The ITS3 detector and physics reach of the LS3 ALICE Upgrade

¹ Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Institute of Modern Physics, Fudan University, 200433, Shanghai, China
² Key Laboratory of Quark & Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, 430079, Wuhan, China

^* e-mail: chunzheng.wang@cern.ch

Published online: 27 January 2025

Abstract

During Large Hadron Collider (LHC) Long Shutdown 3 (LS3) (2026-30), the ALICE experiment is replacing its inner-most three tracking layers by a new detector, 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. Unprecedented low values of material budget (per layer) and closeness to interaction point (19 mm) lead to a factor two improvement in pointing resolutions from very low p_T (O(100MeV/c)), achieving, for example, 20 µm and 15 µm in the transversal and longitudinal directions, respectively, for 1 GeV/c primary charged pions. After a successful R&D phase 2019-2023, which demonstrated the feasibility of this innovational detector, the final sensor and mechanics are being developed. This contribution briefly reviews 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, in particular for heavy-flavour hadrons, as well as for thermal dielectrons, that will come into reach with this new detector installed.