ATLAS is one of the four major LHC experiments, designed to cover a wide range of physics topics. In order to cope with a rate of 40MHz and 25 interactions per bunch crossing, the ATLAS trigger system is divided in three different levels. The jet selection starts at first level with dedicated processors that search for high ET hadronic energy depositions. At the LVL2, the jet signatures are verified with the execution of a dedicated, fast jet reconstruction algorithm, followed by a calibration algorithm. Three possible granularities have been proposed and are being evaluated: cell based (standard), energy sums calculated at each Front-End Board and the use of the LVL1 Trigger Towers. In this presentation, the design and implementation of the jet trigger of ATLAS will be discussed in detail, emphasazing the major difficulties of each selection step. The performance of the jet algorithm, including timing, efficiencies and rates will also be shown, with detailed comparisons of the different unpacking modes.
ASJC Scopus subject areas
- Physics and Astronomy(all)