An Upgraded ATLAS Central Trigger for 2014 LHC Luminosities

During 2011, the LHC reached instantaneous luminosities of 4*10^33 cm-2*s-1 and produced events with up to 24 interactions per colliding proton bunch. Thisplaces stringent operational and physical requirements on the ATLAS Trigger in order to reduce the 40MHz collision rate to a manageable event storage rate of ~400Hz and, atthe 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 75kHz and adecision latency of less than 2.5us. It is primarily composed of the Calorimeter Trigger, Muon Trigger, and the Central Trigger Processor which are implemented in custom builtVME electronics. The Central Trigger Processor collects trigger information from all Level-1 systems and produces a Level-1 trigger decision that initiates the readout of all ATLAS subdetectors. In 2014, the LHC will run at a center of mass energy of 14 TeV, compared to the current 8 TeV, and the luminosity will exceed 10^34 cm^-2*s^-1. With higher luminosities, therequired number and complexity of Level-1 triggers will increase in order to satisfy the physics goals of ATLAS while keeping the total Level-1 rates at or below 100kHz. 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. We will discuss 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.