ALICE upgrade overview - Indico · 2018. 11. 21. · ITS IB Staves Module assembly machine sensors thinned to 50mm 9 chips, stave length ~450 mm for IB HIC for IB Positioning Stave

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ALICE upgrade overview

Zhongbao Yin

(For the ALICE Collaboration)

Central China Normal University

The fifth Annual Conference on Large Hadron Collider PhysicsMay 15-20, 2017, Shanghai, China

Zhongbao Yin@LHCP201720/5/2017

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Outline

• Introduction

• ALICE physics goals and upgrade strategy

• Overview of detector upgrades (LS2 2019-2020)

• Expected performance on selected topics

12Zhongbao Yin@LHCP201720/5/2017

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ALICE dedicated to heavy-ion physics at the LHC

An expanding and cooling fireball Relativistic Heavy Ion Collisions produce a complex system of strongly interacting QCD matter—— Quark Gluon Plasma

ALICE main goals to study the properties of the QGP:• Thermodynamics• Flow • Evolution• Parton interaction with the medium

Using several probes in a broad pT range:• heavy-flavor, quarkonia, jets, photons, dileptons, strangeness,…


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EMCAL

TRD, TOF

TPC

HMPID

PHOS, DCAL

ITS

Present detector layout

Central barrel-0.9<h<0.9

Muon arm-4<h<-2.5

• Designed to cope with very high charged particle multiplicities• Excellent tracking and particle identification of charged particles over wide pT range


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Excellent tracking and vertexing

T

T

pT

T

pp

p/1

Int. J. Mod. Phys. A 29, 1430044 (2014)


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Excellent particle identification capabilityInt. J. Mod. Phys. A 29, 1430044 (2014)


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Physics reach & limitations

• Measurements on a wide range of observables, from bulk particle production to specific probes, to characterize the deconfined hot and dense medium created in heavy-ion collisions at the LHC. [See talk by Andrea Dainese]

• But some probes not fully exploited due to insufficient statistics or large combinatorial background.

• Heavy flavor, quarkonium, jets, direct photons, dileptons,…


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LHC Heavy Ion program

• A major ALICE detector upgrade for the LS2 to fully exploit the higher rate and

to improve the physics performance

• The LHC heavy-ion program will extend to Run 3 and Run 4

• 4 LHC experiments will take part in this program

• High interaction rate: 50 kHz

• Requested (ALICE) integrated luminosity: 10 nb-1 at B=0.5 T (+ 3 nb-1 at

B=0.2T)

• x10 with respect to Run 2, but actually x100 in minimum bias Pb-Pb collisions


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Physics goals for ALICE upgrade• Charm/beauty meson and baryon production in a wide momentum range,

down to very low pT

• Probe the quark-medium interaction (in-medium energy loss) and the QGP

transport coefficients

• Study degree of charm thermalization and possible hadronization via

coalescence

• J/y, y’ states and prompt/non-prompt J/y separation down to lowest pT in

wide rapidity range

• Charmonium dissociation and regeneration pattern as a probe of color de-

confinement and medium temperature

• Measurement of low-mass and low-pT di-leptons (vector mesons, thermal

virtual photon)

• Initial temperature, space-time evolution and equation of state of the QGP

• Chiral-symmetry restoration ➞ modification of r spectral function

• Jet quenching and fragmentation: PID of jet particle content, heavy

flavour tagging

• Light nuclei and hyper-nuclei

• Study their production mechanisms and degree of collectivity

ALICE Upgrade LoI，CERN-LHCC-2012-012，March 2013


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Physics goals for ALICE upgrade• Charm/beauty meson and baryon production in a wide momentum range,

down to very low pT

• Probe the quark-medium interaction (in-medium energy loss) and the QGP

transport coefficients

• Study degree of charm thermalization and possible hadronization via

coalescence

• J/y, y’ states and prompt/non-prompt J/y separation down to lowest pT in

wide rapidity range

• Charmonium dissociation and regeneration pattern as a probe of color de-

confinement and medium temperature

• Measurement of low-mass and low-pT di-leptons (vector mesons, thermal

virtual photon)

• Initial temperature, space-time evolution and equation of state of the QGP

• Chiral-symmetry restoration ➞ modification of r spectral function

• Jet quenching and fragmentation: PID of jet particle content, heavy

flavour tagging

• Light nuclei and hyper-nuclei

• Study their production mechanisms and degree of collectivity

For most of these observables S/B is very low, so it is not possible to implement dedicated triggers.


