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

TL;DR

This paper reports on the successful implementation and operation of the ATLAS Level-1 topological trigger during LHC Run 2, which enhanced event selection efficiency at high luminosities, benefiting Higgs and B-physics studies.

Contribution

It presents the deployment and performance evaluation of a novel FPGA-based topological trigger system that improved event filtering at high luminosity in the ATLAS experiment.

Findings

Efficient data-taking at luminosities up to 2.1x10^{34} cm^{-2}s^{-1}

Significant improvement in background rejection and signal acceptance

Enhanced capabilities for Higgs and B-physics measurements

Abstract

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.