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QFTHEP2010 14.09.2010

Dense strongly interacting matter: Lessons from RHIC and expectations for LHC
A. Leonidov
P.N. Lebedev Physical Institute


Main results at RHIC Multiplicities much lower than pre-RHIC predictions indicating strong coherence in particle production mechanisms. Observed elliptic flow is in agreement with hydrodynamics of (almost) ideal liquid indicating creation of dense strongly coupled matter New structures in the near-side (ridge) and away-side (Cherenkov/Mach cones) angular correlations Significant reduction in the yield of particles with large transverse momentum (jet quenching)


t
freeze out hadrons in eq. hydrodynamics gluons & quarks in eq. gluons & quarks out of eq. strong fields kinetic theory classical EOMs

z

(beam axis)


Basis of coherence in particle production: growth of gluon density at small Bjorken x at fixed Q 2 :

xP(x)

0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 10

c)

H1PDF 2009 2 2 Q = 10 GeV

xuv

xg

/20

xdv xS
/20

-4

10

-3

10
k P
+ +

-2

10

-1

x

x=


"Phase diagram" in the x - Q 2 plane:

x=

k P

+ +

S

1 Q2


Immediately after collisions there form longitudinal chromoelectric and chromomagnetic fields - glasma :

. .. .. . .. . . .
E B
z z

. .

..

..

. .. . .. . . .

= =

ig Ai(1) , Ai(2) ig
ij

Ai(1) , Aj(2)


Temporal evolution of longitudinal and transverse fields:

0.8
[(g µ) /g ]
2

Bz Ez

2

2 2

0.6 0.4 0.2 0 0 0.5 1 g µ
2

BT ET

4

2

2

1.5

2


Initial multiplicity and energy density

dN | d dE | d

=0

=c

N

22 RA QS s 2 RA Q s 3 S

=0

= cE

2 HERA QS

1.2 GeV

dN | d

=0

1100


Instabilities of the boost-invariant solution Rapidity-dependent configurations generate explisively growing transverse fields |E |, |B | e Qs New mechanism of energy losses Turbulent isotropisation? Quantum corrections to the glasma picture: GLV - BK - JIMWLK equations


Glauber geometry

Projectile B

Target A

s- b b s z

B s- b s b A

a) Side View

b) Beam-line View


Classification in centrality


Scaling in N

part

Nch / Npart/2

30

200 GeV

130 GeV

20
62.4 GeV

10
p(p)+p

19.6 GeV

0

0

200

400
Npart


Elliptic flow


Elliptic flow: some definitions
· Directed and elliptic flow v1 and v2 N dN [1 + 2v1 cos ( - ) + 2v2 cos (2( - )) + · · ·] =2 dp dyd ( - ) dp dy
2

: a reaction plane angle · Spatial anisotropy
x x

and elliptic flow
2 2

=

y2 - x y2 + x
p

;

v2

x

1 dN Soverlap dy

y =0

· Momentum anisotropy
x

=

Txx - Tyy ; Txx + Tyy

v2

p

/2


Elliptic flow: experimental data


Elliptic flow: experimental data


Elliptic flow: theory

Measured elliptic flow at small transverse momenta agrees with predictions of hydrodynamics of almost ideal (low viscosity) liquid Quantitative description requires full three-dimensional viscous hydro taking into account fluctuations of initial conditions Exciting theoretical developments: physics of sQGP as conformal relativistic hydrodynamics, etc. Exciting perspectives for theoretical development: turbulence in sQGP


Two-particle correlations: Ridge


Two-particle correlations: Ridge

Experimental situation is not very clear Theoretical explanations are not precise and not convicing


Experimental data on two-particle azimuthal correlations
1/Ntrig dN/d
2.5 < p < 3.0 GeV/c T assoc 0.5 < p < 1.0 GeV/c
T trig

