Luminosity is a measure for the collision rate in a particle accelerator experiment. The larger the instantaneous luminosity, the higher are the event rates in the detector. To make a precision measurement of a cross section of some process, a precise knowledge of the integrated luminosity is thus needed. At the CMS experiment, the luminosity measurement is calibrated with the Van der Meer method. A set of different subdetectors is used to integrate the measured instantaneous luminosity over a run period. By performing dedicated studies of various systematic effects, the CMS experiment is able to report its integrated luminosity with a very high precision.
