Apr 18, 2023 Jan Rak, HEP 2007 1

Heavy Ion Heavy Ion PhysicsPhysics

Experimental Experimental Overview Overview

Heavy Ion Heavy Ion PhysicsPhysics

Experimental Experimental Overview Overview Jan RakJan Rak

Jyväskylä University & Helsinki Institute of Physics, Finland

Experimentalist point of viewExperimentalist point of view Experimentalist point of viewExperimentalist point of view

Apr 18, 2023 Jan Rak, HEP 2007 2

Heavy Ion Heavy Ion PhysicsPhysics1980-2004 old 1980-2004 old paradigmparadigm

Heavy Ion Heavy Ion PhysicsPhysics1980-2004 old 1980-2004 old paradigmparadigm Exploring Exploring PhasesPhases and and StructuresStructures of of QCD QCD phase phase diagramdiagram

– High temperatureHigh temperature TT

– High densityHigh density

– Many-body aspectsMany-body aspects QCDQCD

– Vacuum propertiesVacuum properties

RHIC

LHC

hot & dense & net

baryon free

q

q

q

q

q

qq

q

q

q

q

qq

qq

q

qq

qq

q

q

qq

q

q q

q

qq

qq

q

q

q

q

q

q

q

q

qqq

qqq

qqq

qqq

q q

qq

Apr 18, 2023 Jan Rak, HEP 2007 3

Heavy Ion Heavy Ion PhysicsPhysics20052005 new new paradigmparadigm

Heavy Ion Heavy Ion PhysicsPhysics20052005 new new paradigmparadigm Heavy Ion - test laboratory for string theory

• Shear viscosity “Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics” P.K. Kovtun, D.T. Son, and A.O. Starinets

•Quenching parameter “Calculating the jet quenching parameter from AdS/CFT” Liu, Rajagopal, and Wiedemann

• Thermal particle production Unruh mechanism, Karzeev, Satz

Robi Peschanski parallel talk on Thursday

Apr 18, 2023 Jan Rak, HEP 2007 4

Phase transition in Heavy Ion Phase transition in Heavy Ion collisionscollisions

Phase transition in Heavy Ion Phase transition in Heavy Ion collisionscollisions

T.D.Lee (1974) Temporarily restored broken symmetries of the physical vacuum

Collins, Perry (1975) Asymptotic freedom in QCD deconfined quarks/gluons matter

E.V. Shuryak (1978) Invented Quark Gluon Plasma target of HI community

0.2 fm 0.02 fm 0.002 fm

strong coupling

S(Q

)

Infrared Slavery

Asymptotic Freedom T = 150-200 MeV ~ 0.6-1.8 GeV/fm3

T = 150-200 MeV ~ 0.6-1.8 GeV/fm3

Lattice QCD, Lect. Notes Phys 583, 209 (2002)

Ideal gas limit

Apr 18, 2023 Jan Rak, HEP 2007 5

HI - Center Of Mass Energy regimesHI - Center Of Mass Energy regimes HI - Center Of Mass Energy regimesHI - Center Of Mass Energy regimes

80s AGS s4 GeV USA80s AGS s4 GeV USA

90s SPS s17 GeV CERN90s SPS s17 GeV CERN4x

2000 RHIC s200 GeV USA

2000 RHIC s200 GeV USA

11x

8x

2008 LHC pp s14 TeV

2008 LHC pp s14 TeV

2008 LHC AA s5.5 TeV CERN2008 LHC AA s5.5 TeV CERN27x

Relativistic Heavy Ion Collider

Brookhaven Nat. Lab. Long Island, USA

SPS era: Smoking gun

wanted

RHIC era: sQGP

discovered

LHC era:

?

Apr 18, 2023 Jan Rak, HEP 2007 6

HI collision - Nuclear Modification HI collision - Nuclear Modification Factor Factor RRAAAA

HI collision - Nuclear Modification HI collision - Nuclear Modification Factor Factor RRAAAA

RAA (pT ) =d2NAA / dpTdη

Nbinary d2Npp / dpTdηRAA (pT ) =

d2NAA / dpTdηNbinary d2Npp / dpTdη

A+AA+A

n x m Nbinary

varies with impact parameter b

p+pp+p

Apr 18, 2023 Jan Rak, HEP 2007 7

SPS SPS s = 17 GeV RHIC s = 17 GeV RHIC s = 200 s = 200 oo datadata

SPS SPS s = 17 GeV RHIC s = 17 GeV RHIC s = 200 s = 200 oo datadata

s=17 GeV

s=17 GeV

Although there were hints for anomalous behavior of nuclear matter at SPS (see CERN press. Rel. 2000)

J/ supp., dilepton enhanc., prompt

No light pion suppression observed.

