Heavy Ions Collisions (results and questions)

11

Heavy Ions CollisionsHeavy Ions Collisions(results and questions)(results and questions)

Anatoly LitvinenkoElena Litvinenko

[email protected]@nf.jinr.ru

22

Outline.Outline.

Ядерная материя при большой плотности энергии Новое фазовое состояние – легко верится

Workshop on Heavy Ions, New York, Nov. 29 - Dec 1, 1974.

The name ”Quark Gluon Plasma” was coined by Eduard Shuryak in 1978.

33

The conception of the phase diagram of QCD as a function of time

L. McLerran and N. Samios

44

Ideal massless gas

Bosons -- 1- degree of freedom:

423

02

4

30π

=1ω

ωω

π1

=ε TT

dGeVB ∫∞

-)/exp()(

87

30π

=1+ω

ωω

π1

=ε 423

02

4 ∫∞

TT

dGeVF )/exp()(

Fermions -- 1- degree of freedom:

2 quarks

3 quarks

42

42

cscqs 30

π37

30

π)82

8

73222(ε TT

f=+=

42

42

cscqs 30

π47.5

30

π)82

8

73223(ε TT

f=+=

55

A few words about values

Bosons -- 1- degree of freedom:

34-

2

fm

GeV 0.034 102.7

30

π)( ⇒==ε 44

cB TGeV

3fm

GeV 0.03

8

7=ε⇒ε=ε FBF

Fermions -- 1- degree of freedom:

α=1=1= GeVac ][ ; ; 343 0.2/)ε(GeV)ε(GeV/fm fm 0.2

1== ⇒GeV

GeVTc 0.17=

2 quarks

3 quarks

)/(1.337 3

Bεε fmGeV==

)/(1.647.5 3

Bεε fmGeV==

66

Lattice QCD

GeVTc 0.17=

)/()(T/T1.3=ε c34 fmGeV

)/()(T/T1=ε c34 fmGeV

Frithjof Karsch, arXiv:hep-lat/0106019v2 (2001)

F. Karsch, Lecture Notes in Physics 583 (2002) 209.

7

space-time structure of heavy ions collisions

kinetic freeze-out(no collisions)

Chemical freeze-out(no particles production)

Parton-parton interaction

Initial inelastic collisions

88

RRelativistic elativistic HHeavy eavy IIon on CCollider (ollider (RHICRHIC))

99

2 rings, 3.8 km circumference.2 rings, 3.8 km circumference.Polarized p and Nucleus up to Au.Polarized p and Nucleus up to Au.

Top energies (each beam):Top energies (each beam):100 GeV/nucleon Au-Au. 250 GeV polarized p-p.100 GeV/nucleon Au-Au. 250 GeV polarized p-p.

NIM, v.499, p. 235-880, (2003)

GeV200SNN

The PHENIX Detector Детектор PHENIX регистрирует различные частицы после столкновения:фотоны, электроны, мюоны и адроны (пионы и протоны).

The PHOBOS Detector

137000 Silicon Pad Channels

1m

12m Be Beampipe

Spectrometer

Octagon

Vertex

Ring Counters

Paddle Trigger Counter

Cerenkov Counter

DX magnet DX MagnetZDC ZDC

PHOBOS

The BRAHMS Experiment95°

30°

30°

15°

2.3°

1515

Rapidity

Lorens boost

) (

) (

z

zz

pEE

Epp

zp -

ln 21

E

pEy z

0zz

y y -1 1

ln 21

p -

ln 21

p -

ln 21

EpE

EpE

y zz

Pseudorapidity

2)/ln(21

- )cos-p(1)cos1(

ln 21

pcos -

cosln

21

tgp

EpE

y

Transverse mass 22TT pmm

)(

)(

yshmp

ychmE

TL

T

1616

questions have to be answered

1.Can we achieve high energy density in nuclei-nuclei collisions ?

2.What is the barion density of prodused hadronic matter?

3.Is established thermodynamic equilibrium ?

Connected question

Can we make conclusion about from experiment?