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Upgrade requirements and strategy

• Excellent vertexing resolution and tracking efficiency at low pT

• Increase tracking detector granularity and reduce material budget with new Inner Tracking System (ITS) at mid-rapidity and new Muon Forward Tracker (MFT) in front of the muon absorber at forward rapidity

• Large statistics (no dedicated trigger) with high interaction rate

• Increase readout rate with new GEM-based readout chambers for TPC and new readout electronics for several detectors

• Reduce data size and write all Pb-Pb interactions with minimum bias trigger at 50 kHz with new integrated Online and Offline (O2) system to perform first calibration and data reduction online

• Preserve PID capabilities at high rate

• Speed-up readout of PID detectors


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ALICE detector upgradeNew Inner Tracking System (ITS)

Muon Forward Tracker (MFT)

Both based on MonolithicActive Pixel Sensors(MAPS)

New Forward InteractionTrigger (FIT) to replace the V0 and T0 detectors

TPC with GEM based readout

+ improved readout for TOF, ZDC, TRD, MUON ARM+ new Central Trigger Processor+ new DAQ/Offline architecture


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New ITS design objectives

• Improve impact parameter resolution by a factor ~3 (5) in rj (z) @ pT = 500

MeV/c➜ Reduce pixel size: 50 mm x 425 mm 25 mm x 25 mm

➜ Go closer to interaction point:

• new smaller beam pipe: 2.9 cm 1.9 cm

• first layer with smaller radius (2.3 cm, currently 3.9 cm)

➜ Reduce material thickness: 50 mm silicon, ~0.3(0.8)%X0 per layer (currently

~1.13%X0)

• Improve tracking efficiency and momentum resolution at low pT

➜ Increase granularity

➜ Add 1 layer (from 6 to 7)

➜ Silicon pixel, drift, strip to all-pixels

• Exploit LHC luminosity increase Faster (x50) readout:

• readout Pb-Pb interactions up to 100 kHz

• Withstand radiation load (10 years operation): • TID: ~ 270 krad, NIEL: ~1.7x1012 1MeV neq/ cm2

• Reliability fast insertion/removal for yearly maintenance

• Possibility to access faulty components during yearly shutdown

• Services (power, cooling, R/O) connected only on one side

ITS upgrade TDR, J. Phys. G41 (2014) 087002 ，CERN-LHCC-2013-024


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New ITS layout

• 7-layer barrel fully equipped with dedicated Monolithic Active Pixel Sensors (MAPS): ALice PIxel DEtector (ALPIDE)

• Radial coverage: 23 – 400 mm • h coverage: |h| ≤ 1.3 • Total active area about 10 m2

• 24,000 pixel chips (12.5G pixels)• Spatial resolution: 5 mm

Material /layer : 0.3% X0 (IB), 0.8% X0 (OB)

Space Frame

Cold Plate

Cooling Ducts

Mechanical

Connector

9 Pixel Chips

Soldering Balls

Flex Printed Circuit

See Marielle Chartier’s talk in the Upgrade session II


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New ITS performance

Impact parameter resolution Tracking efficiency (ITS standalone)

40 μm at pT= 500 MeV/c ~60% at pT= 100 MeV/c


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ALPIDE – final versionProduction started Dec 2016, to be completed by Dec 2017

Key features:• Dimensions: 30 mm x 15 mm• Pixel Matrix: 1024 cols x 512 rows• Pixel pitch: 29 mm x 27 mm• Ultra-low power (entire chip): ~40 mW/cm2 (requirement < 100 mW/cm2)• Triggered acquisition (200 kHz Pb-Pb, 1 MHz pp) or continuous (progr. integration time:

1ms - ∞)

Inner Barrel: 50 mm thickOuter Barrel: 100 mm thick

High speed serial data output (HSO)•OB: 400 Mbit/s•IB: 600 Mbit/s or 1.2 Gbit/s


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ALPIDE performance

• Detection efficiency stays at 100% over wide range of threshold value

• Fake-hit rate is below 10-11

/pixel/event (requirement 10-6)