No light pion suppression observed.

Apr 18, 2023 Jan Rak, HEP 2007 8

p-p collisions at RHIC: p-p collisions at RHIC: 00 production (PHENIX) production (PHENIX)

p-p collisions at RHIC: p-p collisions at RHIC: 00 production (PHENIX) production (PHENIX)

19% norm uncertainty

€

e−5.6pT

NLO pQCD agrees with dataNLO pQCD agrees with data

arXiv:0704.3599v1 [hep-ex]

Phys. Rev. Lett., 2006, 97, 252001s=200GeV

Apr 18, 2023 Jan Rak, HEP 2007 9

0

0

RHIC RHIC s = 200 s = 200 oo and h and h+++h+h-- data dataRHIC RHIC s = 200 s = 200 oo and h and h+++h+h-- data data

dAu

0

• Strong suppression (x5) in central Au+Au coll.

• No suppression in peripheral Au+Au coll.

• No suppression (Cronin enhancement) in control d+Au exp.

Convincing evidence for the final state partonic interaction - emergence of sQGP

• Strong suppression (x5) in central Au+Au coll.

• No suppression in peripheral Au+Au coll.

• No suppression (Cronin enhancement) in control d+Au exp.

Convincing evidence for the final state partonic interaction - emergence of sQGP

Apr 18, 2023 Jan Rak, HEP 2007 10

QQCCD and Jets D and Jets QQCCD and Jets D and Jets

•At the famous Snowmass conf. (July 1982) almost nobody believed that jets seen in e+e collisions exist also in p+p. NA5 data - no jet structure.

•The International HEP conference in Paris, three weeks later, changed everything.

C. DeMarzo et al NA5, PLB112(1982)173

Full azim. trigg.

b-2-b trigg.

QCD

This one event from UA2 in 1982 changed everybody’s

opinion.

This one event from UA2 in 1982 changed everybody’s

opinion.

Apr 18, 2023 Jan Rak, HEP 2007 11

Status of RStatus of RAAAA in AuAu at in AuAu at ssNNNN=200 GeV=200 GeVStatus of RStatus of RAAAA in AuAu at in AuAu at ssNNNN=200 GeV=200 GeV

Direct are not suppressed. 0 and η suppressed even at high pT

Implies a strong medium effect (energy loss) since not affected. Suppression is flat at high pT.

Direct are not suppressed. 0 and η suppressed even at high pT

Implies a strong medium effect (energy loss) since not affected. Suppression is flat at high pT.

Apr 18, 2023 Jan Rak, HEP 2007 12

For Au+Au min bias direct For Au+Au min bias direct R RAAAA is is simplesimple

For Au+Au min bias direct For Au+Au min bias direct R RAAAA is is simplesimple

Au+Au minimum bias at mid-rapidity

Do the structure function ratios actually drop by ~20% from x=0.1 to x=0.2?

Do the structure function ratios actually drop by ~20% from x=0.1 to x=0.2?

Eskola,Kolhinen,Ruuskanen Nucl. Phys. B535(1998)351

100 xT

x

Eskola et al. NPA696 (2001) 729

gluons in Pb / gluons in p

AntiShadowing

Shadowing

Apr 18, 2023 Jan Rak, HEP 2007 13

The biggest result at QM2006?The biggest result at QM2006?The biggest result at QM2006?The biggest result at QM2006?

If RAA= R

AA the whole concept of energy loss changes: perhaps no

effect for pT>20 GeV. New physics on the horizon?

If RAA= R

AA the whole concept of energy loss changes: perhaps no

effect for pT>20 GeV. New physics on the horizon?

p+p+X reference

From FNAL, SPS, ISR extrapolation our own measurement

Apr 18, 2023 Jan Rak, HEP 2007 14

More cracks in the ice ? More cracks in the ice ? More cracks in the ice ? More cracks in the ice ?

