Luminosity scans for beam diagnostics

A new type of fast luminosity separation scans (emittance scans) was introduced at the CERN Large Hadron Collider (LHC) in 2015. The scans were performed systematically in every fill with full-intensity beams in physics production conditions at the interaction point (IP) of the compact muon solenoid (CMS) experiment. They provide both transverse emittance and closed orbit measurements at a bunch-by-bunch level. The precise measurement of beam-beam closed orbit differences allowed a direct, quantitative observation of long-range beam-beam PACMAN effects, which agrees well with numerical simulations from an improved version of the TRAIN code.