The factorization bias in the Van der Meer method: Run 2 experiences at the CMS experiment

Abstract

The luminosity measurement of the CMS experiment at the CERN LHC is calibrated with Van der Meer (VdM) scans. A bias occurs in the VdM method due to the assumption of transversely factorizable proton densities of the LHC beams. Here, the different methods applied in Run 2 to estimate the size of the factorization bias are reported. The beam-imaging method reconstructs the transverse proton densities from beam-imaging scans. Additional methods exploit offset scans, analyze the evolution of the measured luminous region, and evaluate diagonal scans.

arXiv commentPresented at the LHC Lumi Days 2019, Prévessin, France, June 04-05, 2019