17

STAR EVENTS

http://www.star.bnl.gov/

p+p (200 GeV) CentralAu+Au(200 GeV)

18

∫b

geo bbdbb0

2π=π2=σ )()(

Centrality classification

Value of impact parameter

Geometrical cross section

8%)(2 fm 42 b

In percent from the geometrical cross section

% 50 40Centrality

fm 9.5 (15)fm 0.63 )2( 4.0min Rb

fm 10.6 (15)fm 0.71 )2( 5.0max Rb

2)2/()2(/)( RbRb geogeo

Number of participant partN

1919

QUESTION I(a)QUESTION I(a)

How much energy lost the primary hadrons?What is barion density of prodused

hadronic matter?

Can we make some conclusion from experiment?

20

Stopping power

Net protons distribution

1.6; 5 == bNN YGeVSAGS

2.9; 17 == bNN YGeVSSPS5.4; 100 == bNN YGeVSRHIC

BRAHMS collaboration PRL 93, 1020301 (2004),

;0.0025

;0.0012

;0.17

O

O

O

=

=

=

RHIC

SPS

AGS

)proton-(-)proton()proton-( antiNNnetN =

21

(73 ± 6) GeV / nucleon(73 ± 6) %

Stopping power

BRAHMS collaboration PRL 93, 1020301 (2004),

; %673/EE

; %80/EE

%;55/EE

kk

kk

kk

±=

=

=

RHIC

SPS

AGS

2222

QUESTION I(b)QUESTION I(b)

Can we have high energy densityin nuclei-nuclei collisions ?


2323

Energy density and Bjorken equation

><=

τ=τβπ== 2

T

FF

mNE

ySRSV

)(

TF

mdy

dN

SV

E

1

εBj

J.D. Bjorken, Phys. Rev. D27 (1983) 140.

24

Dependence on centrality of charged hadron density

S.S. Adler et al. , Phys. Rev. C 71, 034908 (2005)

>η<>η>=<< ddNddEm chTT ///

Dependence on pseudorapidity of charged hadron

Do not confuse it is the other distribution

B. Alver et al.Phys. Rev. C 83, 024913 (2011) PHOBOS Coll.

)proton-(-)proton()proton-( antiNNnetN =

26


The CMS collaboration, J.High Energy Phys 08, p.141 (2011)

27


The CMS collaboration, J.High Energy Phys 08, p.141 (2011)

«LHC multiplicity is two times greater than at RHIC»

28

Dependence on centralty of charged hadron


>η<>η>=<< ddNddEm chTT ///

29


2

2

2

2

2

2

GeV/fm 3.11TeV; 2.76

GeV/fm 0.6)5.4(GeV; 200

GeV/fm 0.5)4.7(GeV; 130

GeV/fm 0.2)2.2(GeV; 19.6

GeV/fm 2.9GeV; 17

GeV/fm 1.5GeV; 5

FBjNN

FBjNN

FBjNN

FBjNN

FBjNN

FBjNN

S

S

S

S

S

S

30

dydE

SSdy

mdNT

Form

TFormBj

..

1)(

Historically, the energy density is estimated using

cfmForm /. 1

3./ 5.1; 5;: fmGeVBjGeVSAuAuAGS NN 3./ 9.2; 17;: fmGeVBjGeVSPbPbSPS NN

3./ 4.5; 200 ;: fmGeVBjGeVSAuAuRHIC NN

Energy density and Bjorken equation

3./ 3.11; 76.2 ;: fmGeVBjTeVSPbPbLHC NN

3131

Energy density and crossing time

crossing time

130 2 fm/c.γ/R RHIC - 61 2 fm/c.γ/RSPS - /3.5 /2 - cfmRAGS

Energy density is determined from final state parametersEnergy density is determined from final state parameters

For TF m/ and GeV 6.0 Tm / 0.35 cfmF

RHIC / 15 3fmGeVBj

init.final BjBj

Fτbe to have <γ2 /R≈

LHC / 30 3fmGeVBj

3232

Can we achieve high energy densityin nuclei-nuclei collisions ?


