ALICE 3

A next-generation heavy-ion
detector for LHC Run 5
Nicola Nicassio (CERN, University and INFN Bari)
for the ALICE Collaboration
Quark Matter – April 6-12, 2025
Nicola Nicassio – Quark Matter 2025 1
ALICE roadmap

2022 - 2026 2030 - 2033

Run 5

LS3 & Run 4: ITS3 (talk by Magnus Mager), FoCal (talk by Tommaso Isidori)

ALICE 3 milestones
• Plan for dedicated heavy-ion programme for LHC Runs 5 and 6
- First ideas at Heavy-Ion town meeting (2018)
- Expression of Interest submitted as input to the European
Strategy for Particle Physics Update in 2019 arXiv:1902.01211
• Letter of Intent for ALICE 3: Review concluded with very positive
feedback by the LHCC in March 2022 arXiv:2211.02491

• Scoping Document: Review just completed CERN-LHCC-2025-002

Nicola Nicassio – Quark Matter 2025 2

ALICE 3 physics goals
Early stages: temperature, chiral symmetry restoration Understanding fluctuations of conserved charges
• Dilepton and photon production, elliptic flow • Hadron correlation and fluctuation measurements
Nature of exotic hadrons
Heavy flavour diffusion and thermalization in the QGP
ഥ correlations • 𝐷-𝐷 femtoscopy, production yields
• Precise beauty flow at low 𝑝T, 𝐷-𝐷
Beyond QGP physics
Hadronization in heavy-ion collisions • Ultra-soft photon production: test of Low’s theorem
• Multi-charm baryon production: charm thermalisation • Search for axion-like particles in ultra-peripheral Pb-Pb
• Excited quarkonium states: dissociation and regeneration • Search for super-nuclei (c-deuteron, c-triton)

Pb-Pb
𝝉 [fm/c] Hc,b
Hcc
Hccc

Nicola Nicassio – Quark Matter 2025 3

ALICE 3 detector concept
Key features
• Compact detector, ultra-light all-silicon
retractable vertex detector and tracker
• Superconducting solenoid, 𝐵 = 2 T
• Extensive particle identification
• Large acceptance: 𝜂 < 4
• Continuous readout + online processing

Nicola Nicassio – Quark Matter 2025 4

ALICE 3 vertex detector
Requirements 80 cm
IRIS Breadboard Model
• Pointing resolution ≈ 10 μm @ 𝑝𝑇 = 200 MeV/𝑐
• ∝ 𝑟0 ⋅ 𝑋/𝑋0 → 𝑟0 = 5 mm, 𝑋/X0 ≈ 0.1 % / layer
• Spatial resolution of 2.5 μm → 10 μm pixel pitch
• 100 ns time resolution
Implementation Rotary
• Wafer-sized, bent MAPS* (leveraging ITS3 R&D) petals
• Retractable detector: 3 (barrel) + 3⋅2(disk) layers
in secondary vacuum within the beam pipe
Challenges Stable beam
• Mechanics
• Integration Beam injection
in vacuum
• Radiation
tolerance
NIEL TID
MeV neq/cm 2 Mrad
5x better
1016 300 𝜂 <4
*MAPS = Monolithic Active Pixel Sensors Beam injection Stable beam
Nicola Nicassio – Quark Matter 2025 5
Middle and Outer Tracker layers
Requirements
• 𝜎𝑝T /𝑝T ≈ 1 % up to |𝜂| = 4
• ∝ 𝑋/𝑋0 → X/X0 ≈ 1 % / layer
• 𝜎𝑝𝑜𝑠 ∼ 10 μm → 50 μm pitch
• 100 ns time resolution
Implementation
• MAPS, ≈ 60 m2 active area
• 8(barrel)+9⋅2(disk) layers
• 𝑅𝑜𝑢𝑡 ≈ 80 cm, z < 3.5 m
Challenges
• Industrialization of the module
assembly, power consumption

