Volume 476 - 42nd International Conference on High Energy Physics (ICHEP2024) - Operation, Performance and Upgrade (incl. HL-LHC) of Present Detectors
Operation and performance of the upgraded ALICE Inner Tracking System
J. Liu*  on behalf of the ALICE collaboration
*: corresponding author
Full text: pdf
Pre-published on: December 17, 2024
Published on: April 29, 2025
Abstract
The ALICE detector underwent significant upgrades during the LHC Long Shutdown 2 from 2019 to 2021. A key upgrade was the installation of the new Inner Tracking System (ITS2), comprising 7 layers with 12.5 billion pixels over 10 m$^{2}$, enhancing its tracking capabilities using the ALPIDE chips that are capable of recording Pb\textendash Pb collisions at an interaction rate of 50 kHz. It offers a significant improvement in impact parameter resolution and tracking efficiency at low transverse momentum, attributed to its increased granularity, low material budget of only 0.36% $\rm\ X_{0}$/layer for the innermost 3 layers and the closer positioning of the first layer to the interaction point.

ITS2 was successfully installed and commissioned in ALICE, becoming operational with the start of LHC Run 3. This paper provides an overview of its operation and initial performance results, focusing on calibration, tracking performance in both pp and Pb-Pb collisions, and studies on particle identification.
DOI: https://doi.org/10.22323/1.476.0920
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