Luminosity measurement in the interaction regions of the LHC using proton–proton collision multiplicities

Described in this article is a new method for determining the absolute proton luminosity at the Large Hadron Collider. The method is based on counting the number of inelastic proton–proton interactions in a bunch crossing. We show that this should be possible using the inner detector systems of the ATLAS and CMS experiments. Dedicated luminosity instrumentation is not required. The method is best suited for the initial low luminosity phase of the LHC, but its application at high luminosity is also considered.