Aad, G.Abbott, B.Abbott, D. C.Abed Abud, A.Abeling, K.Abhayasinghe, D. K.Çetin, Serkant Ali2024-07-182024-07-1820211434-60441434-6052https://doi.org/10.1140/epjc/s10052-021-09775-5https://hdl.handle.net/11411/7920Several improvements to the ATLAS triggers used to identify jets containing b-hadrons (b-jets) were implemented for data-taking during Run 2 of the Large Hadron Collider from 2016 to 2018. These changes include reconfiguring the b-jet trigger software to improve primary-vertex finding and allow more stable running in conditions with high pile-up, and the implementation of the functionality needed to run sophisticated taggers used by the offline reconstruction in an online environment. These improvements yielded an order of magnitude better light-flavour jet rejection for the same b-jet identification efficiency compared to the performance in Run 1 (2011-2012). The efficiency to identify b-jets in the trigger, and the conditional efficiency for b-jets that satisfy offline b-tagging requirements to pass the trigger are also measured. Correction factors are derived to calibrate the b-tagging efficiency in simulation to match that observed in data. The associated systematic uncertainties are substantially smaller than in previous measurements. In addition, b-jet triggers were operated for the first time during heavy-ion data-taking, using dedicated triggers that were developed to identify semileptonic b-hadron decays by selecting events with geometrically overlapping muons and jets.eninfo:eu-repo/semantics/openAccessPair ProductionPlus PlusTrackArticle2-s2.0-8512095875210.1140/epjc/s10052-021-09775-512Q181Q2WOS:000728553000002