Patrick Janot edited 13311371548174299.tex  over 10 years ago

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These luminosity values are obtained in a configuration of the collider with four interaction points, for which the beam-beam parameters can be obtained directly from measurements performed at LEP1 and LEP2 in the 90's. For this reason, the instantaneous luminosity summed over the four interaction points, the only relevant quantity when it comes to evaluate the physics potential, is also shown in Fig.~\ref{fig:lumi}. Should TLEP operate with less detectors, the smaller beam-beam effects would tend to increase the instantaneous luminosity at each interaction point by a factor $(4/n_{\rm IP})^{0.4}$~\cite{Assmann:453821}. As a consequence, the use of two detectors instead of four would only reduce the total instantaneous luminosity by 35\% (as opposed to a naive factor 2 reduction), hence would increase the statistical uncertainties reported in the note by about 20\%. Although there is some debate as to the functional dependence of the beam-beam parameter on the damping decrement, any modifications to the the formula of Ref.~\cite{Assmann:453821} will have tiny effects on the conclusions of this analysis.