• Average cluster sizes vary between 1 and 3 pixels (for MIPs)

• Resolution of ~5μm at a threshold of 200 electrons

• Irradiated chips (NIEL/TID) show no degradation in resolution/efficiency


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From chips to staves

ITS IB Staves

Module assembly machine

sensors thinned to 50mm

9 chips, stave length ~450 mm for IB

HIC for IB

Positioning

Stave precise positioning end pieces

Cooling

Light-high thermal conductive Cold Plate

Stiffness

Light-stiff mechanical Space Frame


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Muon Forward Tracker

Extrapolating the muon track candidates to the interaction region is affected by the presence of the absorber.

➔Negative effect on the reconstruction of the kinematics and on the possibility to separate prompt and displaced muons.

Complementing muon spectrometer at forward rapidity


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• Muon tracks are extrapolated and matched to the MFT clusters before the absorber

• High pointing accuracy to separate charm and beauty signals

Complementing muon spectrometer at forward rapidity


• 5 circular pixel silicon double-plane disks

• 28x28 mm2 pixels, 0.7% X0 per disks

• 912 ALPIDE chips• Pseudorapidity coverage:

-3.6<h<-2.5

Better than 100 mm for pT > 1 GeV/c

See Marielle Chartier’s talk in the Upgrade session II

MFT TDR, CERN-LHCC-2015-001


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TPC upgrade

Standard GEM Pitch=140 μmHole =70 μm

TPC upgrade involves:• Replacing all readout wire chambers with

quadruple-GEM chambers. • The GEMs are designed to minimize ion

back flow to allow continuous, ungated and untriggered readout.

• Replacing the front end electronics with electronics based on a new ASIC (SAMPA) designed to allow continuous readout.

• Developing software to achieve compression of the 3.2 TB/s raw data from the TPC.

• Goal: Operate TPC at 50 kHz preserving current tracking, momentum resolution and PID performance

• Current TPC readout based on MWPC limits the event readout rate to 3.5 kHz

electrons

ions


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R&D on GEM technology

dE/dx resolution (with 55Fe) vs ion back flow

Several year R&D program developed a solution with 4-GEM chambers - Different GEM hole patterns on each GEM help to block ion backflow - Tradeoff between energy resolution (large gain in first foil) and ion back flow (IBF)

(small gain in first foil)

Standard pitch not rotated

Large pitch rotated

Large pitch not rotated

Standard pitch rotated

DV = 270 V

DV = 230 V

DV = 288 V

DV = 359 V

DV = 800 V

DV = 800 V

DV = 20 V

DV = 800 V

90-10-5 Ne-CO2-N2


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Upgrade TPC performance

• Momentum resolution preserved for ITS+TPC tracks

• PID efficiency via dE/dx measurement preserved

TPC TDR: CERN-LHCC-2012-012

Test beam @PS


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Readout & Online-Offline System (O2)

• Data (1.1 TB/s) transferred in

continuous mode or by using

minimum bias trigger to First-

Level Processors (FLPs)

• The heart beat triggers to ‘chop’

data in Sub-Time Frames (STFs)

to be inspected for initial data

volume reduction in FLPs.

• STFs assembled to Time Frames

(TFs) in the Event Process Nodes

(EPNs).

• On-the-fly data volume reduction

by EPNs synchronously.• Global reconstruction,

calibration and data

compression

• Further reconstruction performed

asynchronously to improve the

data quality.

• 85 GB/s to storage for Pb-Pb at

50 kHz interaction rate

• To keep up with the 50 kHz interaction rate,

the upgraded detectors (ITS and TPC) will be

read out continuously.

O2 TDR, CERN-LHCC-2015-00620/5/2017

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PHYSICS PERFORMANCE (FOR SELECTED OBSERVABLES)

See Cristina Terrevoli’s talk in the Upgrade session


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B±

Displaced J/y➞e+e-

at midrapitity down to 0 GeV/c

Primary J/y

e+

e-J/y

Primary vertex

Secondary J/y

e+

e-J/y

B

Lxy

• B± accessible with new ITS• A unique measurement at pT down to 0

at mid-rapidity at the LHC• Measure energy loss for b, quantitative

verification of DEc>DEb vs. pT

ALICE, CERN-LHCC-2013-024


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Access beauty at pT0 GeV/c

• New channel opened (B) + much larger precision on RAA (both via displaced J/y and non prompt D0)

• The study of non prompt J/y in m+m- channel is the key tool to measure B down to zero pT

With Muon Forward TrackerMFT TDR, CERN-LHCC-2015-001


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Lc+ and Lb

• Lc+ accessible down to 2 GeV/c

• Enhancement of heavy flavor baryon/meson ratio at intermediate pT in Pb-Pb collisions?

