CMS high-level triggering

The LHC at CERN will provide proton–proton collisions at a centre-of-mass energy of 14 TeV and a bunch crossing interval of 25 ns. At design luminosity, L=1034 cm−2 s−1, this will result in an inelastic pp interaction rate of 1 GHz. The CMS experiment will have a multi-level trigger system in order to reduce this rate to about 100 Hz for events written to mass storage. The architecture of the CMS Trigger and Data Acquisition system with emphasis on the High Level Trigger system is described.