The ITS3 detector and physics reach of the LS3 ALICE Upgrade

During Long Shutdown 3 of the Large Hadron Collider (2026-2028), the ALICE experiment is replacing its innermost three tracking layers with a new detector, the ITS3 (Inner Tracking System 3). It will be based on newly developed wafer-scale monolithic active pixel sensors, which are bent into truly cylindrical layers and held in place by light mechanics made from carbon foam. The unprecedentedly low material budget (0.07% per layer) and proximity of the first ITS3 layer to the interaction point (19 mm) will lead to a factor two improvement in pointing resolutions with respect to the present ITS2 at very low $\it{p}_{\mathrm{T}}$ (O(100) MeV/c). The pointing resolution of ITS3 for 1 GeV/c primary charged pions is 20 $\mu$m and 15 $\mu$m in the transverse and longitudinal directions, respectively. After the successful R&D phase (2019-2023), which demonstrated the feasibility of this innovative detector, the final sensor and mechanics are being developed right now. This contribution will shortly review the conceptual design and the main R&D achievements, as well as the current activities and road to completion and installation. It concludes with a projection of the improved physics performance, particularly for the heavy-flavour hadrons that will will be reached with the installation of this new detector.