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Register a new userUpdated Status of the Global Electroweak Fit and Constraints on New Physics
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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.
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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 results 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.
In this presentation Gfitter results from the global Standard Model (SM) fit to electroweak precision data are discussed. We have used the latest measurements of m_top and M_W and the most recent results for direct Higgs searches at LEP and Tevatron. We obtain M_H=121^{+17}_{-6} GeV and a 95% CL upper limit of 155 GeV for the SM Higgs mass. The forth-order result for the strong coupling constant is given by alpha_S(M_Z^2)=0.1193 +- 0.0028(exp) +- 0.0001(theo). In addition the electroweak fit has been performed with the top mass determined from the ttbar cross-section as measured at Tevatron.
This letter summarises the status of the global fit of the CKM parameters within the Standard Model performed by the CKMfitter group. Special attention is paid to the inputs for the CKM angles $alpha$ and $gamma$ and the status of $B_stomumu$ and $B_dto mumu$ decays. We illustrate the current situation for other unitarity triangles. We also discuss the constraints on generic $Delta F=2$ New Physics. All results have been obtained with the CKMfitter analysis package, featuring the frequentist statistical approach and using Rfit to handle theoretical uncertainties.
We present updated global fits of the Standard Model and beyond to electroweak precision data, taking into account recent progress in theoretical calculations and experimental measurements. From the fits, we derive model-independent constraints on new physics by introducing oblique and epsilon parameters, and modified $Zbbar{b}$ and $HVV$ couplings. Furthermore, we also perform fits of the scale factors of the Higgs-boson couplings to observed signal strengths of the Higgs boson.
For a long time, global fits of the electroweak sector of the Standard Model (SM) have been used to exploit measurements of electroweak precision observables at lepton colliders (LEP, SLC), together with measurements at hadron colliders (Tevatron, LHC), and accurate theoretical predictions at multi-loop level, to constrain free parameters of the SM, such as the Higgs and top masses. Today, all fundamental SM parameters entering these fits are experimentally determined, including information on the Higgs couplings, and the global fits are used as powerful tools to assess the validity of the theory and to constrain scenarios for new physics. Future measurements at the Large Hadron Collider (LHC) and the International Linear Collider (ILC) promise to improve the experimental precision of key observables used in the fits. This paper presents updated electroweak fit results using newest NNLO theoretical predictions, and prospects for the LHC and ILC. The impact of experimental and theoretical uncertainties is analysed in detail. We compare constraints from the electroweak fit on the Higgs couplings with direct LHC measurements, and examine present and future prospects of these constraints using a model with modified couplings of the Higgs boson to fermions and bosons.
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