deletions | additions       diff --git a/Measurements at the WW threshold.tex b/Measurements at the WW threshold.tex  index e3c083b..9141a89 100644  --- a/Measurements at the WW threshold.tex  +++ b/Measurements at the WW threshold.tex 
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With an integrated luminosity of the order of 1.6 ab$^{-1}$ per year and per experiment TLEP-W will be a W factory as well. We concentrate here on one single, flagship, measurement: the W boson mass.   The safest and most sensitive measurement of the W mass can be performed at threshold. At LEP~\cite{LEP-2} this was done at a unique center of mass energy of 161.3 GeV. A more thorough scan, including a point below threshold for calibration of possible backgrounds, should probably be envisaged to provide the redundancy necessary for a precise measurement. The measurement is essentially statistics dominated and the only relevant uncertainties are those associated with the definition of the center-of-mass energy as described in the relevant section above. Taking as starting point the precision achieved at LEP, a statistical error of 1 MeV on the W mass should be achievable (0.5 MeV for the four experiments). Given that at TLEP the energy calibration from resonant depolarization will be available at least up to 81 GeV per beam, a possible scan should involve one or both of the two points situated close to the point of maximum $M_W$ sensitivity and situated at the half integer spin-tune,$\nu_s =$ 182.5 and 183.5, i.e. $E_{beam}=$ 80.4 and 80.85 GeV. It should be noted that TLEP is not sensitive to the correct understanding of the beam energy spread or of the beamstrahlung.  A more careful analysis may reveal systematic errors that are relevant at this level of precision, although they should be somewhat similar to those involved in the Z mass measurement from the line shape, i.e. dominated by the uncertainties on the initial state QED corrections and the theoretical parametrization of the W threshold, with threshold. With  the same logic as above we consider that these should be reducible to a level below 100 keV on $M_W$. \\  {\em We consider that 500 keV is a reasonable target goal for the W mass precision at TLEP-W}.