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Some results obtained at RHIC. Anatoly Litvinenko. [email protected]. Outline. Introduction RHIC. Short introdaction Why we study nuclei-nuclei collisions? A few definitions. What can we expect from theory Properties of produced hadronic matter (observables) - PowerPoint PPT Presentation
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1
A.Litvinenko July 2008,
Some results obtained at RHICSome results obtained at RHIC
Anatoly Litvinenko
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A.Litvinenko July 2008,
Outline.Outline.
Introduction RHIC. Short introdaction Why we study nuclei-nuclei collisions?
A few definitions. What can we expect from theory Properties of produced hadronic matter (observables)
Energy density equilibration time (elliptic flow) jet qenching Resonances melting (Debye scrinig)
Conclusions
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A.Litvinenko July 2008,
RRelativistic elativistic HHeavy eavy IIon on CCollider (ollider (RHICRHIC))
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A.Litvinenko July 2008,
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
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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
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The QGP in the early universe
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What kind of transition is predicted by lattice QCD
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Rough estimation – ideal mass less gas
Bosons -- 1- degree of freedom:
423
02
4B T
301)T/exp(d
1).Fm(
8
7T
301)T/exp(d
1).Fm( 4
23
02
4F
Fermions -- 1- degree of freedom:
2 quarks
3 quarks
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Lattice QCDQualitative
GeV17.0Tc
F. Karsch, Lecture Notes in Physics 583 (2002) 209.
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42
42
3037
30}82
87
3222{ TTcscqsfSB
42
42
305.47
30}82
87
3223{ TTcscqsfSB
For
GeVTc 17.0
3/ 26.12 fmGeVN SBf 3/ 6.13 fmGeVN SBf
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Questions to be answered (experiment)
1.What is the value of energy density?2. If the statistical equilibration is achieved? 3.Observables and hadronic matter properties.
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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
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Stopping power
Net baryons distribution
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73 ± 6GeV / nucleon
Stopping power
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b2R ~ 15 fm
Centrality determination
Participant Region Spectators
Spectators
Central collision, b = 0 Peripheral collisoin, b 2R
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R
geo Rbdb2
0
2)2(2
Centrality classification
Value of impact parameter
Geometrical cross section
fm 42 b
In percent from the geometrical cross section
% 50 40 Centrality
Corresponds to the region impact parameter
fm 9.5 (15)fm 0.63 )2( 4.0min Rb
fm 10.6 (15)fm 0.71 )2( 5.0max Rb
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Spectator distribution for different centrality
ZDC – Zero Degree Calorimeter
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QUESTION IQUESTION I
Can we achieved enough energy densityin nuclei-nuclei collisions ?
Can we make some conclusion about from experiment?
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dydE
SSdy
mdNT
Form
TFormBj
..
1)(
Historically energy density was estimated using final dy
dET
cfmForm /. 13./ 5.1; 5;: fmGeVBjGeVSAuAuAGS NN 3./ 9.2; 17;: fmGeVBjGeVSPbPbSPS NN
3./ 4.5; 200 ;: fmGeVBjGeVSAuAuRHIC NN
Energy density and Bjorken equation
for
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A.Litvinenko July 2008,
Energy density but
crossing time Form.τbe to have /2 R
130 2 fm/c.γ/R RHIC - 61 2 fm/c.γ/RSPS - /3.5 /2 - cfmRAGS
Energy density is determined using final state
For TForm m/ and GeV 6.0 Tm / 0.35 cfmForm
/ 15 3fmGeVBj
init.final BjBj
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Can we achieved enough energy densityin nuclei-nuclei collisions ?
Can we make some conclusion about from experiment?
Yes! Bjorken equation
QUESTION IQUESTION I
33. GeV/fm 1GeV/fm 15)( FormBj
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QUESTION IIQUESTION II
Is equilibrium state of hot and dense hadronic matter achieved?
What is conclusions about from experiment?
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The answer is not evident.
