[Paper Review] Letter of intent for ALICE 3: A next-generation heavy-ion experiment at the LHC

ALICE Collaboration|arXiv (Cornell University)|Nov 4, 2022

Particle Detector Development and Performance44 citations

TL;DR

Proposes ALICE 3, a high-rate, ultra-low-mass silicon-based detector near the interaction point, to unlock heavy-flavour, electromagnetic, and small-system QGP physics at the LHC with improved vertexing, tracking, and PID.

ABSTRACT

This document describes the plans of the ALICE Collaboration for a major upgrade of its detector, referred to as ALICE 3, which is proposed for physics data-taking in the LHC Run 5 and beyond. ALICE 3 will enable an extensive programme to fully exploit the LHC for the study of the properties of strongly interacting matter with high-energy nuclear collisions. The proposed detector layout, based on advanced silicon sensors, features superb pointing resolution, excellent tracking and particle identification over a large acceptance and high readout-rate capabilities. This document discusses the proposed physics programme, the detector concept, and its physics performance for a suite of benchmark measurements.

Motivation & Objective

• Motivate a next-generation detector to address unresolved questions about the quark–gluon plasma (QGP) and heavy-flavour dynamics after Run 4 at the LHC.
• Design a detector with ultra-low material budget, very close vertexing, and high-rate capabilities to enable precision heavy-flavour, electromagnetic, and exotic-state measurements.
• Demonstrate the physics performance benefits of a novel CMOS-based, high-readout detector in Pb–Pb and smaller systems.
• Outline the required R&D, luminosity scenarios, and operation plans to optimize ALICE 3’s impact across heavy-ion and pp programs.

Proposed method

• Propose a detector concept with wafer-scale CMOS Active Pixel Sensors thinned to ~30 micrometers bent into cylinders for minimal material.
• Describe an outer tracker with barrel and endcap layers to achieve ~1-2% momentum resolution over large acceptance.
• Implement particle identification via time-of-flight and a ring-imaging Cherenkov detector with silicon timing sensors.
• Incorporate a forward conversion tracker to measure photons at very low pT through e+e− conversions and plan high-rate data acquisition.
• Plan R&D programs to advance silicon tracking, timing, and photon sensors beyond current capabilities.

Experimental results

Research questions

• RQ1 What level of precision in heavy-flavour (charm and beauty) hadron measurements is required to disentangle transport, hadronisation, and QGP properties?
• RQ2 How can ultra-low-mass, high-resolution vertexing and high-rate data taking enable measurements of multi-heavy-flavour hadrons, exotic states, and thermal dileptons at the LHC?
• RQ3 What are the optimal ion species and luminosities to maximize ALICE 3’s physics reach beyond Pb–Pb runs?
• RQ4 Can electromagnetic probes (dileptons, photons) be measured differential enough to track QGP evolution and chiral symmetry restoration?
• RQ5 What new hadronic and beyond-Standard-Model opportunities (e.g., axion-like particles) become accessible with ALICE 3’s capabilities?

Key findings

• ALICE 3 enables high-precision heavy-flavour measurements down to thermal scales through improved pointing resolution and readout rate.
• The detector concept supports near-interaction-point tracking to achieve large rapidity coverage and reduced material budget.
• CMOS-based sensors and automated module integration enable high-volume production and improved tracking efficiency at low pT.
• The design facilitates multi-differential electromagnetic measurements and forward photon conversion studies for chiral symmetry and early QGP evolution insights.
• Projection studies indicate significant enhancements in heavy-flavour baryon measurements, multi-charm states, quarkonia, and di-electron/di-photon channels over current capabilities.
• Luminosity optimization with lighter ion species could substantially boost the nucleon-nucleon luminosity and expand ALICE 3’s physics program.