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Abstract
| The LHCb experiment is dedicated to the study of particles containing b or c quarks at the LHC. The LHCb trigger system plays a key role in selecting signal events and rejecting background. It consists of two stages: a hardware trigger followed by a high-level trigger implemented in software. The majority of the work is performed by the high level trigger. With its flexible design, the LHCb trigger can quickly adapt to changing running conditions and has performed far beyond its design in terms of signal efficiencies. The trigger system showcases a number of pioneering concepts, among them the use of multivariate classifiers to identify b-hadrons and the buffering of events to local disks and their processing at a later time, when the LHC is not producing collisions. The design of the trigger system, its performance during 2011/2012 and improvements for data taking in 2015 are discussed. The redesign of the trigger system for the upgrade of the LHCb experiment in 2018 is outlined. |