Asymptotic freedom
High energy density Small coupling constant
Big equilibration time
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elliptic flowelliptic flow
Coordinate space asymmetry momentum space anisotropy
22x
22x
2 y
y
pp
ppv
Space eccentricity Elliptic flow
...)2cos2cos21(2
121
vv
d
dN
22
22
yy
xx
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A.Litvinenko July 2008,
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
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TIME = 1 fm/c, 0.6
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TIME = 2 fm/c, 0.5
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A.Litvinenko July 2008,
TIME = 3 fm/c, 0.3
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elliptic flow and space eccentricityelliptic flow and space eccentricity
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Sensitivity to nuclear EoSSensitivity to nuclear EoS
Science, Vol 298, Issue 5598, 1592-1596, 22 November 2002Determination of the Equation of State of Dense Matter Pawel Danielewicz, Roy Lacey, William G. Lynch
Directed Flow: Elliptic flow:
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QUESTION IIQUESTION II
Is equilibrium state of hot and dense hadronic matter achieved?
What is conclusions about from experiment?
The strong indication that YES.
/ 1 cfmTherm
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Some designations
sQGP for strongly-interacting Quark-Gluon Plasma
It is not reasons to expect strong changes in observables because the transition is crossover
Commonly accepted:
QGP, pQGP,wQGP for weakly-interacting Quark-Gluon Plasma
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Observables and space time structureObservables and space time structure of of Heavy ion collisionsHeavy ion collisions
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A.Litvinenko July 2008,
Observables and space time structureObservables and space time structure of of Heavy ion collisionsHeavy ion collisions
Production of hard particles: jets heavy quarks direct photonsCalculable with the tools of perturbative QCD
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Observables and space time structureObservables and space time structure of of Heavy ion collisionsHeavy ion collisions
Production of semi-hard particles: gluons, light quarks relatively small momentum: make up for most of the multilplicity
cGeVpT / 21
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Observables and space time structureObservables and space time structure of of Heavy ion collisionsHeavy ion collisions
Thermalizationexperiment suggest a fast thermalization (remember elliptic flow)but this is still not undestood from QCD
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Observables and space time structureObservables and space time structure of of Heavy ion collisionsHeavy ion collisions
Quark gluon plasma
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Observables and space time structureObservables and space time structure of of Heavy ion collisionsHeavy ion collisions
Hot hadron gas
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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 :
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Particle ratios and sParticle ratios and statistical modelstatistical models
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N/ ratio shows baryons enhanced for pT < 5 GeV/c
One more observable. Particle ratios
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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
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High pT (> ~2.0 GeV/c) hadrons in NN
h
h
A
abc
dParton distribution functions
Hard-scattering cross-section
Fragmentation Function
B
)Q,x(f 2aaa/A )Q,x(f 2
bbb/B cdabd )Q,z(D 2ddd/h
d,c,b,ahXABd
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High pT (> ~2.0 GeV/c) hadrons in NN
h
h
A
abc
dParton distribution functions
Hard-scattering cross-section
Fragmentation Function
B
)Q,x(f 2aaa/A )Q,x(f 2
bbb/B cdabd )Q,z(D 2ddd/h
d,c,b,ahXABd
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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
biaryAAAA d
N/dR
From naive picture
AAR
1
0 d
*d
z
z)(Pd (...)f b/B(...)f a/A
(...)f b/B(...)f a/A
)Q,z(D 2d
*dd/h
)Q,z(D 2d
*dd/h
cdabd
cdabd
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 /dpT d
TAA d2 NN /dpT d
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Au+Au @ sNN
= 200 GeV d+Au @ sNN
= 200 GeV
preliminary
Au+Au @ sNN
= 200 GeV d+Au @ sNN
= 200 GeV
preliminary
Au+Au @ sNN
= 200 GeV d+Au @ sNN
= 200 GeV
preliminary
Au+Au @ sNN
= 200 GeV d+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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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
(1) q_hat = 0 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/)?
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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
(3) q_hat = 14 GeV2/fm
(2) q_hat = 4 GeV2/fm
(1) q_hat = 0 GeV2/fm
(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
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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
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Backup slidesBackup slides
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• 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
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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
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Initial state effects (test experiment d+Au)
Suppression in central Au+Au due to final-state effects
/h
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Binary scaling. Is it work?
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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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[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?
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A.Litvinenko July 2008,
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!
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If is there space for Color Glass Condensate or only Cronin Effect?
May be. Look at the BRAMS DATA
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