Critical Review of The Electroweak Precision Tests

Abstract

There have been a great deal of works on the precision test of the standard model (SM) because of the incredibly precise data obtained at the LEP and the new measurements of $M_W$ and $m_t$ at the Fermilab Tevatron as well as the recent theoretical progress in the higher order radiative corrections. We will discuss some of the hidden inputs and theoretical uncertainties involved in making the predictions of the observables in the SM. From the minimal $\chi^2$-fit to the experimental Z-decay parameters (with the aid of a modified ZFITTER program) in a scheme where $M_Z$, $G_{\mu}$ and $\alpha (M_Z)$ are taken as inputs, we can predict $M_W$ for given values of $m_H$ and $m_t$. The current world average value of $M_W$ definitely favor nonvanishing electroweak radiative corrections and is consistent with a heavy $m_t$ as measured by the recent CDF report but with a heavy Higgs scalar of about 500 GeV within the context of the minimal SM. The sensitivity of and the errors in the best fit solutions due to the uncertainties in the gluonic coupling $\alpha_s(M_Z)$ and $\alpha (M_Z)$ are examined carefully and any trace of new physics beyond the SM implied by the data, in a particular $R_b$ and $R_c$, is also touched upon. In addition we discuss how the future precision measurements of $M_W$ and $Z$ decay parameters can determine the Higgs boson mass and distinguish the SM with radiative corrections from the minimal supersymmetric standard model (MSSM) and other extended model.