J/

heavy quarks

Apr 18, 2023 Jan Rak, HEP 2007 15

J/J/ Suppression--R Suppression--RAAAA

PHENIX mid-rapidity (e+e-) the same as PHENIX mid-rapidity (e+e-) the same as NA50!!!NA50!!!

J/J/ Suppression--R Suppression--RAAAA

PHENIX mid-rapidity (e+e-) the same as PHENIX mid-rapidity (e+e-) the same as NA50!!!NA50!!!

NA50 at SPS (0<y<1)PHENIX at RHIC (|y|<0.35)

Suppression increases at more forward rapidity PHENIX PRL 98,

232301 (2007)

Color Screening

cc

Less dense medium

More dense medium

Apr 18, 2023 Jan Rak, HEP 2007 16

Heavy quarks as a probe Heavy quarks as a probe

•Due to large mass heavy quarks are primarily produced by gluon fusion sensitive to initial gluon distribution M. Gyulassy and Z. Lin, PRC 51, 2177 (1995)

• Heavy quarks lose less energy due to suppression of small angle gluon radiation (dead-cone effect) Dokshitzer and Kharzeev, PLB 519, 199 (2001)

parton

hot and dense medium

light

M.Djordjevic PRL 94 (2004)

ENERGY LOSS

Phys.Rev.Lett.98:172301,2007

J. Bielcik Thursday parallel pres.

Apr 18, 2023 Jan Rak, HEP 2007 17

Inclusive probes summaryInclusive probes summaryInclusive probes summaryInclusive probes summaryWe observed:

• Huge suppression of light mesons in central Au+Au collisions

• No suppression in d+Au and peripheral Au+Au coll.

• Similar suppression of J/ at RHIC as at SPS

• Similar suppression for heavy and light quarks

Concluded:

Deconfined opaque partonic matter has been produced.

Let’s look at more dynamical observables

azimuthal anisotropy of produced hadrons (Flow)

Apr 18, 2023 Jan Rak, HEP 2007 18

Nuclear Geometry and Hydrodynamic Nuclear Geometry and Hydrodynamic flowflow

Nuclear Geometry and Hydrodynamic Nuclear Geometry and Hydrodynamic flowflow

RP

multiple scattering

larger pressure gradient in plane

d 3N

pTdpTdyd∝ [1+ 2v2 (pT )cos2( −φRP ) + ...]

d 3N

pTdpTdyd∝ [1+ 2v2 (pT )cos2( −φRP ) + ...]

less yield out

more in plane

less yield out

more in plane x

yz

Reaction Plane

Spatial asymmetry eccentricity

=y2 − x2

y2 + x2

Mom. Asymmetry elliptic

flowv2 =

px2 − px

2

px2 + px

2

Apr 18, 2023 Jan Rak, HEP 2007 19

v2

baryons

mesons

““Fine structureFine structure” of ” of v2(pT) for different mass v2(pT) for different mass particles. particles. In Ideal “hydro” picture:In Ideal “hydro” picture:

What are the relevent DOF’s in What are the relevent DOF’s in “Flow” ?“Flow” ?

What are the relevent DOF’s in What are the relevent DOF’s in “Flow” ?“Flow” ?

v2(KET) universal for baryons

v2(KET) universal for mesons

Do we have an even more universal scaling?Do we have an even more universal scaling?

∂νTμν = 0 → Work-energy theorem

→ ∇PdVvol∫ = ΔEK =

= mT − m0 ≡ ΔKET

∂νTμν = 0 → Work-energy theorem

→ ∇PdVvol∫ = ΔEK =

= mT − m0 ≡ ΔKET

v2(pT) v2(KET)

Phys. Rev. Lett., 2007, 98, 162301

Apr 18, 2023 Jan Rak, HEP 2007 20

QG medium fragmentation-QG medium fragmentation-quark quark recombinationrecombination

QG medium fragmentation-QG medium fragmentation-quark quark recombinationrecombination

dVPS

quarks

pt

3 quarks

1 proton

Why is the universal v2(KET) different for meson and baryons?

