Upgrade of the ALICE experiment for LHC Run 3 and beyond - Markus Fasel For the ALICE Collaboration

Upgrade of the ALICE experiment
 for LHC Run 3 and beyond
 Markus Fasel
 For the ALICE Collaboration

Preparing ALICE for Run 3 2
 New opportunities and challenges for ALICE in Run 3
Physics opportunities for ALICE in run3
• Thermalization of (heavy) partons in the QGP
• Charmonia at low-pT: Probe of deconfinement
• Low-mass dileptons: Chiral symmetry Need for an upgrade of several systems of
 restoration the ALICE experiment
• Thermal photons: Initial state of the QGP
 • Improve readout rate
• Jet substructure, jet-X correlation: partonic
 energy loss in the medium • Improvement of pT and pointing resolution
• Search for bound states involving strange • Significant reduction of the data volume
 mesons
 • Preserve particle identification capability

Data taking conditions
• Run 2: PbPb @ 1 kHz
• Run 3: PbPb @ 50 kHz

 CERN-LHCC-2012-012, CERN-LHCC-I-022, ALICE-UG-001
 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

ALICE in Run 3 3
 New: Muon Forward Tracker (MFT)
New: Inner Tracking System

 Upgrade: Frontend
 readout of various
New: Fast detectors
Interaction Trigger
(FIT)

Upgrade: TPC
readout based on
GEM stacks New: Online data processing (O2)
 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

New Inner Tracking System (ITS2) 4
 J. Phys. G 41 (2014) 087002

 Standalone tracking efficiency (%)
 100
 ALICE
 80
 Current ITS
 Upgraded ITS
 Improved low-pT tracking 60
 efficiency
 40
 (> 90% for pT> 200 MeV/c)
 20

 0
 10-1 1 10
 p (GeV/c)
 ALI-PUB-103028 T

 400

 Pointing Resolution (µm)
 z ALICE
 350
 Current ITS (data)
 300 Upgraded ITS
• ALPIDE chip: Based on MAPS (Monolithic Active Pixel Sensor)
 rϕ
 • Thickness: 50 µm 250

 • Granularity: 2000 pixels/cm2 Improved pointing 200
• 7 Layers (3 layers Inner Barrel, 4 Layers Outer Barrel) resolution at primary 150
 z
• ~24k chips -> ~ 12.5G pixels vertex by more than 100
 rϕ
• Distance from the collision point: 22 mm factor 2 50
• Radiation lengh: 0.35%X0 (Inner Barrel) 0
• Readout rate: 100 kHz PbPb, 400 kHz pp 10-1 1 10
 p (GeV/c)
 ALI-PUB-103021 T
 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Upgrade of the Time Projection Chamber 5
 CERN-LHCC-2013-020, ALICE-TDR-016
 Readout: GEM stacks
 • 4-GEM stack
 • Avalanche creation in GEM hole
 • Dominant part of ions absorbed on top side
 of GEM stack
 • Ion backflow: < 1%
 • No more need for gating grid
 • Similar performance (i.e. dE/dx) as for MWPC

 Performance similar to Run 2

Frontend Electronics: SAMPA
 • 130 nm CMOS
 • 32 channels / chip
 • 10 bit ADC
 • Digitization at 5 MHz
 • Allows for continuous readout TPC can be operated at 50 kHz PbPb
 in continuous mode
 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Muon Forward Telescope: Track extrapolation
of muon tracks to the collision vertex 6
 CERN-LHCC-2015-001. ALICE-TDR-018
 •

 Correct Matching Rate
 -3.6 < η < -2.45 1

 • 5 Layers 0.8
 • 2 disks / layer
 ALICE MFT Upgrade
 • ALPIDE chips (same as 0.6
 Pb-Pb@ s
 NN
 = 5.5 TeV, 0-5%

 ITS2) 0.4 -3.6 < η < -2.5

 • 920 chips 0.2
 MUON / MFT Tracks matching
 MUON Track / MFT Clusters matching

 • Propagation of muons to 0
 0 2 4 6 8 10
 p (GeV/c)
 primary vertex ALI-PUB-93242
 T