Yes! For RHIC and LHC energy

QUESTION I(b)QUESTION I(b)

LHC

RHIC

Bj

Bj

;GeV/fm GeV/fm

;GeV/fm GeV/fm 33

33

1>>30ε

1>>15ε

≥

≥

3333

QUESTION IIQUESTION II

Is equilibrium state of hot and dense hadronic matter achieved?

What is conclusions from experiment?

3434



The possible observableParticle ratios Particle spectra Collective flows

… ?

3535

Particle ratio and sParticle ratio and statistical modelstatistical models

These models reproduce the ratios of particle yields with only two (or three ) parameters

One assumes that particles are produced by a thermalized system with temperature T and baryon chemical potential

The number of particles of mass m per unit volume is :

3636

Particle ratios and statistical model(s)

Peter Braun-Munzinger, Krzysztof Redlich, Johanna StachelarXiv:nucl-th/0304013v1, (2003)«Of particular interest is the extent to which the measured particle yields are showing equilibration.»

A. Tawfik ; arXiv:hep-ph/0508244v3 22 Mar 2006

Statistical methods have become an important tool to study the propertiesof the fireball created in high energy heavy ion collisions, where theysucceed admirably in reproducing measured yield ratios.1. Can this success be taken as evidence that the matter produced in these

collisions has reached thermal and chemical equilibrium?2. Can the temperature and chemical potential values extracted from such

statistical model fits be interpreted as the equilibrium properties of the collision matter?

STAR Coll., Nucl. Phys. A 757 (2005) 102

3838

Particle ratiosParticle ratios

S. S. Adler, et al., Phys. Rev. C69 (2004) 034909

3939

Particle ratios and sParticle ratios and statistical modelstatistical models

chemical freez-out

Nucl. Phys. A758, No.1-2, p.184, (2005)

4040


4141


42

arXiv:nucl-th/0304013 v1 3 Apr 2003

Peter Braun-Munzinger, Krzysztof Redlichb, Johanna Stachel

Low energy (NA49)

Katarzyna Grebieszkow for the NA49 and the NA61 CollaborationsACTA PHYSICA POLONICA Vol. B41, No 2,p.427 (2010)

4444

Particle (hadrons) Particle (hadrons) spectraspectra

kinetic freeze-out

4545


R. Stock; «Quark Matter 99 Summary: Hadronic Signals»arXiv:hep-ph/9911408v1 19 Nov 1999

46

T. Csorgo and B. Lorstad, Phys. Rev. C 54, 1390 (1996)

BorisTomasic, arXiv:nucl-th/0304079 v1 25 Apr 2003

blast-wave model

1. Pions, nucleons and also kaons decouple all quite suddenly from the whole transverse profile of the fireball. For all of them the freeze-out happens at the same proper time, measured in a frame that co-moves longitudinally with the fluid element of the expanding firebal

2. The radial density distribution at the freeze-out is uniform.3. Longitudinal expansion is boost-invariant. 4. In this study, the transverse expansion is parametrized through

rapidity, which depends linearly on the radial coordinate.

47

BorisTomasic, arXiv:nucl-th/0304079 v1 25 Apr 2003

4848


A Iordanova (for the STAR Collaboration);J. Phys. G35, p.044008, (2008

4949

elliptic flowelliptic flow

Coordinate space asymmetry momentum space anisotropy

22x

22x

2 y

y

pp

ppv

Space eccentricityElliptic flow

22

22

yy

xx

Directed flow

5050

Elliptic flowElliptic flow

For big value of elliptic flow you need save space anisotropy for a long enough timeThe value of elliptic flow is sensitive to the Equation of State (EoS)

Importance of elliptic flowImportance of elliptic flow

1.Give information about equilibration time2.Give information about EoS

On the next slides shown how ensemble of free streaming particles lost space eccentricity

5151

TIME = 0 fm/c, 0.7

5252

TIME = 1 fm/c, 0.6

5353

TIME = 2 fm/c, 0.5

5454

TIME = 3 fm/c, 0.3

:

elliptic flow hydrodynamicselliptic flow hydrodynamics

elliptic flow and space eccentricityelliptic flow and space eccentricity

ε/=A 2v 2

Evidence for the short thermailzation time

Good description of elliptic flow by hydrodynamics with initiation conditionjust from geometry of collision

Constant ratio of elliptic lowto the space eccentricity

Fast decreasing of space anisotropy for the free streaming particle



What is the conclusion about it from experiment?

