Abstract:
We discuss the sensitivity to four-fermion contact interactions of the process of fermion-pair production at the e^+ - e^- Linear Collider (LC), with E_{CM}=0.5 TeV and longitudinally polarized electron beam. The analysis is based on polarized integrated cross sections with optimal cuts. Beam polarization and optimization are shown to have a crucial role in the derivation of model-independent constraints on the new interactions from the data.

Abstract:
We study the D^{+} -> sigma pi^{+}, D^{+} -> rho^0 pi^{+}, B^{-} -> sigma pi^{-}, B^{-} -> rho^0 pi^{-} and \bar{B}^0 -> rho^{\pm} pi^{\mp} decays in a valence quark triangle model, incorporating chiral symmetries. We find a good agreement with recent experimental data for D^{+} -> sigma pi^{+} and for D^{+} -> rho^0 pi^{+}. We point out that a "long-distance" contribution due to the axial vector a_1 meson pole, calculated by using chiral symmetry, can be relevant to explain D^{+}-> rho^0 \pi^{+} and for lowering the ratio R=Br(\bar{B}^0 -> rho^{\pm} pi^{\mp})/Br(B^{-} -> rho^0 pi^{-}) to be consistent with its phenomenological determination, within the large experimental uncertainity.

Abstract:
We discuss electron-electron contact-interaction searches in the process e^+e^- -->e^+e^- at a future e^+e^- Linear Collider with c.m. energy \sqrt{s}=0.5 TeV and with both beams longitudinally polarized. Our analysis is based on the measurement of the polarized differential cross sections, and allows to simultaneously take into account the general set of contact interaction couplings as independent, non-zero, parameters thus avoiding simplifying, model-dependent, assumptions. We evaluate the corresponding model-independent constraints on the coupling constants, emphasizing the role of beam polarization, and make a comparison with the case of e^+e^- -->\mu^+\mu^-.

Abstract:
We discuss the time dependent interferences between $K_L$ and $K_S$ in the decays in $3\pi$ and $\pi\pi\gamma$, to be studied at interferometry machines such as the $\phi$-factory and LEAR. We emphasize the possibilities and the advantages of using interferences, in comparison with width measurements, to obtain information both on $CP$ conserving and $CP$ violating amplitudes. Comparison with present data and suggestions for future experiments are made.

Abstract:
We discuss the potential of NLC500 and NLC1000 to probe Z-Z' mixing and mass by the reaction e^+e^- -> W^+W^- with longitudinally polarized electrons. We perform a model-independent analysis of the deviations from the Standard Model, and apply it to a specific class of extended weak gauge models. Results indicate that the corresponding bounds at the NLC500 complement the present ones obtained from LEP1, and rapidly become quite stringent at the higher energy of the NLC1000. Also, we emphasize the importance of initial beam polarization in improving the sensitivity to mixing.

Abstract:
We explore the possibility of deriving model independent limits on the anomalous trilinear electroweak gauge boson couplings from high energy $e^+e^-\to W^+W^-$, by combining the cross sections for the different initial and final states polarizations integrated with suitable kinematical cuts. In the case of the CP conserving couplings the limits can be disentangled, and are given by simple mathematical expressions. Numerical results show the advantages of this approach, in particular the important role of polarization in improving the bounds.

Abstract:
Using a current algebra framework, we discuss the contribution of vector meson exchanges to the CP violating asymmetry in the decay $K^{\pm}\rightarrow\pi^{\pm}\pi^0$, resulting from the interference of the $K\rightarrow\pi\pi$ amplitude with the radiative correction $K\rightarrow\pi\pi\gamma$.

Abstract:
By means of a model-independent analysis, we discuss the constraints on anomalous trilinear gauge-boson couplings that can be obtained from the study of electron-positron annihilation into $W$ pairs at LC with \sqrt{s}=0.5 TeV and 1 TeV. We consider the general CP conserving anomalous effective Lagrangian, as well as some specific models with reduced number of independent couplings. The analysis is based on combinations of observables with initial and final state polarizations, that allow to separately constrain the different couplings and to improve the corresponding numerical bounds.

Abstract:
We quantitatively discuss the possibility of deriving model-independent constraints on the general four-fermion contact interaction couplings, from the currently available data on the two-fermion production processes $e^+e^-\to\mu^+\mu^-$, $b\bar{b}$ and $c\bar{c}$ with unpolarized initial beams. The method is essentially based on particular, simple, combinations of the measured total cross section and forward-backward asymmetry that allow partial separation of the helicity cross sections, and the combination of experimental data obtained at the different energies of TRISTAN, LEP1 and LEP2.

Abstract:
Fermion compositeness, and other types of new physics that can be described by the exchange of very massive particles, can manifest themselves as the result of an effective four-fermion contact interaction. In the case of the processes $e^+e^-\to \mu^+\mu^-,\tau^+\tau^-,\bar{b}b$ and $\bar{c}c$ at future $e^+e^-$ colliders with $\sqrt{s}=0.5-1$ TeV, we examine the sensitivity to four-fermion contact interactions of two new integrated observables, $\sigma_+$ and $\sigma_-$, conveniently defined for such kind of analysis. We find that, if longitudinal polarization of the electron beam were available, these observables would offer the opportunity to separate the helicity cross sections and, in this way, to derive model-independent bounds on the relevant parameters.