Triggering on hadronic signatures in ATLAS: developments for 2017 and 2018 data

The ATLAS trigger system is tasked with selecting the roughly 1000 most interesting events out of the up to 40 million LHC bunch crossings that occur every second during data-taking. Triggers aimed at hadronic physics, which are responsible for selecting events containing jets, $b$-jets, and missing transverse momentum, have received significant algorithmic improvements in preparation for the 2017 and 2018 data-taking periods. These changes have been made to account for the continuously changing LHC beam conditions, and particularly for the the average number of simultaneous $pp$ collisions per bunch crossing, which is increasing every year and which poses a significant challenge for hadronic triggers. These hadronic trigger developments have allowed the ATLAS trigger system to both continue to operate in increasingly difficult conditions and to increase the diversity of the recorded events, therefore supporting and extending the ATLAS physics program.