An Implementation of Region-of-Interest Selection for ATLAS High Level Trigger and Offline Software Environments

Among the many challenges presented by the future ATLAS detector and LHC accelerator are the high data taking rate and volume and the derivation of a rapid trigger decision within limited computing and networking resources. To address this challenge, within the High Level Trigger (HLT) system, a novel Region-of-Interest (RoI) mechanism is used which dramatically reduces the relevant fiducial volume necessary to be readout and processed to small regions guided by the hardware-based first level trigger.