Information on thermalization and hadronization of charm quarks in the medium


• Lb accessible down to 4 GeV/c


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Di-lepton production

B = 0.2 TLint=3 nb-1

• Precision of the measurement will be improved significantly• Allows for an estimation of the temperature at various phases of system

expansion with 10-20% precision (stat.+syst.)• A unique measurement at the LHC

Simulation

Present ITS with Run2 expected statistics

Simulation

After ITS upgrade

The signal to be measured (after background subtraction) is thermal radiation from the QGP (shown in orange) and modification of the vector meson spectral function (shown in red)



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Summary

• A comprehensive ALICE upgrade on

detector/readout/computing in LS2 (2019-2020)

• Improve vertexing and tracking performance

• Enable Pb-Pb collisions readout rate at 50 kHz

• Unique physics program for precision QGP studies,

complementary with respect to the other LHC experiments• Focused on heavy flavor, quarkonia and low-mass di-leptons

• + much more (light-nuclei, jets, …)

• A Forward Calorimeter (to be installed during LS3) with focus

on saturation physics also under discussion within the

Collaboration


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References

CERN-LHCC-2013-024

CE

RN

-LH

CC

-2015-0

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CERN-LHCC-2013-019

CE

RN

-LH

CC

-2015-0

06

CE

RN

-LH

CC

-2012-0

12

CE

RN

-LH

CC

-2013-0

20


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New Fast Interaction Trigger Detector

• Requirements:– Preserve resolution– Increase acceptance– Integrate detectors

• To replace V0 and T0 detectors

• Good Time resolution < 30 ps Time zero

for PID

• Large acceptance

Trigger efficiency, centrality, beam gas

background reduction, for pp and Pb-Pb,

veto forward hadronic activity for the

detection of ultra-peripheral Pb-Pb collision

• Finer segmentation

Reaction plane determination


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FIT = T0+ and V0+

T0+ modules

− Improved T0− Rectangular quartz radiators− New sensors MCP-PMT− Larger acceptance− More channels− Upgraded electronics and readout

− Improved V0− Faster plastic scintillator− Monolithic structure− Reduced fiber length− New sensor (SiPM or MCP-PMT)− New electronics and readout

V0+ sectors


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FIT performance

Event plane resolution Centrality resolution


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FoCal


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ALPIDE – technology and layoutPixel Sensor using TowerJazz 0.18 mm CMOS technology

Sensing diode readout

• Deep PWELL shields NWELL of PMOS transistors (full CMOS circuitry within pixel active area)

• Reverse bias voltage (-6 V < VBB < 0 V) to substrate (contact from the top) to increase depletion zone around NWELL collection diode

• Small n-well diode (2 mm diameter), ~100 times smaller than pixel => low capacitance (~fF)

• High-resistivity (> 1 kW cm) p-type epitaxial layer (25 mm) on p-type substrate

ze

ro

su

pp

ressio

n

ze

ro

su

pp

ressio

n

ze

ro

su

pp

ressio

n

zero

s

uppre

ssio

n

Buffering and Interface

TH

COMPAMP

In-pixel: • Amplification • Discrimination • 3-hit storage register (MEB) • In-matrix sparsification

continuousor

external trigger


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Lc+

• Lc+ accessible in Pb-Pb

• v2 can be measured at intermediate and high pT

• Large improvement also for D0 & DS+ signals, possibility to discriminate

hadronization models (thermal or coalescence hadronization)



38Zhongbao Yin@LHCP201720/5/2017

Documents

ALICE upgrade overview - Indico · 2018. 11. 21. · ITS IB Staves Module assembly machine sensors thinned to 50mm 9 chips, stave length ~450 mm for IB HIC for IB Positioning Stave