The Electroweak Fit of the Standard Model after the Discovery of a New Boson at the LHC The Gfitter Group

Abstract — In view of the discovery of a new boson by the ATLAS and CMS Collaborations at the LHC, we present an update of the global Standard Model (SM) fit to electroweak precision data. Assuming the new particle to be the SM Higgs boson, all fundamental parameters of the SM are known allowing, for the first time, to overconstrain the SM at the electroweak scale and assert its validity. Including the effects of radiative corrections and the experimental and theoretical uncertainties, the global fit exhibits a p-value of 0.07. The mass measurements by ATLAS and CMS agree within 1.3σ with the indirect determination MH = 94 +25 −22 GeV. Within the SM the W boson mass and the effective weak mixing angle can be accurately predicted to be MW = 80.359±0.011GeV and sin2θ`eff = 0.23150±0.00010 from the global fit. These results are compatible with, and exceed in precision, the direct measurements. For the indirect determination of the top quark mass we find mt = 175.8 +2.7 −2.4 GeV, in agreement with the kinematic and cross-section based measurements. ar X i