ATLAS Pile-up and Overlay Simulation
T. Novák · CERN Document Server (European Organization for Nuclear Research) · 2017
The high luminosity of the LHC results in a significant background to interesting physics events known as pile-up. ATLAS uses several methods for simulating the effects of pile-up. The mostly used method is a direct simulation of background events where multiple simulated background events are combined for each physics event. For some physics processes, a more accurate simulation can be achieved by overlaying real proton-proton collisions on a simulated hard-scatter process. Overlay is also being investigated for a premixed pile-up background to reduce CPU usage and I/O stress during the simulation. Embedding replaces the muons found in Z→mumu decays in data with simulated taus at the same 4-momenta, thus preserving the underlying event and pileup from the original data event. This talk compares the pile-up simulation methods used at the ATLAS experiment pointing their benefits and drawbacks.