The Quest for the Quark-Gluon-Plasma: The High-Energy Frontier

• Why Heavy Ions at the LHC?

• Where we stand• What lies ahead

Paolo GiubellinoINFN Torino

Paris Nov 2004

The Relativistic Heavy Ion ColliderAt Brookhaven National Laboratory

At the moment the hunting ground for the Quark Gluon Plasma is across the Ocean …

The Large Hadron Collider

… But the future place for studying the Quark Gluon Plasma is back in Europe!

Nuclear accelerators• The LHC latest of a

series of successful accelerators– After many problems have been

overcome, both technical and financial, startup is foreseen for 2007, with first HI run in 2008

/ 2007

(transparency from H. Specht, 1992)

Heavy-Ion Physics @ LHC

~1100 participants: (~two thirds from

NUPECC countries)

1000 ALICE 60 CMS 25 ATLAS

A large community which has been constantly growing over the years, and still grows! => VERY lively field!!!

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1990 1992 1994 1996 1998 2000 2002 2004

ALICE

Collaboration statistics

LoI

MoU

TP

TRD

SOUTH AFRICA

UK

PORTUGAL

JINR

GERMANY

SWEDEN

CZECH REP.

HUNGARYNORWAY

SLOVAKIA

POLANDNETHERLANDS

GREECEDENMARK

FINLAND

SWITZERLAND

RUSSIA CERN

FRANCE

MEXICOCROATIA

ROMANIA

CHINA

USA

ARMENIA

UKRAINE

INDIA

ITALY

S. KOREA

Past/Present/Future of the high-energy frontier• AGS/SPS: 1986 – 1994

– existence & properties of hadronic phase, proof of principle of the method• chemical & thermal freeze-out, collective flow,…

• SPS: 1994 – 2003 (new results just coming: NA60)– Building a coherent picture. 'compelling evidence' for new state of matter with many properties predicted for QGP

• J/Y suppression (deconfinement ?)• low mass lepton pairs (chiral restoration ?)

• RHIC: 2000 - ?– compelling evidence -> establishing the QGP ?

• parton flow, parton energy loss Huge flux of results, tens of papers!– however: soft ~ semihard; lifetime hadron ~ parton phase

• LHC: 2007 - ?? (typ. > 10 yrs, see CDF)– (semi)hard >> soft, lifetime parton >> hadron phase– precision spectroscopy of ‘ideal plasma ‘QGP

• heavy quarks (c,b) Both Quarkonia and Open Charm & Beauty, Jets, Y, thermal photons

LHC: will open the next chapter in HI physics

significant step over & above existing facilities

THETHE place to do frontline research after 2007

Jet properties

Why at the LHC? - I Qualitatively new regime!

mu= md = ms

mu = md

mu = md ; ms mu,d

HQ suppressed exp(-mc,b,t/T)

Tc ~ ms

T well above Tc

Why at the LHC?-II Tools

• @LHC Hard processes contribute significantly to the total AA cross-section:– Bulk properties

dominated by hard processes;

– Very hard probes are abundantly produced.

• Weakly interacting probes become accessible.

LHC

RHIC

SPS

(h+

+h-)/20

17 GeV

200 GeV

5500 GeV=√s

LO p+p y=0

Hard probes have provided the most remarkable RHIC results: RAA dep. on PT, away-jet disappearance etc …

ALICE, with its tracking and PID is perfect for the task

Why at the LHC?-IIIHeavy Quarks

• Copiously produced• Y d/dy LHC ~ 20 x RHIC

• ALICE also measures B & D production => proper normalization!

Even

ts/1

00 M

eV

103

J/Y

5 10 15

102

dN/d=8000

M+- (GeV)

0

2.5 < < 4

c/b Quarkonia in ALICE 1 month statistics of PbPb √sNN=5.5 TeV

Y productionY production

RHICRHIC LHCLHC

R. Vogt, hep-ph/0205330

SPS RHIC LHC

√sNN (GeV) 17 200

dNch/dy 500 850

0QGP (fm/c) 1 0.2

T/Tc 1.1 1.9

(GeV/fm3) 3 5

QGP (fm/c) ≤2 2-4

f (fm/c) ~10 20-30

Vf(fm3) few 103 few 104 few 105

5500 X 28

1500-8000 ?

