Upgrade of the ATLAS Level-1 Trigger with event topology information

The Large Hadron Collider (LHC) in 2015 will collide proton beams with increased luminosity from \unit{10^{34}} up to \unit{3 \times 10^{34}cm^{-2}s^{-1}}. ATLAS is an LHC experiment designed to measure decay properties of high energetic particles produced in the protons collisions. The higher luminosity places stringent operational and physical requirements on the ATLAS Trigger in order to reduce the 40MHz collision rate to a manageable event storage rate of 1kHz while at the same time, selecting those events with valuable physics meaning. The Level-1 Trigger is the first rate-reducing step in the ATLAS Trigger, with an output rate of 100kHz and decision latency of less than 2.5$\mu s$. It…