 • Selection of muons from 140

 σX [µm]
 x/X0 = 1.0%
 secondary vertices 120 x/X0 = 0.8%
 x/X0 = 0.6%
 100

 80

 Performance (muon tracks, pT > 2 GeV) 60

 40
 • 90% matching efficiency to tracks from Muon Spectrometer
 20
 • ~30 µm pointing resolution
 0
 0 2 4 6 8 10
 p [GeV/c]
 ALI-PUB-93246 T

 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

The Fast Interaction Trigger 7
 CERN-LHCC-2013-019. ALICE-TDR-015

 Detector design similar to Run 2 detectors
 • FIT-V0 (FV0): Scintillator
 -19.5 m from IP
 • FIT-T0 (FT0): Cerenkov
 -0.8 m from IP • FIT-Diffractive Detector (FDD): Scintillator

 4

 Absolute resolution on centrality (%)
 ALICE Simulation
 3.5 Pb-Pb, sNN = 2.76 TeV
 3 T0+ Upgrade
 FIT Upgrade
17 m from IP 3.5 m from IP FV0 2.5 V0

 2

 • Fast min. bias collision trigger with latency < 425 ns 1.5

 • Collision time for TOF with ~ 20 ps time resolution 1
 • Luminosity monitor 0.5
 • Centrality measurement
 0
 • Event plane determination 0 10 20 30 40 50 60 70 80 90
 ALI−SIMUL−96169 Centrality (%)

 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Online data processing with O2 8
 CERN-LHCC-2015-006, ALICE-TDR-019
New challenges for data processing in Run 3
 • Continuous readout → multiple collisions overlapping in the TPC drift time
 • 50 kHz PbPb → Storing all raw data not feasible → significant compression needed

 O2: The ALICE Online-Offline Computing System

 2-level online reconstruction
 • First Level Processor (FLP):
 Receiving and preparing data from the detector
 • Event Processing Nodes (EPN):
 Online reconstruction
 EPN: ~2000 GPU & CPU

 Compressed raw format to disk
 • i.e. only clusters and tracks for the TPC
 Online calibration and data quality monitoring
 Adaption of workflows to continuous data taking

 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Installation and commissioning 9

 Preparation of the TPC Miniframe MFT, FIT-C ITS First Run 3
 TPC for installation installation installation installation installation collisions at 900 GeV
 Global commissioning

 R&D, production Stable
 beams

 Feb. 2020 Aug-Oct. Nov 2020 Dec 2020 Mar.- Apr Summer 2021 Feb
 2020 2021 2022
 O2 and computing: Will be tested with simulation and analysis challenges starting from Q3 2021

 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Installation and commissioning 10
 MFT and FIT-C
 installation (Dec. 2020)

 TPC installation (Aug-Oct 2020)
 Miniframe installation
 O2
 (Nov. 2020)
 Commissinoning

 ITS outer barrel installation
 March 2021

 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Physics performace with ALICE at Run 3 11

Beauty via non-prompt D-mesons Precise measurement of the D-
 meson fragmentation in jets

 Access to possible ρ-broadening

 Beauty via non-prompt J/Ψ in RAA of Λc
 forward direction
 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Physics with ALICE Run 3 in pp collisions at
√s=14 TeV 12
 ALICE-PUBLIC-2020-005
 Dedicated physics program in pp collisions at √s = 14 TeV in 2022-2024
 • ∫Ldt = 200 pb-1
 • Interaction rate: 500 kHz
 • Selection of interesting events during reconstruction on the EPN
 Ω +Ω / (π++π-)

 ALICE Upgrade projection
 Multiplicity slicing with mid-rapidity estimator

 10-3
 +-

 PYTHIA8
 DIPSY
 EPOS LHC

 pp, s = 7 TeV Nat. Phys. 13 (2017) 535
 Projection for 14 TeV pp, 200 pb-1
 10-4 p-Pb, sNN = 5.02 TeV PLB 728 (2014) 25
 Preliminary Pb-Pb, sNN = 5.02 TeV

