CMS Level 1 Calorimeter Trigger Performance on Technical Proposal Physics
We examine the eeciency and rates of the CMS Calorimeter Level 1 Trigger as presented in the CMS Technical Proposal for selecting the events needed for use in the CMS physics program described in the Proposal. Speciic signals investigated include top decays to electrons, Standard Model Higgs decays to electrons and photons, signals from SUSY Higgs, and Gluino production. A variety of masses and SUSY parameters are investigated. The eeciencies are studied at the luminosity 10 33 cm ?2 s ?1 or 10 34 cm ?2 s ?1 depending on the expected rate of events as assumed in the CMS Technical proposal. A single set of Level 1 Calorimeter energy thresholds for electrons, jets and missing energy is selected to provide a 15 kHz rate at each of the two luminosity settings considered. It is shown that this set of cuts provides suuciently high eeciency and satisses CMS physics goals as stated in the Technical Proposal. We also explore the rate of B Physics signals that pass this high p t trigger.
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-detector 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.
The level-1 calorimeter trigger for the CMS detector at LHC
The authors present results from simulation studies and implementation ideas for the level-1 calorimeter trigger for the CMS detector at the LHC collider. QCD background trigger rates and signal efficiencies for electron and photon triggers using several simple level-1 algorithms are discussed. Jet trigger rates and efficiencies are studied for various calorimeter tower sums. Some of the technical challenges in implementing these simple trigger algorithms in a high rate environment are also explored. Design of a high speed adder ASIC is briefly discussed.