Exited quark-gluon medium huge phase-space densities constituent Quark Recombination /

Coalescence Phys. Lett.,1996,B371,157-162 FERMILAB hep-ex/9601001

(xF ) =D− (cd) − D+ (cd )

D− + D+

Phys.Rev.Lett.91:092301,2003

v2meson (pT ) ≈2⋅v2

quark pT ,quark

2⎛⎝⎜

⎞⎠⎟ v2

baryon(pT ) ≈3⋅v3quark pT ,quark

3⎛⎝⎜

⎞⎠⎟

v2meson (pT ) ≈2⋅v2

quark pT ,quark

2⎛⎝⎜

⎞⎠⎟ v2

baryon(pT ) ≈3⋅v3quark pT ,quark

3⎛⎝⎜

⎞⎠⎟

dN

d=[1+ 2v2 (pT )cos2 ]

dN

d=[1+ 2v2 (pT )cos2 ]

cos2 =12

dNd

cos(2 )d0

2

∫ =v2

meson: 12

dNd

⎛⎝⎜

⎞⎠⎟

2

cos(2 )d0

2

∫ =2v2

baryon: 12

dNd

⎛⎝⎜

⎞⎠⎟

3

cos(2 )d0

2

∫ =3v2 +Θ(v23 )

cos2 =12

dNd

cos(2 )d0

2

∫ =v2

meson: 12

dNd

⎛⎝⎜

⎞⎠⎟

2

cos(2 )d0

2

∫ =2v2

baryon: 12

dNd

⎛⎝⎜

⎞⎠⎟

3

cos(2 )d0

2

∫ =3v2 +Θ(v23 )

Apr 18, 2023 Jan Rak, HEP 2007 21

v2

0.1

0.05

0

v2 /nq

The “Flow” Knows QuarksThe “Flow” Knows QuarksThe “Flow” Knows QuarksThe “Flow” Knows Quarks

v2 (pT ) → nq ⋅v2

KET

nq

⎛

⎝⎜

⎞

⎠⎟

v2 (pT ) → nq ⋅v2

KET

nq

⎛

⎝⎜

⎞

⎠⎟

Assumption:

all bulk particles are coming from recombination of flowing partons

Discovery of universal scaling:

● flow parameters scaled by quark content nq resolves meson-baryon separation of final state hadrons. Works for strange and even charm quarks. ● strongly suggests the early thermalization and quark degree of freedom.

Apr 18, 2023 Jan Rak, HEP 2007 22

Jet shape evolution with trigger and Jet shape evolution with trigger and assoc. assoc. ppTT

Jet shape evolution with trigger and Jet shape evolution with trigger and assoc. assoc. ppTTAu+Au / p+p s = 200 GeV

arXiv:0705.3238 [nucl-ex]

Per-trigger yield vs. for various trigger and partner pT (pA

T pBT), arranged by

increasing pair momentum (pAT + pB

T)

d+Au

p + p jet + jet

Apr 18, 2023 Jan Rak, HEP 2007 23

Is the quark matter really perfect Is the quark matter really perfect fluid? fluid?

Is the quark matter really perfect Is the quark matter really perfect fluid? fluid?

Viscosity η then defined as . In the standard picture

reflects the transport properties of multi-particle system. small viscosity → Large cross sectionsLarge cross sections → strong couplingsStrong couplings → perturbation theory difficult !

Fx

Area=η

∂vx

∂y

Ideal fluid η=0Ideal fluid η=0

String theory approach:

Strongly interacting matter AdS/CFT duality

(Phys. Rev. Lett., 2005, 94, 111601)

What can we learn from the data ?

ηs

≥1

4π

Apr 18, 2023 Jan Rak, HEP 2007 24

Viscosity from the data at RHICViscosity from the data at RHICViscosity from the data at RHICViscosity from the data at RHIC

Phys. Rev., 2003, C68, 034913 Phys. Rev. Lett., 2007, 98, 092301

ηs

/1

4π: 1.13 ± 0.18

ηs

/1

4π: 1.13 ± 0.18

Temperature

T=160 MeV

Mean free path (transport sim.)

f=0.30.03 fm

Speed of sound

cs=0.350.05

ηs

= Tλ f csηs

= Tλ f cs

Apr 18, 2023 Jan Rak, HEP 2007 25

Jet Quenching: AdS/CFT Jet Quenching: AdS/CFT or or pQCD ?pQCD ? Jet Quenching: AdS/CFT Jet Quenching: AdS/CFT or or pQCD ?pQCD ?“Testing AdS/CFT Deviations from pQCD Heavy Quark Energy Loss with Pb+Pb at LHC 2007

“Horowitz Gyulassy arXiv:0706.2336

RAA ≈ 1−(pT )( )n(pT )RAA ≈ 1−(pT )( )

n(pT )Energy loss :

