Simulation and tracking performance of the LHCb Tracker with a redesigned silicon inner tracker

At the design luminosity of the LHCb upgrade, $\cal{L}_\rm{inst}$ = 2 x 10$^{33}$ cm$^{-2}$s$^{-1}$, the increased occupancy of the Outer Tracker causes a significant deterioration of its performance. On the other hand, the present Inner Tracker hardly shows any deterioration in tracking efficiency. It is therefore proposed to increase the size of the Inner Tracker. In addition, the resulting decrease of the Outer Tracker coverage close to the beam-line further reduces the Outer Tracker occupancy. In this note we describe the simulation and tracking efficiency studies of the Outer Tracker with a larger and lighter silicon inner tracker, the "SilT-light" detector. They show that a good tracking performance can be achieved at upgrade luminosities.