Cyli ndrical shell

R ≈80 cm

support
brackets
dumm y modules
for cooling tests

Nicola Nicassio – Quark Matter 2025 6

Middle and Outer Tracker layers
Requirements
• 𝜎𝑝T /𝑝T ≈ 1 % up to |𝜂| = 4
• ∝ 𝑋/𝑋0 → X/X0 ≈ 1 % / layer
• 𝜎𝑝𝑜𝑠 ∼ 10 μm → 50 μm pitch
Poor Δ𝑝T/𝑝T
• 100 ns time resolution with B = 1 T
Implementation for 𝜂 = 3-4
• MAPS, ≈ 60 m2 active area
• 8(barrel)+9⋅2(disk) layers
• 𝑅𝑜𝑢𝑡 ≈ 80 cm, z < 3.5 m
Challenges
• Industrialization of the module
assembly, power consumption

Cyli ndrical shell

R ≈80 cm

support
brackets
dumm y modules
for cooling tests

Nicola Nicassio – Quark Matter 2025 7

Superconducting 2T solenoid
Superconducting cable: options under investigation
• Al-cladded Nb-Ti "standard cable": baseline technology
• Cu-cladded Nb-Ti cable: much heavier, requires specific design
• Al-cladded MgB2 cable: allows larger operation temperature, but
requires validation and specific design for a large magnet system

Furukawa

Nicola Nicassio – Quark Matter 2025 8

PID: The TOF detector
See also posters by Stefania
Bufalino and Bianca Sabiu

Requirements Advanced Readout CMOS Architectures with

Depleted Integrated sensor Arrays (INFN Project) ARCADIA CMOS-LGAD
• 𝑒/𝜋, 𝜋/𝐾 and 𝐾/𝑝 separation up to beam test results
≈ 0.5, 2 and 4 GeV/𝑐, respectively
→ ∝ 𝐿/𝜎𝑇𝑂𝐹 → 𝜎𝑇𝑂𝐹 ≈ 20 ps
Technology options
• 2 barrel + 1 forward layers, ≈45 m2
- Novel monolithic CMOS LGADs
- Single/double LGADs
Demonstration of timing with gain: good prospects to
- SiPMs (in combination with RICH) approach target with new sensor layout and thinning
Challenges
• Achievement of the target 20 ps
resolution at "full-system" level
SiPMs beam
LGAD beam test results
CERN-LHCC-2025-002 test results

Nicola Nicassio – Quark Matter 2025 9

PID: The RICH detector
Requirements Aerogel Projective bRICH layout Photodetector
• Extend PID beyond TOF limits
- 𝑒/𝜋, 𝜋/𝐾 and 𝐾/𝑝 separation up to
≈ 2, 10 and 16 GeV/𝑐, respectively
→ n = 1.03 (barrel), n = 1.015 (forward)
→ 𝜎𝑅𝐼𝐶𝐻 ≈ 1.5 mrad at saturation
Implementation
• bRICH: Aerogel + SiPMs (≈30 m2)
• fRICH: Aerogel + HRPPDs (≈8 m2)
Challenges 2024 beam test results using Radioroc + PicoTDC
• SiPM radiation tolerance and DCR
mitigation with cooling + annealing

CERN-LHCC-2025-002

Nicola Nicassio – Quark Matter 2025 10

PID: The MID detector
Requirements
• Muon ID down to 𝑝𝑇 ≈ 1.5 GeV/𝑐
• Pion rejection > 96 % for 𝜂 < 1.25
Hadron absorber
• Thickness of ≈ 70 cm at 𝜂 = 0
Muon chambers
• Δ𝜂 x Δ𝜙 granularity → 5 x 5 cm2 cells
• 2 layers of plastic scintillator + SiPMs
• Alternative options: MWPCs, RPCs

MWPC

JINST 19 (2024) 04, T04006 JINST 19 (2024) 04, T04006

Nicola Nicassio – Quark Matter 2025 11

Forward Conversion Tracker (FCT)
Requirements
• Photon ID for 𝑝𝑇 ≈ 1-10 MeV/𝑐
• Pseudorapidity coverage: 4 < 𝜂 < 5
• Minimization of material in front of
the FCT crucial for bkg suppression

