Abstract
We present an update of the Standard Model fit to electroweak precision data. We include newest experimental results on the top quark mass, the W mass and width, and the Higgs boson mass bounds from LEP, Tevatron and the LHC. We also include a new determination of the electromagnetic coupling strength at the Z pole. We find for the Higgs boson mass (91 +30 -23) GeV and (120 +12 -5) GeV when not including and including the direct Higgs searches, respectively. From the latter fit we indirectly determine the W mass to be (80.360 +0.014 -0.013) GeV. We exploit the data to determine experimental constraints on the oblique vacuum polarisation parameters, and confront these with predictions from the Standard Model (SM) and selected SM extensions. By fitting the oblique parameters to the electroweak data we derive allowed regions in the BSM parameter spaces. We revisit and consistently update these constraints for a fourth fourth fermion generation, two Higgs doublet, inert Higgs and littlest Higgs models, models with large, universal or warped extra dimensions and technicolour. In most of the models studied a heavy Higgs boson can be made compatible with the electroweak precision data.
Highlights
By exploiting contributions from radiative corrections, precision measurements, in line with accurate theoretical predictions, can be used to probe physics at higher energy scales than the masses of the particles directly involved in the experimental reactions
Assuming that the dominant virtual contributions to the electroweak observables arise through vacuum polarisation loops, and that other corrections, such as vertex diagrams involving light quarks, or box and bremsstrahlung diagrams, are scale suppressed, physics beyond the Standard Model (SM) (BSM) can be parametrised through so-called quantum oblique corrections, for which several parametrisations exist in the literature [5,6,7,8,9,10,11,12,13]
Extended technicolour models (ETC) have been developed to address this issue by assuming that ordinary SU (3) colour, SU (NTC) technicolour, and flavour symmetries are unified into one gauge group GETC, which allows the technifermions to couple to quarks and leptons via gauge bosons of the enlarged group
Summary
By exploiting contributions from radiative corrections, precision measurements, in line with accurate theoretical predictions, can be used to probe physics at higher energy scales than the masses of the particles directly involved in the experimental reactions. For cases where the parameter space is overconstrained it is possible to derive p-values for the compatibility between data and theoretical model [1], and to directly assess the validity of the model. Such an approach has been used in the Gfitter analysis of the Standard Model (SM) in light of the electroweak precision data [2], which we revisit in this paper with updated experimental constraints.
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