Related papers: Extra generations and discrepancies of electroweak…
The 1999 precision electroweak data from LEP and SLC persist in showing some slight discrepancies from the assumed standard model, mostly regarding $b$ and $c$ quarks. We show how their mixing with exotic heavy quarks could result in a more…
We calculate the contributions to electroweak precision observables (EWPOs) due to a fourth generation of fermions with the most general (quark-)flavour structure (but assuming Dirac neutrinos and a trivial flavour structure in the lepton…
The Standard Model has three generations of fermions and although it does not contain any explicit reason for this, the existence of additional generations is now very constrained by experiment. Present measurements are saturating…
I review constraints on the Standard Model (SM) Higgs boson from high energy electroweak (EW) precision data. The same data set also strongly limits various mixing effects of hypothetical extra neutral gauge bosons (Z') with the ordinary Z.…
While it is known that third family hypercharge models can explain the neutral current $B-$anomalies, it was hitherto unclear whether the $Z-Z^\prime$ mixing predicted by such models could simultaneously fit electroweak precision…
In a generic 'universal' theory of electroweak symmetry breaking, non fine-tuned heavy new physics affects the low-energy data through four parameters, which include and properly extend the generally insufficient S and T. Only by adding the…
Direct constraints on the masses of new heavy bosons by the Tevatron data are discussed. Some excesses in the experimental data are interpreted as a resonance production of new charged and `leptophobic' neutral chiral bosons with masses…
Many types of physics beyond the standard model include an extended electroweak gauge group. If these extensions are associated with flavor symmetry breaking, the gauge interactions will not be flavor-universal. In this note we update the…
We review the empirical evidence for the validity of the Standard Electroweak Theory in Nature. The experimental data are interpreted in terms of an effective Lagrangian for Z physics, allowing for potential sources of SU(2) violation and…
The three generation mirror fermion model is compared with LEP precision and low energy data. While for zero mixing of ordinary and mirror fermions the model is not favoured, for non zero mixing very low $\chi ^2 $ fits have been obtained,…
A model for electroweak unification of quarks and leptons, in a gauge group $SU_{C}(3)\times SU(4)\times U_{X}(1)$ is constructed. The model requires, three generations of quarks and leptons which are replicas (mirror) of the standard…
Recent improvements to OPUCEM, the tool for calculation of the contributions of various models to oblique parameters, are presented. OPUCEM is used to calculate the available parameter space for the four family Standard Model given the…
New almost-degenerate charged and neutral heavy leptons are a feature of a number of theories of physics beyond the Standard Model. The prospects for detecting these at the Large Hadron Collider using a time-of-flight technique are…
We consider the bounds for the values of higgs mass $M_H$ and of the mass of the extra quarks and leptons $M_{extra}$ derived from the stability of vacuum and from the absence of Landau pole in Higgs potential. We find that in the case of…
The electroweak radiative correction, which turned out to be marginal within the standard electroweak model having the minimal Higgs sector in view of the present experimental information, fits well the experiment when the Higgs sector is…
Until recently precision electroweak computations were fundamentally uncertain due to lack of knowledge about the existence of the Standard Model Higgs boson and its mass. For this reason substantial calculational machinery had to be…
We present a new complete analysis of the electroweak precision observables within the recently proposed 4-site Higgsless model, which is based on the SU(2)_L x SU(2)_1 x SU(2)_2 x U(1)_Y gauge symmetry and predicts six extra gauge bosons,…
We propose a scheme in that the masses of the heavier leptons obey seesaw type relations. The light lepton masses, except the electron and the electron neutrino ones are generated by one loop level radiative corrections. We work in a…
The present status of precision electroweak data is reviewed. These data include measurements of e+e- -> f+fbar, taken at the Z resonance at LEP, which are used to determine the mass and width of the Z boson. In addition, measurements have…
Our picture of the electroweak interactions continues to improve, with ever more precise constraints on the masses of the Higgs boson(s) and on non-standard physics. Some recent developments include: (a) a calculation of higher-order…