Implementation
• Detection via photon conversion
- Tracker disks or extra converter Background sources
• Extra disks with pixel trackers
- MAPS, 𝑋/𝑋0 ≈ 1% per layer
• Dedicated dipole magnet
- Field component 𝐵𝑦 ≈ 0.3 T

Challenge
• Background suppression

Nicola Nicassio – Quark Matter 2025 12

Forward Detector (FD)
FD tasks
• Luminometer and interaction trigger
• LHC background monitoring
• Collision-time and Vertex position
• Forward multiplicity and centrality
• … and much more
A side C side
Implementation
• Two large segmented disks at forward
and backward rapidity, 4 < 𝜂 < 7
• Sensitive part made of fast plastic
scintillator from Eljen technology

See also poster by Podist Kurashvili

Nicola Nicassio – Quark Matter 2025 13

Dileptons and QGP temperature
Projection for thermal dielectron 𝑚𝑒𝑒
HF bkg

Dileptons are produced in all stages of a heavy-ion collision

No strong interactions ⇒ Messengers of collision evolution
Inference of QGP temperature 𝑻 using thermal
dielectron 𝒎𝒆𝒆 spectrum at 𝒎𝒆𝒆 > 1.1 GeV/𝒄𝟐
arXiv:2211.02491
Crucial requirements
• Very good electron identification down to low 𝑝𝑇
• Small material budget (𝛾 conversion background)
• Good pointing resolution (heavy flavour decays) v
High-precision dielectron based QGP temperature
measurements only possible with ALICE 3
Nicola Nicassio – Quark Matter 2025 14
Dileptons and time evolution
HF bkg
Projection for 𝑇 as a function of 𝑝𝑇 ,𝑒𝑒

Dileptons are produced in all stages of a heavy-ion collision

No strong interactions ⇒ Messengers of collision evolution
Probing time dependence of temperature using
double-differential spectra of 𝒎𝒆𝒆 and 𝒑𝑻,𝒆𝒆 arXiv:2211.02491
Crucial requirements
• Very good electron identification down to low 𝑝𝑇
• Small material budget (𝛾 conversion background)
• Good pointing resolution (heavy flavour decays) v
High-precision dielectron based QGP temperature
measurements only possible with ALICE 3
Nicola Nicassio – Quark Matter 2025 15
Heavy-quark correlations
ഥ 0 correlation
Projection for 𝐷0 𝐷

Near side pairs

Back-to-back pairs

arXiv:2211.02491
Angular decorrelation of heavy-flavour hadrons

ALICE Run 3 + 4 projection

Powerful probe of QGP scattering

• Sensitive to energy loss and thermalization degree

• Strongest signal at low 𝑝𝑇
• Requires high purity, efficiency and 𝜂 coverage

Heavy-ion measurement only possible with ALICE 3

Nicola Nicassio – Quark Matter 2025 16

Multi-charm baryon reconstruction
Multi-charm baryons: powerful probe of hadron formation Strangeness tracking in Ξ++ decay
++
Ξ𝑐𝑐 → Ξ𝑐+ + 𝜋 +
Ξ𝑐+ → Ξ − + 2 𝜋 +
First ALICE 3 tracking layer at 5 mm

Track strange baryon (Ξ−) before it decays

High selectivity thanks to pointing resolution
Heavy-ion measurement only possible with ALICE 3

++ in Pb-Pb ++ in Pb-Pb
Significance for Ξ𝑐𝑐
Mass peak for Ξ𝑐𝑐

arXiv:2211.02491

arXiv:2211.02491

See also talk by Andrea Sofia Triolo and

poster by Jesper Karlsson Gumprecht
Nicola Nicassio – Quark Matter 2025 17
Conclusions
Summary
• ALICE 3 is needed to unravel the microscopic dynamics of the quark-gluon plasma
beyond current limits by fully exploiting the potential of the LHC as a heavy-ion collider
• ALICE 3 also addresses fundamental open questions in QCD physics and beyond
• Innovative detector concept to meet the requirements of the rich physics program
• Pioneering R&D with broad impact on future HEP and nuclear physics experiments

Outlook
• 2025-2026: Selection of technologies, focus on R&D challenges
• 2026-2027: Large-scale prototypes, Technical Design Reports

New Collaborators are welcome !

