Patrick Janot edited Z partial widths and peak cross section.tex  over 10 years ago

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with a systematic uncertainty of 0.007. The experimental uncertainty was dominated by the statistics of leptonic decays, and other uncertainties related to the event selection will tend to decrease with statistics. The remaining systematic uncertainty were related to the $t$-channel contribution in the electron channel (which would vanish by the sole use of the muon channel) and to the detailed modelling of final-state radiation or emission of additional lepton pairs. Here, theory should be considerably helped by the large sample of leptonic Z decays available for the study of these rare processes. \\   {\em A relative precision of less than $10^{-5}$ is considered to be a reasonable target for the ratio of the Z hadronic-to-leptonic partial widths at TLEP}.\\  The precision measurements of the partical withs into electron, muon and tau pairs will also allow tests of the lepton universality in Z decays with considerably improved precision compared to the $3 \times  10^{-3}$ inferred from the LEP data. It is reasonable to consider that the TLEP statistics will allow lepton universality to be probed at the $10^{-5}$ level. \subsubsection{The peak hadronic cross section and the number of neutrinos}