Journal of High Energy Physics

, 2019:225 | Cite as

Beam-beam effects on the luminosity measurement at FCC-ee

  • Georgios Voutsinas
  • Emmanuel Perez
  • Mogens Dam
  • Patrick JanotEmail author
Open Access
Regular Article - Experimental Physics


The first part of the physics programme of the integrated FCC (Future Circular Colliders) proposal includes measurements of Standard Model processes in e+e collisions (FCC-ee) with an unprecedented precision. In particular, the potential precision of the Z lineshape determination calls for a very precise measurement of the absolute luminosity, at the level of 104, and the precision on the relative luminosity between energy scan points around the Z pole should be an order of magnitude better. The luminosity is principally determined from the rate of low-angle Bhabha interactions, e+e e+e, where the final state electrons and positrons are detected in dedicated calorimeters covering small angles from the outgoing beam directions. Electromagnetic effects caused by the very large charge density of the beam bunches affect the effective acceptance of these luminometers in a nontrivial way. If not corrected for, these effects would lead, at the Z pole, to a systematic bias of the measured luminosity that is more than one order of magnitude larger than the desired precision. In this note, these effects are studied in detail, and methods to measure and correct for them are proposed.


e+-e- Experiments Electroweak interaction 


Open Access

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Copyright information

© The Author(s) 2019

Authors and Affiliations

  1. 1.CERN, EP DepartmentMeyrinSwitzerland
  2. 2.Niels Bohr InstituteUniversity of CopenhagenCopenhagenDenmark

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