Nicola Nicassio – Quark Matter 2025 18
Thank you for your attention
Nicola.Nicassio@ba.infn.it

Nicola Nicassio – Quark Matter 2025 19

Backup

Nicola Nicassio – Quark Matter 2025 20

ALICE 3 motivation

2022 - 2026 2030 - 2033

Run 5

LS3 & Run 4: ITS3 (talk by Magnus Mager), FoCal (talk by Tommaso Isidori)

Main experimental goal of the ALICE Collaboration

Study the microscopic dynamics of the strongly-interacting matter produced in heavy-ion collisions
Run 3+4 will allow systematic measurements of Fundamental questions will remain open
• Medium effects on single heavy-flavour hadrons • QGP properties driving constituents to equilibrium
BUT • Partonic EoS and its temperature dependence
• Time averaged thermal QGP radiation • Underlying dynamics of chiral symmetry restoration
• Collective effects from small to large systems • Hadronization mechanisms of the QGP
Substantial improvement needed in detector performance and statistics

Next-generation heavy-ion experiment

Nicola Nicassio – Quark Matter 2025 21
ALICE 3 detector concept
Heavy-flavour hadrons (𝒑𝑻 → 𝟎, 𝜼 < 𝟒) Photons (𝒑𝑻 ≈ 𝟎. 𝟏-50 𝐆𝐞𝐕/𝒄, −𝟐 < 𝜼 < 𝟒)
• Vertexing (decay chain) • Electromagnetic calorimetry
• Tracking (invariant mass resolution) Quarkonia and exotica (𝒑𝑻 → 𝟎, 𝜼 < 𝟏. 𝟕𝟓)
• Hadron ID (background suppression) • Muon and 𝛾 ID
Dielectrons (𝒑𝑻 ≈ 𝟎. 𝟎𝟓-𝟑 𝐆𝐞𝐕/𝒄) Soft photons (𝒑𝑻 ≈ 𝟏-𝟓𝟎 𝐌𝐞𝐕/𝒄, 𝟒 < 𝜼 < 𝟓)
• Vertexing (HF background suppression) • Dedicated Forward Conversion Tracker
• Tracking (invariant mass resolution) Nuclei (𝒑𝑻 → 𝟎, 𝜼 < 𝟒)
• Electron ID (background suppression) • Identification of 𝑍 > 1 particles

Nicola Nicassio – Quark Matter 2025 22

Integration and running scenario
Installation of ALICE 3
• Around nominal IP2, inside of L3 magnet (not used)

Running scenario
• 6 running years with 1 month / year with heavy ions
• 35 nb−1 for Pb-Pb
- x 2.5 compared to Run 3 + 4
• Lighter species for higher luminosity under study
• pp at 𝑠 = 14 TeV: 3 fb−1 / year
- x 100 compared to Run 3 + 4

Nicola Nicassio – Quark Matter 2025 23

PID: The ECal detector
Sampling sector
Requirements
• High-energy electron and photon ID
- Up to 100 𝐺𝑒𝑉 for 𝜂 < 1.5
- Up to 250 𝐺𝑒𝑉 for -4 < 𝜂 < -1.5
• Energy resolution
𝜎𝐸 𝑎 𝑏
= ⊕ ⊕𝑐
𝐸 𝐸 𝐸

Implementation PbWO4 sector

• 2(barrel)+1(disk) layers Simulation

- Sampling Pb + scintillator
(à la ALICE EMCal/Dcal)
PWO
- High-resolution segment based
on PbWO4 crystals, 𝜂 < 0.22
(à la ALICE PHOS)
- SiPM based readout

