The impact of applying WildCards to dead modules for FTK pattern banks on efficiency and data flow

Online selection is an essential step to collect the most interesting collisions among a very large number of events delivered by the ATLAS detector at the Large Hadron Collider (LHC). The Fast TracKer (FTK) is a hardware based track finder, for the ATLAS trigger system, that rapidly identifies important physics processes through their track-based signatures, in the Inner Detector pixel and SCT layers. FTK will do global track reconstruction after each Level-1 trigger for all tracks with pT > 1GeV to enable the Level-2 trigger to have early access to tracking information. Tracking is seeded by a pattern recognition step. Patterns are recognized with hits in seven out of eight possible detector layers. Because the detectors are not perfect, the presence of dead modules leads to a loss of efficiency in some regions. To recover efficiency, WildCards (WC) algorithm will be implemented in the FTK. The modules which WC algorithm is applied are assumed to always have hits. The WC algorithm recovers inefficiency but also causes higher data flow, that may exceed the hardware limitation. To correct this we will apply a penalty on patterns with WildCards, which will reduce slightly the efficiency but allows to reduce the data flow to values closer to the ideal ones.