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 updated r
esults of the Gfitter SM fit using the latest available electroweak precision measurements and the recent combination of direct Higgs searches at the Tevatron. In addition, newly obtained constraints on BSM models, such as models with extra dimensions, little Higgs and a fourth fermion generation, are presented. While a light Higgs mass is preferred by the fit in the SM, significantly larger Higgs masses are allowed in these new physics models.
The global fit of the Standard Model to electroweak precision data, routinely performed by the LEP electroweak working groups and others, has been revisited in view of (i) the development of the new generic fitting package, Gfitter, (ii) the insertio
n of constraints from direct Higgs searches at LEP and Tevatron, and (iii) a more thorough statistical interpretation of the results. This paper describes the Gfitter project, and presents state-of-the-art results for the global electroweak fit in the Standard Model, and for a model with an extended Higgs sector. Example results are an estimation of the mass of the Higgs boson (M_H = 116.4^{+18.3}_{-1.3} GeV) and a forth-order result for the strong coupling strength (alpha_S(M_Z^2) = 0.1193^{+0.0028}_{-0.0027}(exp)+/-0.0001(theo)). Using toy Monte Carlo techniques the p-value of the SM has been determined (p=0.22). As an example of a New Physics model constraints are derived for the Two Higgs Doublet Model of Type-II using observables from the B and K physics sectors.
