During LHC Run 2 (2015-2018) the ATLAS Level-1 topological triggerallowed efficient data-taking by the ATLAS experiment at luminosities upto 2.1 x10(34) cm(-2) s(-1), which exceeds the design value by a factorof two. The system was installed in 2016 and operated in 2017 and 2018.It uses Field Programmable Gate Array processors to select interestingevents by placing kinematic and angular requirements on electromagneticclusters, jets, tau-leptons, muons and the missing transverse energy. Itallowed to significantly improve the background event rejection andsignal event acceptance, in particular for Higgs and B-physicsprocesses.

Performance of the ATLAS Level-1 topological trigger in Run 2

Capua, M.;Liu, X.;Liu, Y.;Maccarrone, G.;Mastroberardino, A.;Meoni, E.;