The Level-1 Trigger of the CMS experiment at the LHC and the Super-LHC

The Compact Muon Solenoid experiment at the Large Hadron Collider at CERN observes proton-proton collisions at a centre of mass energy of 14 TeV and a frequency of 40 MHz. This results in a raw data rate exceeding 40 PByte per second, which must be reduced to a rate of 100 MByte per second before storage. This is achieved in two stages, a hardware trigger (Level-1 Trigger) and a software trigger (Higher Level Trigger). The Global Calorimeter Trigger is a central component in the level-1 trigger, selecting interesting ‘physical’ events from the background of events by identifying calorimetric energy patterns and features. The development of the Global Calorimeter Trigger required the use of several modern telecommunication technologies and is discussed here, with particular emphasis on the design and testing of the Source Card. Although the Large Hadron Collider has yet to start operation, design of an upgraded accelerator (called the Super Large Hadron Collider) is already under way. This upgrade will improve on the design luminosity of the LHC by a factor of 10, increasing the number of collisions per bunch crossing by the same factor. Such an increase would require changes to both the algorithms and the architecture of the level-1 trigger, in particular requiring the inclusion of tracking information. Several possible tracker and trigger architectures for high luminosity running are shown here. By introducing an on-detect or pT-cut, one of the schemes offers a reduction in the tracker data rate by approximately two orders of magnitude, this being sufficient to allow the inclusion of tracking data in the level-1 trigger. A case study into the identification of electrons in high pile-up environments using this kind of tracking information is also presented; it is shown that the use of tracking information may be used to recover the current level-1 trigger rate.