Wednesday 18 May 2011 Speaker: Nikos Konstantinidis (University College, London) Title: "A hardware track trigger for ATLAS at HL-LHC". Abstract: The HL-LHC, the planned high luminosity upgrade for the LHC, will increase the collision rate in the ATLAS detector approximately a factor of 5 beyond the design, while increasing the number of pile-up collisions in each event by a similar factor. This means that the level-1 trigger must achieve a higher rejection factor in a more difficult environment. I will review the options that ATLAS is exploring for upgrading its level-1 trigger system, and focus on the use of tracking information at level-1. In particular, ATLAS is considering a possible design which splits the level-1 trigger into a two-level system in which the first level uses only calorimetry and muon chambers to reduce the original rate and defines regions of interest in which to extract information from the tracking systems. A two-buffer design on all front-end electronics allows for a potentially significantly longer decision time for the second level while keeping the data bandwidth and buffer sizes moderate.