The strong indication that YES.

/ 1 cfmTherm

Some designations

sQGP for strongly-interacting Quark-Gluon Plasma

Commonly accepted:QGP, pQGP,wQGP

for weakly-interacting Quark-Gluon Plasma

Observables and hadronic matter properties

60

KEKETT – CQN Scaling – CQN ScalingKEKETT – CQN Scaling – CQN Scaling

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

Mesons

Baryons

Quark-Like Degrees of Freedom EvidentQuark-Like Degrees of Freedom EvidentAs well as an Indication for strong coupling?As well as an Indication for strong coupling?

Roy A. Lacey, Stony Brook; Quark Matter 09, Knoxville, TN March 30 -

April 4, 2009

61

K. Aamodt et al.(ALICE Collaboration), PRL 105, 252302 (2010)

elliptic flow – energy elliptic flow – energy dependancedependance

6262

JET Quenching

Modification of Jet property in AA collisions because partons propagating in colored matter lose energy.

One of the possible observableTp

Was predicted in a lot of works. Some of them (not all) are:

1

0)(Pd

J.D.Bjorken (1982), Fermilab – PUB – 82 – 059 - THY.M.Gyulassy and M.Palmer, Phys.Lett.,B243,432,1990.X.-N.Wang, M.Gyulassy and M.Palmer, Phys.Rev.,D51,3436,1995.R.Baier et al., Phys.Lett.,B243,432,1997.R.Baier et al., Nucl.Phys.,A661,205,1999

The suppression of the high- hadrons In AA collisions

Jet: A localized collection of

hadrons which come from a fragmenting parton

High pT (> ~2.0 GeV/c) hadrons in NN

h

h

h

abc

dParton distribution functions

Hard-scattering cross-section

Fragmentation Function

h

)Q,x(f 2aaa/A )Q,x(f 2

bbb/B cdabd )Q,z(D 2ddd/h

d,c,b,ahXABd

h

High pT (> ~2.0 GeV/c) hadrons in AA

A

B

h Hard-scattering cross-section

Fragmentation Function

Parton distribution functions

+Numbers of binary collisionsPartonic Energy

Loss

(...)f b/B(...)f a/A cdabd

)Q,z(D 2d

*dd/h

1

0 d

*d

z

z)(Pd

∑→dcba

hXABd,,,

=σ CollN

6565

Nuclear modification factor

is what we get divided by what we expect.is what we get divided by what we expect.

NN

collAAAA d

NdR

σ><σ

=/

From naive picture

AAR

Suppression of high-pt hadrons. Qualitatively.

6666

First data in first RHIC RUN

Jet Quenching ! Great!

But (see the next slide)

6767

Nuclear modifications to hard scattering

Large Cronineffect at SPSand ISRSuppression at RHIC

Is the suppression due to the medium?(initial or final state effect?)

RAA ( pT )d2N AA /dpT d

TAA d2 NN /dpT d

6868

Au+Au @ sNN

= 200 GeV d+Au @ sNN

= 200 GeV

preliminary

Au+Au @ sNN


= 200 GeV

preliminary

Au+Au @ sNN


= 200 GeV

preliminary

Au+Au @ sNN


= 200 GeV

preliminary

• Nice picture! Isn’t it?

Again Au+Au and d+Au

6969

The matter is so opaque that even The matter is so opaque that even

a 20 GeV a 20 GeV 00 is stopped is stopped..