0.1 faster

3.0-4.2 hotter

15-60 denser

≥10longer

30-40

Quantitatively new regime!

Why at the LHC? - IV

Summary: ALICE Physics goals (have evolved along the years, to cover practically all relevant

observables) (in one experiment what at the SPS was done by 6-7 experiments, at RHIC by 4)

• Deconfinement: charmonium and bottonium spectroscopy•Chiral symmetry restoration: neutral to charged ratios, res. decays •Fluctuation phenomena - critical behavior: event-by-event particle comp. and spectra• Geometry of the emitting source: HBT, impact parameter via zero-degree energy flow• pp collisions in a new energy domain

Large acceptance Good tracking capabilities Selective triggering Excellent granularity

Wide momentum coverage P.I.D. of hadrons and leptons Good sec. vertex reconstr. Photon Detection

Use a variety of experimental techniques!

Global observables: Multiplicities, distributions

Degrees of freedom as a function of T hadron ratios and spectra, dilepton continuum, direct photons

Early state manifestation of collective effects: elliptic flow

Energy loss of partons in quark gluon plasma: jet quenching, high pt spectra, open charm and open beauty

ALICE central event

Nch(-0.5<<0.5)=8000

The ALICE Challenge!

Getting ready… ALICE represents an extraordinary expermental challenge

=> its preparation motivated many vigorous R&D programs

• In detector Hardware and VLSI Electronics => successfully completed across the decade of the 1990's:

– Inner Tracking System (ITS)• Silicon Pixels (RD19)• Silicon Drift (INFN/SDI)• Silicon Strips (double sided)• low mass, high density interconnects• low mass support/cooling

– TRD• radiators• bi-dimensional (time-space) read-out, on-chip • trigger (TRAP chip)

– TPC • gas mixtures (RD32)• advanced digital electronics• low mass field cage

– EM calorimeter• new scint. crystals (RD18)

– PID• Multigap RPC's (LAA)• solid photocathode RICH (RD26)

• In DAQ & Computing => in progress now– scalable architectures with

consumer electornics commercial components (COTS)

– high perf. storage media– GRID computing

Example: ITS Electronics Developments(all full-custom designs in rad. tol., 0.25 m process)

Pre

ampl

ifie

rs

Analoguememory

AD

Cs

ALICE PIXEL CHIP50 µm x 425 µm pixels 8192 cells Area: 12.8 x 13.6 mm2

13 million transistors ~100 µW/channel

ALICE SDD FEEPascal chip:64 channel preamp+ 256-deep analogue memory+ ADC Ambra chip:64 channel derandomizer chip

ALICE SSD FEEHAL25 chip:128 channelsPreamp+s/h+ serial out

And extreme lightweight interconnection techniques:

SSD tab-bondable Al hybrids

DOUBLE STACK OF 0.5 mm GLASS

Edge of active area

cathode pick up pad

cathode pick up pad

anode pick up pad

Resistive layer (cathode)

Resistive layer (cathode)

Resistive layer (anode)

Resistive layer (anode)

5 gaps

5 gaps

- 0.9 < < 0.9

full

for , K, p PID , K for p <2 GeV/cp for p <4 GeV/c

full size TOF modules under test

Multigap Resistive Plate Chambers

Example:Time Of FlightBreakthrough after > 5

years of R&D

0 500 1000-500-1000

1200

1000

800

600

400

200

0

STRIP 10 H.V. +- 6 kV

Time with respect to timing scintillators [ps]

= 53 ps minus 30 ps jitter

of timing scintillator = 44 ps

En

trie

s/5

0 p

s

Typical time spectrum

150 kchann. over ~150 m2

ALICE LAYOUT: TRACKING (and

event characterization)Inner Tracking System (ITS):6 Si Layers (pixels, drift, strips)Vertex reconstruction, dE/dx-0.9<<0.9

ZDC (impact parameter)Forward Multiplicity DetectorsT0 detectors (event time)V0 detectors (trigger)

TPC

Tracking, dE/dx

-0.9<<0.9

TRD

Tracking and

High-Pt Trigger

-0.9<<0.9

ALICE LAYOUT: PID

TOF

PID (K,p,)