Nicola Nicassio – Quark Matter 2025 24

Dileptons and QGP temperature
Projection for thermal dielectron 𝑚𝑒𝑒

HF bkg

Dileptons are produced in all stages of a heavy-ion collision

No strong interactions ⇒ Messengers of collision evolution
Inference of QGP temperature 𝑻 using thermal
dielectron 𝒎𝒆𝒆 spectrum at 𝒎𝒆𝒆 > 1.1 GeV/𝒄𝟐
arXiv:2211.02491
Crucial requirements
• Very good electron identification down to low 𝑝𝑇
• Small material budget (𝛾 conversion background)
• Good pointing resolution (heavy flavour decays) v
High-precision dielectron based QGP temperature
measurements only possible with ALICE 3
Nicola Nicassio – Quark Matter 2025 25
Dileptons and time evolution
Projection for 𝑇 as a function of 𝑝𝑇 ,𝑒𝑒

HF bkg

Dileptons are produced in all stages of a heavy-ion collision

No strong interactions ⇒ Messengers of collision evolution
Probing time dependence of temperature using
double-differential spectra of 𝒎𝒆𝒆 and 𝒑𝑻,𝒆𝒆 arXiv:2211.02491
Crucial requirements
• Very good electron identification down to low 𝑝𝑇
• Small material budget (𝛾 conversion background)
• Good pointing resolution (heavy flavour decays) v
High-precision dielectron based QGP temperature
measurements only possible with ALICE 3
Nicola Nicassio – Quark Matter 2025 26
Chiral symmetry restoration
Projection for thermal dielectron 𝑚𝑒𝑒

Dileptons are produced in all stages of a heavy-ion collision

No strong interactions ⇒ Messengers of collision evolution

Probing chiral symmetry restoration (CSR) mechanisms

using thermal 𝒎𝒆𝒆 spectrum for 𝒎𝒆𝒆 < 1.2 GeV/𝒄𝟐
𝜏𝜌 = 1.3 fm < 𝜏𝑄𝐺𝑃 ⇒ 𝜌 meson sensitive to medium

Modification of 𝝆 spectral function related to CSR

High-precision measurements with ALICE 3 provide

unique access to CSR mechanisms like 𝝆 − 𝒂𝟏 mixing
Nicola Nicassio – Quark Matter 2025 27
Heavy-quark transport

Access to (heavy-)quark transport properties in the QGP at hadron level

• Precise 𝑅𝐴𝐴 and 𝜈2 measurements of charm and beauty hadrons down to low 𝑝𝑇 → diffusion coefficients 𝑫𝒔
• Expect beauty thermalisation slower than charm → smaller 𝑣2
Need for ALICE 3 performance (pointing resolution, acceptance) for precise measurements down to low pT
Nicola Nicassio – Quark Matter 2025 28
Hadron formation
Multi-charm baryons: powerful probe of hadron formation

• Require production of multiple charm quarks

• Contribution from single parton scattering very small

Very large enhancement predicted by Statistical Hadronisation

Model in Pb-Pb collisions → Test degrees of thermalization

ALICE 2(.1):
• Single charm states (c = 1)
ALICE 3:
• Multi-charm states (c > 1)

J. High Energ. Phys. 2021, 35 (2021)

With ALICE 3 measure additional states to test physical picture
Large 𝜼 acceptance → Probe charm density dependence Yield scaling with 𝑔𝑐𝑛 for 𝑛-charm states

Nicola Nicassio – Quark Matter 2025 29

Nature of exotic bound states
+ tetraquark state discovered in
𝑇𝑐𝑐
July 2021 by LHCb CERN-EP-2021-165

?
Search for possible DD bound states using two particle
momentum correlation:

𝐶 𝑘 ∗ = න 𝑑3𝑟 ∗ 𝑆 𝑟 ∗ Ψ k ∗, r ∗ 2

connected to source function/size and two-particle wave function

Behaviour of 𝐶 𝑘 ∗
→ Get information on interaction potential
→ Dissociation/regeneration of exotic states in QGP
Possible with ALICE 3 thanks to pointing resolution + acceptance
Nicola Nicassio – Quark Matter 2025 30
Fluctuation of conserved charges
ALICE 3 Projection for 6th cumulant
Baryon number susceptibility of QGP
• Calculable with lattice QCD
• Accessible via cumulants of net-proton number fluctuations

