calcutta, 2.2005 j. schukraft1 the quest for the qgp: 20 years of heavy ion physics

Calcutta, 2.2005 J. Schukraft 1

The quest for the QGP:The quest for the QGP:20 years of heavy ion physics 20 years of heavy ion physics

The quest for the QGP:The quest for the QGP:20 years of heavy ion physics 20 years of heavy ion physics

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ExplorationsExplorationsSearch for the QGP* Search for a sea passage to India*

world map, late 15th centuryQCD map, late 20th century

A Mid-Fifteenth-Century European World Map (1466)The Mediterranean basin, known to Ptolemy and later Europeans, is fairly accurately depicted, but the Eastern portions of the map are very incomplete since they were based on often-fictitious travelers’ accounts rather than observation. *Original idea from H. Satz and D. Karzheev, Hard probes WS, Portugal, 2004

https://webh04.cern.ch/event-hardprobes04/

http://www3.newberry.org/k12maps/module_01/map/core.html

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ExplorersExplorers

‘In 1493, Columbus wrote a brief report concerning his discoveries of "Islands of India beyond the Ganges." It was intended as a public notice to announce his discoveries and to garner support for another voyage. The first edition of this letter was printed in Spanish in Barcelona in April 1493.’ Quote from US library of Congress

Columbus: visionary, enthusiastic adventurer

Not afraid to venture far into the unknown

with little guidance and marginal preparation.

As befits the brave (and lucky), he made a

BIG discovery.

Headline Barcelona News

April 1493

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ExplorersExplorers

Vasco da Gama: methodical explorer

Building on years of systematic ‘experimental’

discoveries, one step at a time..

As befits the diligent, he reached his goal in due time

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For the last leg, VdG was guided

by an Indian pilot, arranged for by

Ahmed ibn Majid in Malindi.

Thomas Kostecki, Vasco da Gama (1998)

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2020thth Century Explorers Century Explorers

Hans, the visionary adventurer Louis, the systematic explorer Bikash, the Indian pilot

Lessons from the 15th century:

- there are different approaches to make a discovery

-you don’t always findwhat you set out to discover

- when venturing into the unknown, have the Indians ‘on board’

India: Strong and recognized partner in quest for QGP

- > 60 physicists, > 8 Institutes

- participation in SPS, RHIC and LHC programs

- 5th largest nation in ALICE

- strong Theory community

Calcutta 2005 J. Schukraft

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What are we looking for ?What are we looking for ?

NA35 streamer chamber picture, ca 1990Da Gama arriving in India, 1498

15th century explorers:

direct trade route to the

‘Origin of Spices’

20th century explorers:

understanding the

‘Origins of Matter’

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QGP: The ‘Original’ State of MatterQGP: The ‘Original’ State of Matter

QGP = true ground state of QCD melting matter => deconfinement study phase diagram of matter melting vaccum (gluon condensate)

=>chiral symmetry restoration

dynamical origin of constituent mass

Phase transitions involving elementary quantum fields

phase transitions and spontaneous symmetry breaking central to HEP

QCD transition is the only one accessible dynamically

Cosmology & Astrophysics early Universe at ~ 1 s interior of neutron stars

new domain of hot & dense QCD surprises ?

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Melting MatterMelting Matter

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Elementary Particles 0.1% 12 matter particles (quarks, leptons)

only 4 relevant today (u, d, e, ) 13 force particles (3 massive, 10 massless)

Composite Particles (hadrons) 4% hundreds…

only 2 are relevant (p,n), making nuclei

What stuff is the Universe made of ??

We don’t know how and why for ~ 5%

We don’t even know what for the other 95%

Dark Matter 23% made of unknown particles

Dark Energy 73% vacuum energy

of completely unknown origin should be infinite or exactly 0

The Dark Mystery of Matter The Dark Mystery of Matter

SM Higgs mechanism QCD chiral symmetry breaking

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Recent Lattice QCD ‘Maps’Recent Lattice QCD ‘Maps’ recent progress

improved actions improved symmetries larger lattices

crit. temperature energy density EOS

Tc ~ 175 ± 8 ± 8 MeV

c ~ (6±2) Tc4

(-3P) 0

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t = - 3 fm/c t = 0 t = 1 fm/c t = 5 fm/c

t = 10 fm/ct = 40 fm/c

Heavy Ion CollisionHeavy Ion Collision

hard collisions pre-equilibrium QGP

hadron gas

freeze-out


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Experimental FacilitiesExperimental Facilities AGS (1986 - 1998)

