The ATLAS Trigger Core Configuration and Execution System in Light of the ATLAS Upgrade for LHC Run 2

During the 2013/14 shutdown of the Large Hadron Collider (LHC) the ATLAS first level trigger (L1) and the data acquisition system (DAQ) were substantially upgraded to cope with the increase in luminosity and collision multiplicity, expected to be delivered by the LHC in 2015. Upgrades were performed at both the L1 stage and the single combined subsequent high level trigger (HLT) stage that has been introduced to replace the two-tiered HLT stage used in Run 1. Because of these changes, the HLT execution framework and the trigger configuration system had to be upgraded. Also, tools and data content were adapted to the new ATLAS analysis model.