• Suppression is very strong (RAA=0.2!) and flat up to 20 GeV/c• Common suppression for 0 and it is at partonic level• > 15 GeV/fm3; dNg/dy > 1100

70

.ALICE Collaboration, Physics Letters B 696 (2011) 30.

71

ALICE Collaboration, Physics Letters B 696 (2011) 30

7272

The matter is so dense that even heavy quarks are stopped

Even heavy quark (charm) suffers substantial energy loss in the matter

The data provides a strong constraint on the energy loss models.

The data suggest large c-quark-medium cross section; evidence for strongly coupled QGP?(3) q_hat = 14 GeV2/fm

(2) q_hat = 4 GeV2/fm


(4) dNg / dy = 1000

7373

If there are any other observables for Jet Quenching?

Correlation of trigger particles 4<pT<6.5 GeV withassociated particles 2<pT<pT,trig

Associated particles

Near side jetTrigger particle

Away side jet

Yes! Back to Back Jets correlation.

7474

In-plane In-plane

Out-of-plane

Out-of-plane

Back to Back Jets correlation.Back to Back Jets correlation.Dependence from reaction plane.Dependence from reaction plane.

7575

Jet tomography

20-60%

STAR Preliminry

20-60%

Back-to-back suppression depends on the reaction plane orientation

In-plane

Out-plane

energy loss dependence energy loss dependence on the path length!on the path length!

7676

The matter is so dense that it The matter is so dense that it modifies the shape of jetsmodifies the shape of jets

• The shapes of jets are modified by the matter.– Mach cone?– Cerenkov?

• Can the properties of the matter be measured from the shape?– Sound velocity– Di-electric

constant• Di-jet tomography is

a powerful tool to probe the matter

7777

Resonances melting (Debye scrinig)

7878

One more results from lattice QCD

heavy-quark screening mass

r/)rexp(~)r(

In EM plasma it is well known Debye screening

T/1~r/1 D

/J -- suppression

7979

The matter is so dense that it melts(?) J/ (and regenerates it ?)

CuCu

200 GeV/c

AuAu

200 GeV/c

dAu

200 GeV/c

AuAuee

200 GeV/c

CuCuee

200 GeV/c

J/’s are clearly suppressed beyond the cold nuclear matter effect

The preliminary data are consistent with the predicted suppression + re-generation at the energy density of RHIC collisions.

Can be tested by v2(J/)?

The matter is so dense that it melts Y.

QM’11 140±110±560=600 ...%)-(AAR

070±170±340=100 ...%)-(AAR

GeV .)S(Υ

GeV )S(Υ

GeV .)S(Υ

4103

102

59≈1

≈

≈

direct photons

8181

• T0max ~ 500-600 MeV !?

T0ave ~ 300-400 MeV !?

8282

SummarySummary

o RHIC has produced a strongly interacting,RHIC has produced a strongly interacting, partonic state of dense matterpartonic state of dense matter

/ 15 3fmGeVBj

8383

SummarySummary

o The matter is so dense that even heavy quarks are stopped




(4) dNg / dy = 1000

8484

SummarySummary

o The matter is so strongly coupled that even heavy quarks flow

8585

SummarySummary

o The matter is so dense that it melts(?) J/ (and regenerates it ?)

8686

SummarySummary

o The matter modifies jets

8787

SummarySummary

8888

The matter may melt but regenerate J/’s

Put the results together

The matter is denseThe matter is strongly coupled

The matter is hot

The matter modifies jets

> 15 GeV/fm3

dNg/dy > 1100

Tave = 300 - 400 MeV (?)PHENIX preliminary

8989

Backup slidesBackup slides

Miklos Gyulassy and Larry McLerran arXiv:nucl-th/0405013 v2 19 Oct 2004

January 6, 2002 RHIC/INT Winter Workshop 2002 91

Modeling the Source• Interaction region

Assembly of classical boson emitting sources in space-time region

• The source S(x,p) is the probability boson with p is emitted from xDetermines single-particle momentum spectrum

E d3N/dp3 = d4x S(x,p)

