ALICE silicon tracker upgrades for LHC Run 4 and beyond

Abstract

During the Long Shutdown 3 of the LHC (2026-2028) the ALICE experiment foresees an upgrade of the inner barrel of its Inner Tracking System: the ITS3.This new vertex detector is based on Monolithic Active Pixel Sensors produced in a commercial 65 nm CMOS technology. Each half-layer is realized with a single stitched sensor of 26 cm long and less than 50µm thick, bent to form a half-cylinder, and held in place with carbon foam supports. The detector is air cooled allowing for an extremely low material budget of 0.09X/X˙0 per layer. With respect to the current ALICE vertex detector, ITS3 will improve the pointing resolution by 50% and the tracking efficiency by 30% for hadrons of low transverse momentum.Parallelly, ALICE is designing a next generation heavy-ion experiment for LHC Run 5 and 6 (beyond 2035).Its tracking system will be based on a vertex detector, integrated in a retractable structure inside the beam pipe to achieve the best possible pointing resolution, and a large-area outer tracker, surrounding the vertex detector and covering the pseudorapidity range −4<η<4. Both systems will be based on the same MAPS technology developed for ITS3 and will have to satisfy stringent requirements: the innermost vertex detector layer, placed at 5 mm from the interaction point, must withstand an integrated radiation load of 9×1015 1MeV n˙eq/cm2 NIEL and 2.88MGy TID; the outer tracker, extending from the beam pipe to a maximum radius of about 80 cm, covers almost 60m2 of area.This proceeding will cover both the ITS3 upgrade and the projects for ALICE3 silicon tracker, highlighting their requirements, sensor specifications, mechanics and integration. It will showcase the results achieved during the ITS3 R&D and outline the challenges expected for the implementation of the ALICE 3 tracking system.