Related papers: Heavy fermions virtual effects at e^+ e^- collider…
We derive the low-energy electroweak effective lagrangian for the case of additional heavy, unmixed, sequential fermions. Present data still allow for the presence of a new quark and/or lepton doublet with masses greater than $M_Z/2$,…
We analyse the contribution of new heavy virtual fermions to the $e^+e^- \rightarrow W^+W^-$ cross section. We find that there exists a relevant interplay between trilinear and bilinear oblique corrections. The result strongly depends on…
We extend our previous work on non-linear realization of the top quark field, which is a consequence of its being much heavier than any other scales. One loop effective Lagrangian to account for virtual top effects is constructed in this…
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 perform a global analysis of the sensitivity of LEP2 and e^+e^- colliders with a c.m. energy in the range 500 - 2000 GeV to new flavor-changing single top quark production in the effective Lagrangian approach. The processes considered…
It is possible to place direct constraints on WW-photon and WWZ couplings by studying their tree-level contributions to the process e^+e^- ---> W^+W^-. However, these couplings also contribute at the loop level to e^+e^- ---> f fbar…
In this paper we consider a general $SU(2)_L\otimes SU(2)_R$ invariant Lagrangian describing scalar, vector and axial-vector resonances. By expanding the WW and the ZZ scattering amplitude up to the fourth order in the external momenta we…
A fermion can be chiral or vectorlike with respect to a given symmetry, depending on its coupling to the corresponding gauge boson. Vectorlike fermions have a distinct property that their left-handed and right-handed components behave in…
We discuss the sensitivity of the $e^+ e^- \rightarrow W^+ W^-$ cross section at a future $e^+ e^-$ collider with $\sqrt{s}=500$GeV to the non-decoupling effects of a techni-$\rho$ like vector resonance. The non-decoupling effects are…
Possible oblique effects from vector particles that are strongly coupled to the known gauge bosons are calculated for the case of final hadronic states produced at future $e^+e^-$ colliders, using a formalism that was recently proposed and…
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^-…
We study large top quark mass effects on low energy physics in the chiral Lagrangian formulated electroweak theories. We show that these radiative corrections can be easily obtained from a set of Feynman diagrams involving only the scalar…
We perform a comparative study of the reach of future $e^+e^-$ collider options for the scale of non-resonant new physics effects in the top quark sector, phrased in the language of higher-dimensional operators. Our focus is on the…
The virtual massive gauge boson effects on several observables in the process of charged fermion pairs production at $e^+e^-$ colliders are computed up to the TeV energy range in the Standard Model, working in the ``$Z$-peak subtracted''…
We examine two processes, the neutrino production process e^+e^- ---> N\nu and the inverse neutrinoless double-beta decay process e^-e^- --->W^-W^- as possible places for discovering heavy neutrinos in future lepton linear colliders. The…
We explore the effects of a heavy fermion doublet in a simplified version of the standard electroweak theory. We integrate out the doublet and compute the exact effective energy functional of spatially varying gauge and Higgs fields. We…
We update the uncertainty analysis on $S$ parameter of the electroweak chiral Lagrangian (EWCL) by including the LEP-II W pair production data. We find that experimental data still allow a positive $S^{EXP}(1\textrm{TeV})$.
The production of four fermions plus a visible photon in electron-positron collisions is analyzed, with particular emphasis on the LEP2 energy range. The study is based on the calculation of exact matrix elements, including the effect of…
We consider the virtual effects of a general type of Anomalous (triple) Gauge Couplings on various experimental observables in the process of electron-positron annihilation into a final fermion-antifermion state. We show that the use of a…
We study the diagnostic power of future $e^+e^-$ colliders with ${\sqrt {s}} = 500$ GeV (the New Large Collider ($NLC$)) for a model independent determination of the $Z'$ gauge couplings to quarks and leptons. The interference of the $Z'$…