 10 102 103
 ⟨dN ch/dη⟩|η|< 0.5
 ALI−SIMUL−160917 ALI-SIMUL-364812

 Particle production in high- Collective effects in small systems at Precision measurement of the dead-
 multiplicity events high-multiplicity cone effect with B-tagged jets
 … and more
 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

New ITS in Run 4 (ITS3) 13
 CERN-LHCC-2019-018. LHCC-I-034
 Replacement of 3 Inner Barrel Layers
 • Fully cylindrical
 • Sensor thickness: 20 – 40 µm
 • Material Budget: 0.05% X0 / layer
 • -2.0 < η < 2.0
 • Distance to collision point: 16 mm

 • ~ Factor 2 improvement of the pointing resolution at the primary vertex
 • ~ Up to factor 2 inprovement in the tracking efficiency for pT < 100 MeV/c
 • Up to factor 4 increase of the significance of Λc in PbPb collisions

 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Constraining nuclear PDFs: The FoCal 14
 EPJC 77, 163

 Substantial uncertainty on
 the gluon nuclear PDFs at
 small-x and low Q2
 !"# , $
 !"# , $ = %
 ! , $

Main observables sensitive to the gluon PDF: Stronger sensitivity to
• Direct photons (quark-gluon compton scattering) small-x by direct photons
• Heavy flavour (gluon fusion)
Isolation cut enhancing quark-gluon compton scattering
 CERN-LHCC-2020-009, LHCC-I-036
 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Design of the ALICE FoCal 15
 CERN-LHCC-2020-009, LHCC-I-036

 Electromagnetic calorimeter:
 • Low Granularity: Si-pad (16 layers)
 • High Granularity: MAPS, based on
 ALPIDE (2 layers)
 Shower tracking

• 3.2 < η < 5.8

 Hadronic and electromagnetic
 calorimeter
 • FoCal-E: Si+W sampling
 calorimeter EPICAL (ALPIDE) Full (pad-layer only)
 • FoCal-H: conventional pixel prototype modules for tests at
 sampling hadronic calorimeter (proton CT project) PS/SPS and in 2018
 13 TeV LHC beam
 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Expected performance of the FoCal 16
 CERN-LHCC-2020-009, LHCC-I-036
 180 ALICE Simulation
 FOCAL Upgrade
 160
 140 PYTHIA pp s=13 TeV
 p > 5 GeV/c
 T,clust
 120
 R=0.4
 100 HCAL+ECAL
 ECAL
 80 MC
 60 ECAL MC

 40
 20
 0
 0 10 20 30 40 50 60
 p (GeV)
ALI-SIMUL-96150 T,iso
 ALI-SIMUL-313019

 Photon isolation: FoCal-E + FoCal-H Significant constraints on gluon nuclear pdf expected for direct
 photon measurements with FoCal

 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Outlook: New detector beyond Run 4 17
 arXiv:1902.01211

 |η| < 4 Particle
 Identification
 • Time-Of-Flight
 • Si timing sensors
Tracking
• CMOS-based
 silicon pixel
• Barrel and
 endcaps High-momentum
 particle
 identification
 B-field: 0.5 T • Shower Pixel
 Detector (SI-
 based) or RICH
 • Tracking and particle ID down to ~ tens of MeV • Barrel and
 • Excited charmonium states in heavy-ion collisions endcaps
 • Charmed baryons
 • Low-mass dielectron continuum (0 GeV/c2 < mee < 6 GeV/c2)
 • And more …
 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021

Summary 18
• Major upgrades for several detectors in Run 3:
 ITS2, TPC, MTF, FIT
• New data processing for the experiment designed to handle increased
 readout rate and data volume
• Significant improvement in precision, making new probes accessible in
 heavy-ion collisions in Run 3
• New detectors for Run 4
 • ITS3: Improved precision, for heavy-flavour and dielectron measurements
 • FoCal: Constrain nuclear PDFs at small-x
• New experiment, designed for multi-charm baryons, di-leptons and very
 low-pT, for Run 5+

 Markus Fasel | DIS 2021, Stony Brook University | April 12-16, 2021