Beam: Elab < 15 GeV/N, s ~ 4 GeV/N Users: 400 Experiments: 4 big, several small

SPS (1986 - 2003) Beam: Elab < 200 GeV/N, s < 20 GeV/N Users: 600 Experiments: 6-7 big, several small

RHIC (>2000) Beam: s < 200 GeV/N Users: 1000 Experiments: 2 big, 2 small

LHC (>2007) Beam: s < 5500 GeV/N Users: 1000 Experiments: 1 dedicated HI, 3 pp expts

X 5

X 10

X 30

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Roadmap, 3rd ICPA-QGP

Jaipur, March 1997

large systems thousand of particles Volume > 4000 fm3

energy density up to 3 GeV/fm3

strongly interacting system hadronic rescattering collective phenomena (flow) thermal particle ratios f(T, )

signs of ‘new state of matter’ e+e- pairs (chiral symmetry rest. ?) J/ suppression (deconfinement ?)

Very complex reactions

can be measured

and analyzed


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Soft Probes: Elliptic FlowSoft Probes: Elliptic Flow Flow: Correlation between coordinate and momentum space

close particles move at similar velocity and direction flow builds up in an interacting medium with pressure gradients for given boundary conditions, flow profile depends on

Equation of State EoS and viscosity of ‘fluid’ Hydrodynamics of perfect fluid: = 0, = 0 (‘strongly interacting’)

px > py

Elliptic Flow reduces spatialElliptic Flow reduces spatial

anisotropy -> acts at early timesanisotropy -> acts at early times


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First Flow Measurement at SPSFirst Flow Measurement at SPS

WA93/98 PMD detectors measures

azimuthal anisotropy of photonsPresented by Indian group (Y. Viyogi) at QM’95

Particle emission

is correlated !

Implications:Implications: strongly interacting ‘matter’ collective expansion ~1/2 ideal hydrodynamics

Remember Columbus:

-Elliptic Flow not expected at SPS

-PMD meant to look for photon/hadron fluctuations (Centauro like events), discovered flow instead

http://www.veccal.ernet.in/~pmd/WA98/pmd.jpg


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Photons: Thermal Photons: Thermal Radiation ?Radiation ?

Thermal photons ‘heat’ radiation from initial hot phase

‘El Dorado’ of QGP physics

rate ~ T4 => sensitive to early phase rate ~ lifetime => contribution from hadronic phase

very challenging measurement high pt: direct QCD hard scattering medium pt: 0 decay photons finally sighted at very low pt ???

Subtraction method,upper limit

Correlation method:

Subtraction method

Predictions

hadronic gasQGP

sumpQCD

Most probable yield (Ro=6 fm)The lowest yield (Ro=0)

WA98

QM 2004

CERN Press release in 2000 on ‘Evidence for new state of matter’‘It is expected that the present "proof by circumstantial evidence" for the existence of a quark-gluon plasma in high energy heavy ion collisions will be further substantiated by more direct measurements (e.g. electromagnetic signals which are emitted directly from the quarks in the QGP) ...’


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Hard Probes: J/Psi suppressionHard Probes: J/Psi suppression

cc c

c

c

c

beams of hard probes:jets, J/ ….

normalmatter

QGP

Perturbative Vacuum

cc

Color Screening

cc

Onset of Deconfinement ?

Ca 1986


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NA44

NA49/Ceres

SPS ExperimentsSPS Experiments

NA49

NA50

Radial expansion, ‘Hubble Flow’

Deconfinementmass generation

Thermal particle ratios f(,T)’


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The Relativistic Heavy Ion Collider

Current hunting ground for Quark Gluon Plasma


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RHIC ExperimentsRHIC ExperimentsSTAR

PHENIX

PHOBOSBRAHMS

small angle particles Particle Production

parton energy loss

Elliptic Flow


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Flow at RHICFlow at RHIC

12 , tan ( )cos 2( ) y

xrv

p

p

3 2

31

11 2 cos

2 n rnt t

d N d NE v nd p p dp dy

py

px

Momentum space

matter at RHIC: ~ perfect fluid with ~ zero mean free path ! huge effect (almost 2:1 at high pt) almost perfect agreement with hydro f(impact parameter, pt, particle mass)