3.0 < p

trig T

< 4.0 GeV/c

4.0 < p

trig T

< 6.0 GeV/c

6.0 < p

trig T

< 10.0 GeV/c

1

1

1

1

0.5

0.5

0.5

0.5

0
1.0 < p
assoc T

0
< 1.5 GeV/c Au+Au 0-12% Au+Au || < 0.7 d+Au

0

0

0.4

0.4

0.4

0.4

0.2

0.2

0.2

0.2

0
1.5 < p
assoc T

0
< 2.5 GeV/c

0

0

0.4

0.4

0.4

0.4

0.2

0.2

0.2

0.2

0
2.5 < p
assoc T

0
< 4.0 GeV/c

0

0

0.2

0.2

0.2

0.2

0.1

0.1

0.1

0.1

0 -1 0 1 2 3 4

0
5-1

0 0 1 2 3 4 5-1 0 1 2 3 4

0 5-1 0 1 2 3 4



5


Theory of two-particle azimuthal correlations

Two possible explanations: Cherenkov gluons and Mach cones Description in terms of Cherenkov gluons possible. Its validity depends on the validity of quasiparticle approach to sQGP. Description in terms of Mach cones possible for special initial conditions. Difficult to get transverse momentum dependence of the away-side structure.


Jet quenching

h RAB

(p , y | centrality) =

dN AB dp dy

h

N

AB coll

(centrality )

dN pph dp dy


E*d /dp (mbGeV-2c3)

E*d /dp (mbGeV -2c3)

102 10 1 10-1 10 10
-2 -3

102 10 1
-1



0

(++- )/2

3 3

10

3

10 10 10 10

-2

3

-3

-4

10-4 10 10
-5 -6

-5

0 0.5

1 1.5

2 2.5

3 3.5

4 4.5

p

T

(GeV/c)

10-7 10 10
-8 -9

NLO pQCD (by W.Vogelsang) CTEQ6M PDF; KKP FF µ= p /2, p , 2p
T T T

(Data-pQCD)/pQCD

0
1 0.5 0 -0.5 0

2

4

6

8 10 12 14 16 18 20 9.7% normalization uncertainty
is not included

2

4

6

8

10

12

14

16

18

20

pT (GeV/c)


E d /dp3 (mb GeV-2 c 3 )

10 1 10 10 10 10 10 10 10
-1

-2 -3 -4 -5 -6 -7

3

pQCD µ = pT MRST2002 PDF; fDSS FF NLL NLO

a)
b)
NLO 2

0

4

6

8

4

(Data-QCD)/QCD

2 0 4 2 0
0 2 4 6

c)

NLL

p

8

T (GeV/c)


AA

R

1.5

PHENIX preliminary Au+Au 200GeV 0-10 %

0 h++h-/2

1

0.5

0 0

5

10

15

pT(GeV/c)

20


AA

R

Vitev, sNN = 22.4 GeV, no energy loss

2

sNN = sNN = sNN = Vitev, Vitev, Vitev,

22.4 GeV 62.4 GeV 200 GeV g 22.4 GeV, 130 < dN /dy < 185 g 62.4 GeV, 175 < dN /dy < 255 g 200 GeV, 255 < dN /dy < 370

1.5

Cu+Cu, 0-10% most central

1

0.5

0

0

5

10

pT (GeV/c)

15



Jet quenching: theory

Quenching of heavy quarks not understood Charmonium quenching not understood Models with calculation energy loss still not too realistic Expected progress: accurate treatment of coherence length Expected progress: Energy loss in ADS/CFT. Drastic prediction: limiting value for the energy loss.


In-medium QCD cascade


In-medium QCD cascade: models
· Two types of QCD cascades: · Cascade driven by degradation of virtuality (DGLAP) · Cascade driven by medium-induced particle production (similar to electromagnetic showers in matter) · Rigorous description combining both effects is currently not available. Medium effects are taken into account by phenomenological "deformations" of one of the two basic alternatives · Most studies "deform" the DGLAP evolution.