-0.9<<0.9

HMPID: High Momentum Particle Identification (, K, p)

• RICH

• Hard Probes

TRD

Identification of electrons (p>1 GeV/c)

-0.9<<0.9

MUON arm

• Dimuons and vector mesons

• 2.4 < < 4

ALICE LAYOUT: photons

PHOS: high-granularity, high-resolution detector

• PbWO4 crystals

• photons and neutral mesons

• -jet tagging

PMD: Photon Multiplicity Detector

• Preshower detector with fine granularity

• Coverage: 2.3< <3.5, 270 k channels

• E-by-E fluctuaction, DCC, flow

ALICE tracking can fully exploit the high pt

signals which will become accessible at the LHC, even at the highest multiplicities

10 100

pt (GeV/c)

50

p/p

(%

)

10

30

50

100GeV/c

ALICE PPR CERN/LHCC 2003-049

ALICE momentum resolution at high pt

ALICE PID performance

STAR open charm in dAuD0 K-+ reconstruction in ALICE

Search for thermal charm production

Signals which are just hints at RICH becomes tools at the LHC: need Luminosity and the higher cross-section given by the higher Energy!

Example of the power of ALICE tracking + PID + vertexing

Getting ready …

• The infrastructure is taking shape

• All detectors are now in full construction phase– About 2/3 of ALICE construction budget has been spent

– Major construction, test, integration and commissioning effort, putting the facilities and the technical and scientific staff of all the ~80 ALICE laboratories under enormous stress

• A prolonged effort is ongoing, requiring an amazing cohesion and commitment from the collaborators … and a lot of support from their institutions:

• 2003, 2004, 2005, and part of 2006: construction

• 2006 and part of 2007: final integration and commissioning, while deploying the tools for DAQ and data analysis

The ALICE Magnet:

ready for the experiment to move in!

• still largest magnet– magnet volume: 12 m long, 12 m high– 0.5 T solenoidal field

The Space Frame …

Muon Magnet

0.7 T and 3Tm

4 MW power, 800 tons

World’s largest warm dipole

TPC Field Cage

TPC R/O chambers

• production finished in Bratislava and GSI

Muon Chambers Station 3-4: Slats

Trigger RPC

Station 1&2: Quadrants

ITS modules

• Now being produced in series….

Pixel

Strip

Drift

And a lot more… (just very few examples!)

TRD stack under test

Muon trigger chamber

PHOS PbWO4 Crystals

ZDC

V0 Prototype

ALICE DC III

Computing Phase Transition

– Online: storing up to 1.2 Gbyte/s

• whole WWW in few hours on tape !

• ~ 10 x RHIC !

– Offline: ~22 MegaSI2000

• 22000 PC's in 2004 (2800 Mhz)

• ~6 PB on disk per year

– cheap mass market components Industry & Moore's law

– make 100,000 mice do the work of one elephant: new computing paradigm:

The GRID

The Problem:

The Answer:

The Challenge:

ALICE features the Largest Grid in operation: for ALICE Distributed computing with GRID tools is already a reality!

40 centres in three continents, 7000 CPU’s, 100TB of storage In operation in the last 9 months

1 million jobs 500 MSI2k hours CPU (one PC for 60 years!)200 TB transferred from CERN

Next challenge: distributed data

analysis, using ALICE

E2E analysis prototype

end endto

UI applicationmiddlewareshell

Getting ready… But a lot remains to be done!• Some crucial items will come after 2007 and/or have still non-

confirmed funding :– DAQ (100% bandwidth foreseen for 2008)– High Level Trigger– Remaining 40% of TRD (recommended already at time of approval in Jan 2002

by the LHCC)– The 5 PHOS modules will come

• The first three one per year in 2006/7/8• The last two only if more funds are available

• The GRID progresses, yet the huge resources in hardware, software and system management needed for the offline must still be secured.

• Even later: Large-Acceptance EMcal for jets (proposed by a collaboration of 13 US institutions)

• ALICE at startup will not be fully equipped for hard Physics => OK since soft Physics will be addressed first (Luminosity will grow with time). However, the full potential of ALICE can only be realized when the combined complementary information of all its detector systems will be available.