Radiative corrections toW,Zmasses and constraints on newZbosons

We explore the implications of the recent $W$- and $Z$-boson-mass measurements at the SLAC Linear Collider, CERN LEP, and Fermilab Tevatron, and also the $\mu$ pair and total hadronic cross sections measured at KEK TRISTAN. A detailed comparison is made between the $M_W$ and $M_Z$ data and standard-model predictions including radiative corrections. These measurements also constrain extended electroweak gauge models. We place model-dependent upper bounds on the mass of a second neutral gauge boson from $M_W$ and $M_Z$ data, and set lower bounds on the $Z^{\prime }$ mass from direct production searches at the Collider Detector at Fermilab (CDF). We analyze the effects of $Z-Z^{\prime }$ mixing on the $Z$ width, leptonic branching ratio, and peak cross section at $e^{+}{e}^{-}$ colliders. We find that a second $Z$ cannot account for the increase in total hadronic and decrease in $\mu$-pair cross sections observed at KEK TRISTAN and simultaneously satisfy the CDF $Z^{\prime }$ search limits.