Determines the HBT two-particle correlation function C(K,q) C(K,q) ~ 1 + | d4x S(x,K) exp(iq·x) | 2/| d4x S(x,K) |2

where K = ½(p1 + p2) = (KT, KL), q = p1 – p2

The LCMS frame is used (KL = 0)

• In the hydrodynamics-based parameterizations: assume something about the source S(x,p)Gaussian particle density distribution

Linear flow (rapidity or velocity) profile

Instantaneous freeze-out at constant proper time (“sharp”)

CollN(...)/ aAf (...)/ bBf cdabd

1

0 d

*d

z

z)(Pd )Q,z(D 2

d*dd/h∑

dcba ,,,

(...)/ aAf (...)/ bBf cdabd ),(/2dddh QzD∑

dcba ,,,

9696

Why the collisons of heavy nuclei is interesting?

Let us see on the space – time picture of collision

pre-collision QGP (?) and parton production

hadron production

hadron reinteraction

QCD phase diagram

9797

The QGP in the early universe

9898

What kind of transition is predicted by lattice QCD

99



100100

• The first promising result of direct photon measurement at low pT from low-mass electron pair analysis.

• Are these thermal photons? The rate is above pQCD calculation. The method can be used in p+p collisions.

• If it is due to thermal radiation, the data can provide the first direct measurement of the initial temperature of the matter.

• T0max ~ 500-600 MeV !?

T0ave ~ 300-400 MeV !?

The matter is so hot that it emits (thermal?) photon copiously

101101

Theoretical explanation

Comparison to model calculations with and without parton energy loss:

Numerical values range from ~ 0.1 GeV / fm (Bjorken, elastic scattering of partons)~several GeV / fm (BDMPS, non-linear interactions of gluons)

Too many approaches.We need additional data!

2.0~Rand,p~d AuAu8

T

2.0~p/p

Estimation from data

102102

Initial state effects (test experiment d+Au)

Suppression in central Au+Au due to final-state effects

/h

103103

Binary scaling. Is it work?

104104

How about suppression for protons?

pcollccollCP )N/dN/()N/dN(R New

Close to nuclear mod. factor, because no suppression for peripheral coll.

105105

Jets composition as measured by STAR

Kirill Filimonov, QM’04

106106

107107

[w/ the real suppression]

( pQCD x Ncoll) / background Vogelsang/CTEQ6

[if there were no suppression]

( pQCD x Ncoll) / ( background x Ncoll)

Au+Au 200 GeV/A: 10% most central collisions

[]measured / []background = measured/background

Preliminary

pT (GeV/c)

Binary scaling. Is it work?

108108

Theoretical explanation

Comparison to model calculations with and without parton energy loss:

Numerical values range from ~ 0.1 GeV / fm (Bjorken, elastic scattering of partons)~several GeV / fm (BDMPS, non-linear interactions of gluons)

Too many approaches.We need additional data!

109109

If is there space for Color Glass Condensate or only Cronin Effect?

May be. Look at the BRAMS DATA

110110

111111

Observables and space time structureObservables and space time structure of of Heavy ion collisionsHeavy ion collisions

112112


Production of hard particles: jets heavy quarks direct photonsCalculable with the tools of perturbative QCD

113113


Production of semi-hard particles: gluons, light quarks relatively small momentum: make up for most of the multilplicity

cGeVpT / 21

114114


Thermalizationexperiment suggest a fast thermalization (remember elliptic flow)but this is still not undestood from QCD

115115


Quark gluon plasma

116116


Hot hadron gas

117117

Particle ratio and sParticle ratio and statistical modelstatistical models

These models reproduce the ratios of particle yields with only two parameters

One assumes that particles are produced by a thermalized system with temperature T and baryon chemical potential

The number of particles of mass m per unit volume is :

118118

N/ ratio shows baryons enhanced for pT < 5 GeV/c

One more observable. Particle ratios

Heavy Ions Collisions (results and questions)

Documents

Transcript of Heavy Ions Collisions (results and questions)