Trigger and data acquisition: The bytes start and stop here!

The modern trigger and data acquisition systems that instrument discovery experiments at the Large Hadron Collider (LHC) at CERN are very complex digital systems that select, reduce, and process enormous volumes of data in real-time to match the resources of state-of-the-art distributed computing available to researchers. Never before in particle physics have such powerful digital reconstruction and filtering systems been matched to a world-wide distributed system of computing of unprecedented scale. The goal of these massive aggregate computing systems is to extract as much physical information as possible from collision events at the LHC with well understood selection criteria and biases. Current strategies and future challenges in providing these aggregate real-time and offline computing systems are described. (C) 2010 Elsevier B.V. All rights reserved.