Higher-order cumulants
• Phase transition between QGP and HG
ഥ)/𝒌𝟐 (𝒑 − 𝒑
→ 𝟒𝝈 observation in reach with ALICE 3: 𝒌𝟔(𝒑 − 𝒑 ഥ)

Lower-order cumulants
• Long-range rapidity correlations
→ Large acceptance is crucial

Net-baryon fluctuation measurements

profit from large ALICE 3 acceptance and very good PID
→ Can be extended to net-charm fluctuations (D mesons)

Nicola Nicassio – Quark Matter 2025 31

Fluctuation of conserved charges
Baryon number susceptibility of QGP
• Calculable with lattice QCD
Pseudorapidity dependence of normalised
• Accessible via cumulants of net-proton number fluctuations second cumulants of net-protons

Higher-order cumulants
• Phase transition between QGP and HG
→ 4𝜎 observation in reach with ALICE 3: 𝑘6 (𝑝 − 𝑝)/𝑘
ҧ 2(𝑝 − 𝑝)ҧ

Lower-order cumulants
• Long-range rapidity correlations
→ Large acceptance is crucial

Net-baryon fluctuation measurements

profit from large ALICE 3 acceptance and very good PID
→ Can be extended to net-charm fluctuations (D mesons)

Nicola Nicassio – Quark Matter 2025 32

Ultra-soft 𝜸 production
Inclusive pp collisions at s = 13 TeV
Expected yields for signal and backgrounds

𝛾 production via inner bremsstrahlung

Observed yield not understood

• Cross section computable with Low-theorem
• Excess observed at lower 𝑠 in association with hadrons

Systematic study with ALICE 3

• 𝑝𝑝 → 𝑝𝑝𝜋 +𝜋 −𝛾
• 𝑝𝑝 → 𝑝𝑝 𝐽/𝜓 𝛾 → 𝑝𝑝𝑒 +𝑒 −𝛾
• Inclusive 𝑝𝑝 collisions vs charged particle multiplicity

Large acceptance → Clean selection of exclusive process

Nicola Nicassio – Quark Matter 2025 33

Nuclear-states: Charm-nuclei
Impact parameter distribution Invariant mass distribution

Unique sensitivity to undiscovered charm nuclei

For c-deuteron (Λ𝑐 𝑛) : reach significance of 50 for one month Pb-Pb fully integrated (centrality, 𝑝𝑇 𝜂)
For c-triton (Λ𝑐 𝑛𝑛) : reach significance of 2.5 for one month Pb-Pb fully integrated (centrality, 𝑝𝑇 𝜂)

Nicola Nicassio – Quark Matter 2025 34

Search for Axion-Like Particles
Axion-Like Particles (ALPs) ALP search: expected sensitivity as a
• Pseudoscalar particles appearing in BSM extensions as function of 𝑚𝑎 and ALP-𝛾 coupling 1/Λ𝑎
Goldstone bosons (Dark matter candidates/mediators)

Search for ALPs in ultra-peripheral collisions

• Strategy: Look for peaks in two-photon invariant mass spectrum

• Background: 𝜋 0𝜋 0 photo-production, light-by-light scattering

ALICE 3 uniqueness
• Large detector coverage 𝜂 < 4
• Capability to measure 𝛾 down to small 𝐸 (≥ 50-100 MeV)

Nicola Nicassio – Quark Matter 2025 35

ALICE 3 posters at QM

• Jesper Karlsson Gumprecht: Fast simulations with ALICE 3

• Stefania Bufalino: Latest results on monolithic sensors with additional gain

produced with a 110 nm technology for the ALICE 3 Time of Flight detector

• Bianca Sabiu: SiPMs in direct detection of MIPs for the future ALICE 3
detector at the LHC

• Podist Kurashvili: Forward Detectors for the ALICE 3 upgrade

Nicola Nicassio – Quark Matter 2025 36