Çetin, Serkant Ali2022-10-072022-10-072022-122510-2044https://hdl.handle.net/11411/4555https://doi.org/10.1007/s41781-021-00062-2Abstract: he accurate simulation of additional interactions at the ATLAS experiment for the analysis of proton– proton collisions delivered by the Large Hadron Collider presents a significant challenge to the computing resources. During the LHC Run 2 (2015–2018), there were up to 70 inelastic interactions per bunch crossing, which need to be accounted for in Monte Carlo (MC) production. In this document, a new method to account for these additional interactions in the simulation chain is described. Instead of sampling the inelastic interactions and adding their energy deposits to a hard-scatter interaction one-by-one, the inelastic interactions are presampled, independent of the hard scatter, and stored as combined events. Consequently, for each hard-scatter interaction, only one such presampled event needs to be added as part of the simulation chain. For the Run 2 simulation chain, with an average of 35 interactions per bunch crossing, this new method provides a substantial reduction in MC production CPU needs of around 20%, while reproducing the properties of the reconstructed quantities relevant for physics analyses with good accuracyeninfo:eu-repo/semantics/openAccessArticle2-s2.0-8512427633510.1007/s41781-021-00062-2Q1