Track Reconstruction Efficiency in the ATLAS Inner detector

The tracking efficiency in the ATLAS inner detector is determined as a function of transverse momentum and pseudo-rapidity of the particle. Since the efficiency is estimated from simulation, the agreement between data and simulation is studied in detail and systematic effects are extracted. Especially, the effect of the detector materials is carefully re-examined. Since the end of 2011, the rapidly increasing number of interactions per bunch crossing introduces new challenges on tracking. This effect is also studied in detail.