\subsection{Measurements with TeraZ}

With a continuous luminosity of $5.6\times 10^{35}~\cms$ per IP at a centre-of-mass energy of 91 GeV, TLEP is a Z factory able to deliver over $20~\inab$ of data, i.e., $7\times 10^{11}$ visible Z decays for one year of running (hence the ``Tera Z'' appellation), with very clean experimental conditions, centre-of-mass energy known to a fraction of MeV, and the possibility of longitudinally polarized beams, with which the following experiments can be carried out: 
\begin{itemize}
\item a high-statistics line-shape scan of the Z resonance, allowing an extremely precise determination of the Z mass and width;
\item high-statistics data collection at the Z peak, for the measurement of the Z partial widths, the determination of the number of light neutrinos, and the detection of rare decays;
\item high-statistics data taking with longitudinally-polarized beams, for a very precise determination of the weak mixing angle.
\end{itemize}
An extensive description of Electroweak measurements performed at LEP and SLC in 1988-1998 can be found in Ref.~\cite{ements_on_the_Z_resonance_2006}. It is beyond the scope of this article to revisit all the measurements in view of establishing the improvements potentially brought about by TLEP. Only a brief account of a few key measurements is given here. Typically, TLEP will bring a factor $10^5$ to the statistics accumulated at LEP, which corresponds to statistical uncertainties reduced by a factor 300. With such a huge improvement, it is clear that a detailed consideration of experimental systematic uncertainties will be essential before a precise conclusion be drawn on the ultimately achievable precisions. Above all, uncertainties in the theoretical interpretation will need to be revisited, which implies a significant new programme of calculations of higher-order Electroweak corrections. 




 