STAR PRL 86, (2001) 402

|| < 1.3

0.1 < pt < 2.0


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peripheral

Hard Probes : Jet QuenchingHard Probes : Jet Quenching

hadrons

q

q

hadrons

leading particle NOTsuppressed

leadingparticle NOT suppressed

high pt partons: Vacuum: fragment into hadrons => JETS Matter: additional scattering => more gluon radiation

normal ‘cold’ matter: small effect QGP: strong effect (up to several 10 GeV)

observables of ‘jet quenching’ leading parton looses energy energy shows up in soft partons around jet axis

beams of hard probes:jets, J/ ….

Vacuum

QGP

central

jet quenching measures

‘radiation ‘ length of QGP

dE ~ D2 x L2

D = Debye screening mass


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India or America ?India or America ? SPS/AGS: ‘new state of matter’

solid evidence for collective, thermal hadronic matter new effects: quarkonia suppression & low mass lepton pair spectrum

RHIC: dense (thermalized ?) partonic matter elliptic flow compatible with hydrodynamical limit

Hydro = limit of zero mean-free-path => strongly interacting fluid, gas ! almost ideal fluid, /s ~ 0.1 (much better than water !)

jet quenching compatible with complete absorption from interior strength of interaction seems mysteriously high


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RHIC

QCD, early 21st century

QG-Plasma or QG-Molasses ?QG-Plasma or QG-Molasses ? QGP: weakly interacting ‘gas’ of quarks and gluons

deconfined, chiral symmetry restored

sQGP: strongly interacting partonic fluid

Columbus: ‘Having now accomplished the undertaking upon which I set out,…

I advanced forward, thinking that I could find some town - but at length, perceiving that nothing new was likely to appear - I determined to make no further search.’

The journey must go on !The journey must go on !

QCD map, late 20th century


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The Large Hadron Collider

Future place for studying the Quark Gluon Plasma


27ALICE Set-upALICE Set-up

HMPID

Muon Arm

TRD

PHOS

PMD

ITS

TOF

TPC

Size: 16 x 26 m

Weight: 10,000 tons


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ALICE CollaborationALICE Collaboration

UKPORTUGAL

JINR

GERMANY

SWEDENCZECH REP.

HUNGARYNORWAY

SLOVAKIAPOLANDNETHERLANDS

GREECE

DENMARKFINLAND

SWITZERLAND

RUSSIA CERN

FRANCE

MEXICOCROATIA ROMANIA

CHINA

USAARMENIA

UKRAINE

INDIA

ITALYS. KOREA

~ 1000 Members

(63% from CERN MS)

~30 Countries

~80 Institutes

0

200

400

600

800

1000

1200

1990 1992 1994 1996 1998 2000 2002 2004

ALICE Collaboration statistics

LoI

MoU

TP

TRD


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The ALICEThe ALICE Magnet: Magnet:

ready for the experiment to move in!ready for the experiment to move in!


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Inside the ALICE TPC


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India in AliceIndia in AlicePMD prototype

Manas electronics chip

Muon Chamber


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RHIC

Past-Present-Past-Present-FutureFuture

AGS/SPS: 1986 – 1994AGS/SPS: 1986 – 1994 existence & properties of hadronic phase

chemical & thermal freeze-out, collective flow,…

SPS: 1994 – 2003SPS: 1994 – 2003 ‘compelling evidence for new state of matter with many properties predicted for QGP’

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

RHIC: 2000 - ?RHIC: 2000 - ? compelling evidence -> establishing the (s)QGP ?

parton flow, parton energy loss

LHC: 2007 - ??LHC: 2007 - ?? ‘go west’ or find the ‘Island of India beyond the Ganges’ precision spectroscopy of ‘ideal plasma ‘QGP

heavy quarks (c,b), Jets, Y, thermal photons

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We are on an exciting and wondrous exploration,

not taking any chances:

We have the Indian pilot and his crew ‘on board’

calcutta, 2.2005 j. schukraft1 the quest for the qgp: 20 years of heavy ion physics

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