Related papers: LEP 2 e+e-->ffbar, gamma gamma (gamma): results an…
If high mass di-gamma events observed at LEP are due to the production of a di-gamma resonance via its leptonic coupling, its consequences can be observed at TRISTAN. We find that a predicted $Z$ decay branching rate is too small to account…
We present sensitivity limits on the coefficients of a dimension-6 effective Lagrangian that parametrizes the possible effects of new physics beyond the Standard Model. Our results are based on the study of the process $e^+ e^- \to W^+ W^-…
In terms of an effective lagrangian, we examine the effect of new physics associated with third-generation fermions on b b-bar production at the Z resonance and study its implications for LEP2. We obtain the constraints on such operators…
Using the laser backscattering method at future TeV linear colliders one can obtain gamma-gamma and electron-gamma colliding beams (photon colliders) with the energy and luminosity comparable to that in e+e- collisions. Now this option is…
Results on W-pair productions at LEP2 are reviewed and their consistency with standard electroweak expectations is summarised. Special interest is given to measurements of W polarisation, and to new studies of spin and decay-plane…
Contribution to LP99, International Symposium on Lepton-Photon Interactions, Stanford, Aug.1999. Summary of works done in collaboration with M. Beccaria, P. Ciafaloni, D. Comelli, G.J. Gounaris, J. Layssac, P. Porfyriadis, S. Spagnolo, C.…
We present complete analytical expressions for the amplitudes of the process $e\bar{e}\rightarrow H\gamma$. The calculation is performed using nonlinear gauges, which significantly simplifies both the actual analytical calculation and the…
The production of photon pairs in $e^+e^-\rightarrow f \bar f \gamma\gamma$ processes is studied using exact helicity amplitudes at tree level. Total cross sections, including initial state radiation effects, are given. They are presented…
Electroweak processes with four fermions in the final state were measured extensively at LEP-2 in e+e- collisions with centre-of-mass energies up to 209 GeV. By combining the results obtained by Aleph, Delphi, L3 and Opal, the predictions…
It has been shown in the past that the real part of the e'/e ratio is particularly sensitive to anomalous gauge couplings that modify the Standard Model Lagrangian. Due to the loose bounds on these couplings coming from low energy processes…
We discuss the production, at high--energy e$^+$e$^-$ linear colliders, of new heavy fermions predicted by extensions of the Standard Model. We analyze in great details the various signals and the corresponding backgrounds for both pair…
We investigate the effect of anomalous gamma-W-W couplings in e-gamma --> nu W through the angular and energy spectrum of the secondary leptons. Within the narrow-width approximation, a semi-analytical study of the secondary lepton…
In five years of operation (1996-2000) the four LEP2 experiments collected roughly 3 fb-1 of data from e+e- collisions at centre-of-mass energies between 161 and 207 GeV, yielding a total of about 40000 W-pair events. The analysis of the…
The processes $e^+e^-\to e^+e^-X$, with $X$ being either the $\eta$ meson or $\pi^0\pi^0$, are studied at DA$\Phi$NE, with $e^+e^-$ beams colliding at $\sqrt{s}\simeq1$ GeV, below the $\phi$ resonance peak. The data sample is from an…
The e+e- -> p anti-p cross section is determined over a range of p anti-p masses, from threshold to 4.5 GeV/c^2, by studying the e+e- -> p anti-p gamma process. The data set corresponds to an integrated luminosity of 232 fb^-1, collected…
We analyze various perturbative mechanisms for the production of jet events containing rapidity gaps in $e^+e^-$ annihilation at LEP200 energies. We found that the processes $e^+e^- \to \gamma^* \gamma^*, \gamma^* Z, Z Z, WW \to 4~ jets$…
Anomalous quartic couplings between the electroweak gauge bosons may contribute to the vv gamma gamma and qq gamma gamma final states produced in e+e- collisions. This analysis uses the LEP2 OPAL data sample at centre-of-mass energies up to…
We analyze the manifestations of new matter particles predicted by models of new physics beyond the Standard Model, at present and future high--energy colliders. We consider both the production of these new particles and some of their…
Ultra-high-energy, >10^19 eV, cosmic-ray and high energy, ~10^14 eV, neutrino production in GRBs is discussed in the light of recent GRB and cosmic-ray observations. Emphasis is put on model predictions that can be tested with operating and…
The possibility of single and pair excited neutrino production in high energy e+e-, gamma-e and gamma-gamma collisions on linear colliders is studied. The integrated cross sections of these subproceses are calculated. Special attention is…