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Seesaw models with a small lepton number breaking can naturally accommodate electroweak-scale pseudo-Dirac neutrinos with a sizable mixing with the active neutrinos, while satisfying the light neutrino oscillation data. Due to the smallness…
The most reliable prediction for the Higgs-boson mass, M_H, is obtained in a fit to the leptonic Z-resonance observables Gamma_l and swbar^2 combined with the W-boson mass, M_W, and top-quark mass, m_t, measurements. The corresponding…
The latest results of Higgs boson searches from the four LEP experiments, ALEPH, DELPHI, L3 and OPAL, are reviewed using the data taken in 1996 at center-of-mass energies between 161 and 172 GeV. No signal was observed. The 95% CL combined…
The universality of free fall, the weak equivalence principle (WEP), is a cornerstone of the general theory of relativity, the most precise theory of gravity confirmed in all experiments up to date. The WEP states the equivalence of the…
Motivated by the recent precision measurements of the W boson mass and top quark mass, we test the Littlest Higgs model by confronting the prediction of M_W with the current and prospective measurements of M_W and M_t as well as through the…
The last years have seen a great development in our understanding of particle physics at the weak scale. Precision electroweak observables have played a key role in this process and their values are consistent, within the Standard Model…
1. Introduction 2. Status of the Data 3. Precision Electroweak Data and the Standard Model 4. A More General Analysis of Electroweak Data 4.1 Basic Definitions and Results 4.2 Experimental Determination of the Epsilon Variables 4.3…
We obtain mass limits on the extra neutral gauge boson which is predicted in a model with hidden gauge symmetry and dynamical breaking of the electroweak symmetry by a top quark condensate. For typical model assumptions, present LEP data…
We quantify the amount of fine tuning of input parameters of the Minimal Supersymmetric Extension of the Standard Model (MSSM) that is needed to respect the lower limits on sparticle and Higgs masses imposed by precision electroweak…
We show how the spectrum of the minimal anomaly-mediated supersymmetry breaking model can be constrained from the condition that the electroweak symmetry breaking minimum of the scalar potential is the deepest point in the field space.…
Indirect limits on the mass of the lightest neutralino are derived from the results of searches for charginos, neutralinos, and sleptons performed with data taken by the ALEPH Collaboration at centre-of-mass energies near the Z peak and at…
The existence of extra chiral generations with all fermions heavier than $M_Z$ is strongly disfavored by the precision electroweak data. The exclusion of one additional generation of heavy fermions in SUSY extension of Standard Model is…
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…
We have performed a detailed Monte Carlo exploration of the parameter space for a warped Higgsless model of electroweak symmetry breaking in 5 dimensions. This model is based on the $SU(2)_L\times SU(2)_R\times U(1)_{B-L}$ gauge group in an…
The global electroweak fit of the Standard Model (SM) with Gfitter can be used to constrain yet unknown SM parameters, such as the Higgs mass, but also physics beyond the SM (BSM) via the formalism of oblique parameters. This paper presents…
We discuss the sensitivities of present-day electroweak precision data to the possible scale of supersymmetry within the constrained minimal supersymmetric extension of the Standard Model (CMSSM). Our analysis is based on M_W, sin^2…
We perform an analysis of the electroweak precision observables in the Lee-Wick Standard Model. The most stringent restrictions come from the S and T parameters that receive important tree level and one loop contributions. In general the…
In this paper we express the effect of new physics on gauge boson self energy corrections through non-renormalizable dimension six operators. Using the precision electroweak data we then determine a lower bound on the scale ${\l}$…
We study the electroweak interactions within the standard electroweak theory in the case where the Higgs particle is heavy, namely, $M_H \leq 1\;TeV$. By integrating out the Higgs boson to one loop we find the complete effective lagrangian,…
A search for charginos and neutralinos, predicted by supersymmetric theories, has been performed using a data sample of 57 pb-1 at centre-of-mass energies of 181-184 GeV taken with the OPAL detector at LEP. No evidence for chargino or…