Patrick Janot edited Luminosity measurement.tex  over 10 years ago

Commit id: 5d87d31bd6278e29b71ca23ebdde228b67a7ce65

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\begin{itemize}  \item The smaller value of $\beta^*_y$~\cite{cite:1305.6498} increases the beam divergence at the interaction point to the extent that it may have a sizeable effect on the acceptance of low angle detectors used for the luminosity measurement. The better stability of the TLEP beams will help to keep the uncertainty on the beam divergence to a level similar to that evaluated at LEP.   \item The strong final-focus quadrupoles will generate large amounts of synchrotron radiation, which need to be simulated and against which appropriate shielding must be provided.   \item An increased amount of beamstrahlung may lead to a somewhat larger background of electromagnetic radiation produced in the interaction region. As mentioned in Section~\ref{sec:beamstrahlung}, it is however nevertheless  several orders of magnitude smaller than the level expected in a linear collider environment. \item The repetition rate in multi-bunch operations will reach 20 MHz at the Z pole. This specificity has to be taken into account in the design of the detectors.   \end{itemize}  To the extent that the aforementioned issues are properly addressed and solved, there should be no significant difficulty to achieve luminosity measurements with an experimental precision similar to that obtained at LEP, typically a few times $10^{-4}$. At the Z peak it would be of interest, interest to achieve even better precision,  e.g., for the measurement of the invisible width, width  hence the number of light neutrinos,to achieve even better precision,  which will require a more precise construction of the luminometers. The main limitation on the luminosity measurement, however, would presently  comein the state of the art  from the theoretical calculation of the low angle Bhabha cross section. Clearly, progress in this aspect would pay great dividends.