Auxiliary material for the 2018 luminosity measurement

To use the calibration obtained from a van der Meer scan under physics data-taking conditions with more bunches and significantly higher instantaneous luminosity, an additional measurement of the stability and nonlinearity of the luminosity detectors is required. Potential nonlinear effects are important especially during Run 2 (2015-2018), where pileup during physics data taking reached up to about 50. CMS features luminosity subdetectors capable of providing real-time luminosity on a bunch-by-bunch level independently of the main CMS data acquisition system: the Fast Beam Conditions Monitor (BCM1F), the hadronic forward calorimeter (HF), and the Pixel Luminosity Telescope (PLT). Comparisons with further offline measurements using the pixel cluster counting (PCC) method and the radiation monitoring system (RAMSES) are presented.