estimate a polarized asymmetry to examine two scenarios, the contact interaction and the stop scenario with broken R-parity. This asymmetry exhibits a characteristic behavior depending on the scenarios. Thus the polarized experiment at HERA will provide with a good test for these models. (author)

No abstract available

[en] We compute the last missing piece of the two-loop O(αα_s) corrections to γt t-bar vertex at the t t-bar threshold due to the exchange of a W boson and a gluon. This contribution constitutes a building block of the top quark threshold production cross section at electron positron colliders.

[en] We discuss top quark production and its subsequent decay at e⁺e^- colliders including QCD corrections and anomalous coupling in γ/Z-t-t-bar vertices. In off-diagonal spin basis, azimuthal angular distribution of decay product of polarized top quarks is shown to be useful to probe γ/Z-t-t-bar vertices

[en] We discuss W_γ production in polarized pp collisions at the RHIC energy. We point out that the RHIC collider has two advantages over other hadron colliders to measure the characteristic features of W_γ production: (1) the RHIC energy is not too high, and (2) polarized beams are available. We calculate the tree level cross section for W_γ production using a generic spin basis for W and study both the angular dependence and spin correlation. (author)

[en] We consider a different power counting in potential NRQCD by incorporating the static potential exactly in the leading order Hamiltonian. We compute the leading relativistic corrections to the inclusive electromagnetic decay ratios in this new scheme. The effect of this new power counting is found to be large (even for top). We produce an updated value for the η_b decay to two photons. This scheme also brings consistency between the weak coupling computation and the experimental value of the charmonium decay ratio.