ALICE ITS Upgrade Collaboration

ALICE ITS Upgrade Collaboration
Name	ALICE ITS Upgrade Collaboration
Type	international scientific collaboration
Field	Particle physics; Nuclear physics; Detector technology
Headquarters	CERN, Geneva
Established	2014
Members	Multinational institutes and laboratories
Website	CERN ALICE

ALICE ITS Upgrade Collaboration

The ALICE ITS Upgrade Collaboration coordinated the design, construction, and deployment of the upgraded Inner Tracking System (ITS) for the ALICE (A Large Ion Collider Experiment) detector at the CERN Large Hadron Collider. It brought together university groups, national laboratories, and research institutes to deliver a high-resolution, low-mass pixel tracker aimed at improving measurements of heavy-flavour hadrons, quark–gluon plasma signatures, and rare probes in heavy-ion collisions, proton–proton collisions, and proton–lead collisions.

Background and Rationale

The initiative emerged from studies conducted after Run 1 and Run 2 of the Large Hadron Collider by teams including groups from ALICE (A Large Ion Collider Experiment), CERN, Brookhaven National Laboratory, GSI Helmholtzzentrum für Schwerionenforschung, and universities such as University of Birmingham, Università degli Studi di Padova, University of Heidelberg, Université de Strasbourg, and Tata Institute of Fundamental Research. Motivations cited proposals in reports from the European Strategy for Particle Physics and reviews by committees tied to IHEP, INFN, CNRS, STFC, and DOE/HEP that recommended replacing the original ITS to achieve better impact-parameter resolution, higher readout rate, and reduced material budget to extend sensitivity to low-transverse-momentum probes and charm and beauty hadrons observed in lead–lead collisions.

Collaboration Structure and Membership

The collaboration comprised working groups and institutes drawn from national laboratories and universities across Europe, Asia, and the Americas. Key institutional partners included CERN, INFN, CNRS-IN2P3, GSI Helmholtzzentrum für Schwerionenforschung, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, Tata Institute of Fundamental Research, Korea Institute of Science and Technology Information, and many university groups such as University of Glasgow, Université Paris-Saclay, University of Utrecht, University of Warsaw, National Technical University of Athens, University of São Paulo, University of Tokyo, and Sejong University. Governance followed models used by collaborations like ATLAS, CMS, LHCb, and ALICE (A Large Ion Collider Experiment), with coordinating boards, technical boards, physics working groups, and institutional representatives from agencies such as European Research Council-funded teams and national funding bodies like Science and Technology Facilities Council and Deutsche Forschungsgemeinschaft.

Detector Design and Technological Innovations

The upgrade replaced multiple layers of the previous silicon tracker with seven concentric layers of monolithic active pixel sensors (MAPS), leveraging developments from microelectronics industries and projects such as ALICE (A Large Ion Collider Experiment), STAR, and Belle II. Design choices integrated CMOS sensors developed in collaboration with foundries used by STMicroelectronics and research programmes linked to CNM, IMEC, and CEA-LETI. Innovations included ultra-thin silicon ladders, low-mass support structures inspired by work at CERN, DESY, and EPFL, CO2-based cooling systems analogous to implementations at LHCb and ATLAS, and high-speed data links building on developments from GBT (GigaBit Transceiver) projects and serializers used in CMS upgrades. The detector incorporated precise alignment strategies and calibration procedures akin to those employed by H1, ZEUS, and ALEPH.

Construction, Installation, and Commissioning

Fabrication occurred at distributed sites: sensor production and qualification at microelectronics facilities associated with CNRS, INFN, and CEA, ladder assembly at institutes such as University of Birmingham and GSI Helmholtzzentrum für Schwerionenforschung, and integration at CERN’s experimental halls. The installation sequence coordinated with the Long Shutdown 2 schedule at the Large Hadron Collider and involved precision machining, metrology campaigns referencing techniques from SNOLAB and DESY, and in-situ commissioning akin to procedures used for ATLAS and CMS pixel detectors. Global commissioning used cosmic-ray runs and beam tests at facilities like CERN PS, CERN SPS, DESY test beam, and PSI to validate tracking, timing, and readout chains before data-taking in Run 3.

Physics Goals and Performance Improvements

The upgraded ITS aimed to deliver order-of-magnitude improvements in impact-parameter resolution and tracking efficiency at low transverse momentum, enabling precision measurements of open heavy-flavour yields, heavy-quark energy loss, and collective flow coefficients for charm and beauty, complementing observables from ALICE (A Large Ion Collider Experiment), PHENIX, STAR, and NA61/SHINE. Enhanced readout rates targeted recording of minimum-bias lead–lead collisions and high-statistics samples comparable to programmes at RHIC and future facilities like FAIR and NICA. Improved vertexing and secondary vertex reconstruction supported studies of hadronization, charm-baryon production observed by LHCb and CMS, and rare probes such as low-mass dileptons and thermal radiation studied by NA60 and CERES.

Project Management, Funding, and Timeline

Management adopted staged milestones, risk matrices, and review processes used by large experiments such as ATLAS, CMS, LHCb, and ALICE (A Large Ion Collider Experiment). Funding combined contributions from national agencies including INFN, CNRS, STFC, DOE, NSF, MEXT, and collaborative grants like European Commission research instruments and ERC awards. Key project phases followed sensor R&D, pre-production, mass production, assembly, installation during Long Shutdown 2, and commissioning for Run 3, aligning with deliverables and technical reviews overseen by bodies similar to CERN Scientific Policy Committee and national review panels.

Category:Particle physics collaborations