1. pQCD fractional momentum loss for Heavy Quark:

Djordjevic, Gyulassy Nucl.Phys.A733:265-298,2004

pQCD ≈ Cα S3 dNg

dy

L

A⊥

log(p⊥ / MQ )

p⊥ pQCD ≈ Cα S

3 dNg

dy

L

A⊥

log(p⊥ / MQ )

p⊥

d logPzdτ

≡μ =T 2

2MQ

d logPzdτ

≡μ =T 2

2MQAdS ≈ 1− exp μ (τ )

τ 0

L

∫⎡⎣⎢⎤⎦⎥

AdS ≈ 1− exp μ (τ )τ 0

L

∫⎡⎣⎢⎤⎦⎥

– independent of pT ans stronger dependence on MQ !

–T2 dependence in exponent makes for a very sensitive probe

–Expectation: pQCD0 at high pT vs AdS is independent of pT!

2. String theory momentum loss for Heavy Quark: Gubser, Herzog et al

Apr 18, 2023 Jan Rak, HEP 2007 26

AdS/CFT AdS/CFT and and pQCD at LHCpQCD at LHCAdS/CFT AdS/CFT and and pQCD at LHCpQCD at LHC

LHC is the D and B factory - should and will be easy to measure!

LHC is the D and B factory - should and will be easy to measure!

Double ratio of charm and bottom quark suppression

promising window for AdS/CFT models. pQCD ≈ Cα S3 dNg

dy

L

A⊥

log(p⊥ / MQ )

p⊥ pQCD ≈ Cα S

3 dNg

dy

L

A⊥

log(p⊥ / MQ )

p⊥

AdS ≈ 1− exp μ (τ )τ 0

L

∫⎡⎣⎢⎤⎦⎥

AdS ≈ 1− exp μ (τ )τ 0

L

∫⎡⎣⎢⎤⎦⎥

Apr 18, 2023 Jan Rak, HEP 2007 27

…..

Apr 18, 2023 Jan Rak, HEP 2007 28

SummarySummarySummarySummary

•RHIC provided us the high precision data which indicate: – High density deconfined matter is produced– Quark DOFs observed (v2 scaling) – Fast thermalization– Small viscosity (strongly coupled matter)

•Open questions:– Heavy and light quark suppression similarity– Prompt photon suppression at high-pT

– J/ suppression similar at RHIC (s=200GeV) and SPS (s=17GeV)

– J/ suppression at RHIC larger at forward rapidity

•New physics is under exploration– HI collisions provide a testbed for “applied string physics”

LHC data will be crucial for further exploration of new directions.

sQGP

Apr 18, 2023 Jan Rak, HEP 2007 29

PHENIX milestone: signal of chiral PHENIX milestone: signal of chiral dynamicsdynamics

PHENIX milestone: signal of chiral PHENIX milestone: signal of chiral dynamicsdynamics

Subm. to Phys. Rev. Lett

arXiv:0706.3034

symmetry broken

quark condenste 250 MeV3

symmetry restored Brown-Rho

quark condenste 0 MeV3

Rulled out

NA60NA60

s=17 GeV

Apr 18, 2023 Jan Rak, HEP 2007 30

55thth PHENIX milestone: signal of chiral dynamics PHENIX milestone: signal of chiral dynamics55thth PHENIX milestone: signal of chiral dynamics PHENIX milestone: signal of chiral dynamics

Subm. to Phys. Rev. Lett

arXiv:0706.3034

low mass dilepton excess at RHIC!

yield grows faster than Npart

excess > r modification

symmetry broken

quark condenste 250 MeV3

symmetry restored Brown-Rho

quark condenste 0 MeV3

Rulled out

Apr 18, 2023 Jan Rak, HEP 2007 31

Comparison: Comparison: ρρ mass modificationmass modificationComparison: Comparison: ρρ mass modificationmass modification

R.Rapp, Phys.Lett. B 473 (2000)R.Rapp, Phys.Rev.C 63 (2001)R.Rapp, nucl/th/0204003

calculations for min bias QGP

thermal radiation included

Broad range enhancement

150 < mee < 750

MeV3.4±0.2(stat.)

±1.3(syst.)±0.7(model)submitted to Phys. Rev. Lett

arXiv:0706.3034