Patrick Janot edited EWSB parameters.tex  almost 11 years ago

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\section{\ref{sec:EWSB} Precise Measurements of the EWSB parameters}  \label{sec:EWSB}  Electroweak loops have the remarkable properties to be sensitive to the existence of weakly coupled particles even if they cannot be directly produced or observed in current experiments. For instance, the measurements of the Z resonance line shape undertaken at LEP during a dedicated scan in 1993 led to a prediction of the top quark mass of $m_{top}=179\pm 20$ GeV/$c^2$ by the time of the Moriond conference in March 1994, where the error represented largely a range of assumptions on the Higgs boson width. Once the top quark was measured at the Tevatron, the Electroweak fits were able to predict the only remaining unknown quantity in the Standard Model, the Higgs boson mass, to be in the range $m_H$ = 99 +28-23 GeV/$c^2$ \cite{PDG2012}. \cite{doi:10.1103/PhysRevD.86.010001}.  It is remarkable that the observation of the H(126) particle falls within one standard deviation of the prediction. It should be emphasized that these two remarkable predictions are specific of the Standard Model with its precise particle content -- and nothing else. They rule out the existence of any particle that would significantly contribute to the SM relationships between the so called Electroweak observables.