Methods To Quantify The Performance Of The Primary Vertex Reconstruction In The Atlas Experiment Under High Luminosity Conditions

Presented in this contribution are methods currently developed and used by the ATLAS collaboration to measure the performance of the primary vertex reconstruction algorithms. These methods quantify the amount of additional pile up interactions and help to identify the hard scattering process (the so called primary vertex) in the proton-proton collisions with high accuracy. The correct identification of the primary vertex and knowledge of the amount of pile up per bunch crossing is crucial for many physics analyses. With the increasing instantaneous luminosity at the LHC additional effects like splitting one vertex into many or reconstructing several pile up interactions as one become sizable effects. Statistical methods based on data and Monte Carlo simulation are applied to disentangle the different contributions. The mathematical methods, their software implementation and comparisons with independent luminosity measurements are presented.