The ALICE ITS upgrade

The Inner Tracking System (ITS) is the ALICE key detector for the study of heavy flavour production at LHC. This is attained by the identification of short-lived hadrons containing heavy quarks which have a mean proper decay length in the order of 100-300 μm. To accomplish this task the ITS is composed of six cylindrical layers of silicon detectors (two pixel, two drift and two strip) with a radial coverage from 3.9 to 43 cm and a material budget of 1.1% X0 per layer. In particular, the properties of the two innermost layers define the ITS performance in measuring the displaced vertex of such short-lived particles. Strategic choices for the ALICE upgrade in general will be made in 2012. In this context, one of the elements that are being studied is the upgrade of the ITS as based on the installation of a smaller beam pipe, recent improvements of detector technologies and the extension of its rapidity coverage. The installation of a smaller beam-pipe will allow reducing the distance between the first detector layer and the interaction vertex. The usage of the most recent monolithic or hybrid pixel detector technologies allow improving the detector material budget and intrinsic spatial resolution both by a factor 2 to 3 with respect to the present ITS. Under these assumptions, simulations indicate that an overall improvement of the impact parameter resolution as well as the transverse momentum resolution by a factor of at least 3 is possible. The ITS upgrade collaboration is now in the process of finalizing the Conceptual Design Report (CDR) covering the design and performance requirements, the upgrade options as well as the necessary R&D efforts.