Abstract
The Large Hadron Collider (LHC) provides proton-proton collisions with a nominal rate of 40 MHz, and the ATLAS trigger performs the first event selections online during data- taking. The ATLAS jet trigger is an important element of the ATLAS trigger system, selecting collision events containing high transverse energy jets, to provide data samples for studies ranging from Standard Model physics to searches for new physics at the LHC. During LHC Run I, the first LHC operation period from 2010 to 2012, the ATLAS jet trigger system improved as experience developed with triggering in a high luminosity and high event pileup environment. For the next LHC operation period, Run II, the system is being updated for further improved performance and stability. In this contribution, performance and improvements of the ATLAS jet trigger in Run I are presented. Updates for Run II are also shown.
Highlights
A jet is a collimated spray of hadrons
Overview of the ATLAS jet trigger system in Run I In Run I, the ATLAS trigger system consisted of three levels, Level 1 (L1), Level 2 (L2) and Event Filter (EF), where L1 was hardware-based and L2 and EF were software-based
The reconstructed jets at this layer are called L2 Full Scan (L2FS) jets. Both L2FS jets and L1 Region of Interest (RoI) could be used as inputs at L2 for further jet reconstruction with the cone algorithm using calorimeter cells
Summary
A jet is a collimated spray of hadrons. It is produced by a scattered quark or gluon with high transverse energy (ET ) and is an important signature in collider physics. It can perform reconstruction of anti-kt [3] jets (as implemented in the FastJet package [4]) using L1 calorimeter towers with a granularity of 0.1 × 0.1 in η × φ, across the entire ATLAS detector.
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