EXPERIMENTAL RESULTS ON JET STRUCTURE AT RHIC Ratio of fragmentation functions in AA and pp collisions

STAR preliminary AR preliminary ST stat. errors only stat. errors only

p

t,jetrec.(pp)>30

GeV GeV

p

t,jetrec.(pp)>30


Current conclusions on the experimental situation:
· Observed fragmentation functions in AA collisions are the same as in pp ones. · Natural explanation: jet finding procedures bias the ensemble in such a way that only jets coming from the surface of the hot fireball are detected. · Prospects of improving the situation unclear.


Predictions for
LHC: multiplicity
ch =0 Wolschin et al. Sarkisyan et al. Sa et al. Porteboeuf et al. Mitrovski et al. Lokhtin et al. Kharzeev et al. Jeon et al. Humanic. Fujii et al. Eskola et al. El et al. Dias de Deus et al. Chen et al. Capella et al. Chaudhuri Bzdak Busza Bopp et al. Topor Pop et al. Armesto et al. Armesto et al. Arleo et al. Albacete Abreu et al.

dN /d|

in PbPb at sNN=5.5 TeV for Npart=350
corr., RDM CQM + Landau hydro corr., PACIAE EPOS corr., UrQMD corr., HYDJET++ saturation data driven, limiting frag. corr., NN superposition fcBK evolution corr., EKS98+geom. sat. corr., BAMPS percolation corr., AMPT+gluon shad. DPM+Gribov shad. log. extrap. corr., wounded diq. mod. data driven, limiting frag. corr., DPMJET III corr., HIJING/BB v2.0 PSM geom. scaling corr., log. extrap. corr., rcBK evolution corr., logistic evol. eq.

25

20

15

10

5

0

0

1000

2000

3000

4000

5000

6000


Predictions for LHC : R
R
16
PbPb(pT=20,50

AA

GeV,=0) in central Pb+Pb at sNN=5.5 TeV
Zakharov, 0, 5 % (T0 =404 MeV=1.26T
RHIC 0

), rad.+coll.+1d exp., shad.

14 12 10 8 6 4 2 00 0.2 0.4

Wang et al., 0 , 5 % (0~3.3RHIC), WW eloss+1d exp., shadowing 0 Vitev, 0, 10 %, GLV+g-feedb.+cold eloss, dN /dy~1.7-3.3(dN /dy) Pantuev, charged, N
part g g RHIC

=350,

form QGP

=1.2 fm~0.5(

form RHIC QGP)

Lokhtin et al., charged, 10 % (dN /d~2700), rad.+coll. eloss in MC Kopeliovich et al., , 10 %, early hadronization
0

ch

Liu et al., + , p

highest T T

=40, 10 %, 2<->2 w. conv., transv. exp.
RHIC =40, 10 % ( =1 fm), BH eloss+QW, E=( E) EE g g RHIC

Jeon et al., 0 , p
0

highest

Wicks et al., , 10 %, rad.+coll. eloss, dN /dy~1.75-2.9(dN /dy)
ch s

Qin et al., charged, 10 % (dN /d~2500), AMY+hydro, =0.25-0.33 Renk et al., 0, 10 % (dN /d~2500), BDMPS QW with hydro evol. Dainese et al., 0, 10 %, BDMPS QW with WS, q~2-7q
0 ch RHIC ch

Cunqueiro et al., , 10 % (dN /d~1500), percolation Capella et al., 0 , 10 % (dN /d~1800), comovers, kinematics Arleo et al., charged, 10 % (dN /d ~1300), =50 GeV
c ch ch

0.6

0.8

1

1.2

1.4


Predictions for LHC : conservative expectations

Coherence effects in multiparticle production stronger than at RHIC Elliptic flow less or similar than at RHIC Jet quenching similar at intermediate transverse momenta, weaker at large In general: more intense and longer living sQGP, similar hadronization We'll learn some of it by the end of 2010. First heavy ion run at LHC: November 2010


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