An upgraded ATLAS central trigger for 2014 LHC luminosities

Current LHC instantaneous luminosity puts stringent operational and physical requirements on the ATLAS Trigger in order to reduce the 40 MHz collision rate to a manageable event storage rate of few hundreds of Hz and, at the same time, selecting those events considered interesting. The Level-1 Trigger is the first rate-reducing step in the ATLAS Trigger, with an output rate of 75 kHz and a decision latency of less than 2.5 μs. It is primarily composed of the Calorimeter Trigger, Muon Trigger, and the Central Trigger Processor which are implemented in custom built VME electronics. The Central Trigger Processor collects trigger information from all Level-l systems and produces a Level-l trigger decision that initiates the readout of all ATLAS subdetectors. In 2014 the LHC will run at center of mass energy of 14 TeV, compared to the current 8 TeV, and the luminosity will exceed 10 4 cm^-2 s^-1. With higher luminosities, the required number and complexity of Level-1 triggers will increase in order to satisfy the physics goals of ATLAS while keeping the total Level-l rates at or below 100 kHz. It is also foreseen to install a Level-1 Topological trigger in the 2013 shutdown period to further improve the selection at this trigger stage. In order to process more trigger inputs and the additional hardware, the Central Trigger Processor will be upgraded during the 2013 shutdown. In this presentation the current Central Trigger Processor, the justification for the upgrade, and the proposed upgrade to satisfy the requirements of the 2014 physics run at the LHC will be discussed.