Trigger systems of LHC experiments

Abstract

Interaction rates at CERN's Large Hadron Collider (LHC) increase with the collider's luminosity and collision energy. All LHC experiments and in particular their trigger systems have to take this fact into account in order to ensure efficient physics data taking while at the same time keeping data rates at an acceptable level. This paper presents an overview of the most important trigger upgrades that have happened since the end of LHC Run 1 in 2012, describes work currently underway and presents an outlook on major improvements planned for the medium-term future.