heavy ions collisions (results and questions)

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

Anatoly LitvinenkoElena Litvinenko

[email protected]@nf.jinr.ru

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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

66

Lattice QCD

GeVTc 0.17=

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

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

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space-time structure of heavy ions collisions

kinetic freeze-out(no collisions)

Chemical freeze-out(no particles production)

Parton-parton interaction

Initial inelastic collisions

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

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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°

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?

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STAR EVENTS

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

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

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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?

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Stopping power

Net protons distribution

BRAHMS collaboration PRL 93, 1020301 (2004),

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Stopping power

BRAHMS collaboration PRL 93, 1020301 (2004),

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QUESTION I(b)QUESTION I(b)

Can we have high energy densityin nuclei-nuclei collisions ?


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Energy density and Bjorken equation

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Dependence on centrality of charged hadron density

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

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.

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

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

«LHC multiplicity is two times greater than at RHIC»

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Dependence on centralty of charged hadron


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Can we have high energy densityin nuclei-nuclei collisions ?


Yes! For RHIC and LHC energy

QUESTION I(b)QUESTION I(b)

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QUESTION IIQUESTION II

Is equilibrium state of hot and dense hadronic matter achieved?

What is conclusions from experiment?

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The possible observableParticle ratios Particle spectra Collective flows

… ?

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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 :

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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.»

Estimation of equlibration time for RHIC and LHC (have to be studied)R. Baier, A.H. Mueller, D. Schiff, and D.T. Son, Phys. Lett. B 502 (2001)51; Nucl. Phys. A698 (2002) 217.

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

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Particle ratiosParticle ratios

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

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Particle ratios and sParticle ratios and statistical modelstatistical models

chemical freez-out

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

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4141


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arXiv:nucl-th/0304013 v1 3 Apr 2003

Peter Braun-Munzinger, Krzysztof Redlichb, Johanna Stachel

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Particle (hadrons) Particle (hadrons) spectraspectra

kinetic freeze-out

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

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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.

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

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

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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

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TIME = 0 fm/c, 0.7

5151

TIME = 1 fm/c, 0.6

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TIME = 2 fm/c, 0.5

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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.

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

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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 Evident

Roy A. Lacey, Stony Brook; Quark Matter 09, Knoxville, TN March 30 - April 4, 2009

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

elliptic flow – energy elliptic flow – energy dependancedependance

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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

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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.

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First data in first RHIC RUN

Jet Quenching ! Great!

But (see the next slide)

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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 /dpTdTAAd

2 NN /dpTd

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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

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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

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

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ALICE Collaboration, Physics Letters B 696 (2011) 30

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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

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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.

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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.

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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!

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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

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Resonances melting (Debye scrinig)

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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

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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

direct photons

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• T0max ~ 500-600 MeV !?

T0ave ~ 300-400 MeV !?

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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

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SummarySummary

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




(4) dNg / dy = 1000

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SummarySummary

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

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SummarySummary

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

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SummarySummary

o The matter modifies jets

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SummarySummary

The matter is hot 8787

The matter may melt but regenerate J/’s

Put the results together

The matter is denseThe matter is strongly coupled

The matter modifies jets

> 15 GeV/fm3

dNg/dy > 1100

Tave = 300 - 400 MeV (?)PHENIX preliminary

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Backup slidesBackup slides

January 6, 2002 RHIC/INT Winter Workshop 2002 89

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 ,,,

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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

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The QGP in the early universe

9595

What kind of transition is predicted by lattice QCD

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9797

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

9898

Initial state effects (test experiment d+Au)

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

/h

9999

Binary scaling. Is it work?

100100

How about suppression for protons?

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

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

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Jets composition as measured by STAR

Kirill Filimonov, QM’04

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103103

[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?

104104

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!

105105

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

May be. Look at the BRAMS DATA

106106

107107

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

108108


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

109109


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

cGeVpT / 21

110110


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

111111


Quark gluon plasma

112112


Hot hadron gas

113113

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 :

114114

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

One more observable. Particle ratios

heavy ions collisions (results and questions)

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