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

Understand

During LHC Run 2 (2015-2018) the ATLAS Level-1 topological trigger allowed efficient data-taking by the ATLAS experiment at luminosities up to 2.1x10$^{34}$ cm$^{-2}$s$^{-1}$, which exceeds the design value by a factor of two.

• The system was installed in 2016 and operated in 2017 and 2018.
• It uses Field Programmable Gate Array processors to select interesting events by placing kinematic and angular requirements on electromagnetic clusters, jets, $\tau$-leptons, muons and the total energy.
• It significantly improves the background event rejection and signal event acceptance, in particular for Higgs boson and $B$-physics measurements.