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High density matter (from SPS and RHIC to LHC) Carlos Pajares Universidade de Santiago de Compostela. Multiplicity Parton Saturation Elliptic Flow. sQGP, Perfect Liquid. EoS Transverse Momentum Suppression Charm, J/ Ψ suppression - PowerPoint PPT Presentation
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High density matter(from SPS and RHIC to LHC)
Carlos PajaresUniversidade de Santiago de Compostela
Multiplicity
Parton Saturation
Elliptic Flow. sQGP, Perfect Liquid. EoS
Transverse Momentum Suppression
Charm, J/Ψ suppression
Fluctuations (Multiplicity, Transverse momentum, Balance, LONG range)
Percolation of Color Sources
Color Glass Condensate
XXXV International Meeting on Fundamental Physics28 de mayo -1 de junio 2007, Santiago de Compostela
Energy density versus T/TC. Curve 1-2 quark flavours, curve 2-2 light plus oneHeavy flavour and curve 3-3 quark flavours.
MULTIPLICITY
ExtrapolationFrom lepton-Nucleon and p-A scaling on 2 2/ SQ Q
At LHC energy gives 9.5, i.e. 1800charged particles per unit rapidity
Linear energy data extrapolation gives6.5, 1200 charged particles
String percolation in between
Most of the models over 2500.
SATURATION OF PARTONS
Number of gluons. Size gluons Total Area
New Scale QS
s ( )( , )
2
2 2sS A2
s
QxG x Q R
Q
( , ) ( , , ) ( , ) 1 22 2 2
h T T dip T0Q dz d r z r Q r
* scattering h
( , ) ( , )2dip T T T Tr 2 d b N r b
*ln( / )
T T T
h
r x y
1 x y y
, parton carries emitting a new gluon
with probability
0p x P xp
ln ln
p
c s c 01ss k
1
N N xdp p
p x
ln!
n
0s
x1
n x
( , )
s s2dN
xG x Q e xd
The whole gluon cascade, (ordered in longitudinal momenta)
1p p gives
A more detailed treatment, is the BFKL eq
2 2
2 2
( )( )
2 ( ) ( )
xy T T T
s xz zy xyT T T T
N d z x yN N N
x z y z
2 2 22 2 0
0
ln ( )( ) exp
22
s
TT T
ss
r QeN r r Q
i. Grows as a power of the energy (Violation unitarity)ii. Diffusive behaviour, gluons can go inside non-perturbative region
2 2T QCDk
2 2
2 2
( )( )
2 ( ) ( )xy T T T
s xz yz xy xz zyT T T T
N d z x yN N N N N
x z y z
BK equation
Small x, interaction among gluon sources
Solution
– At lower x (higher energy) N is large but lower than 1 (solving theunitarity problem)
– At small τT, N is small (color transparency) BFKL is OK.
– The transition between small τT takes place at a characteristicvalue τT~1/QS(τ). (solving the infrared diffusion problem)
NEW SCALE QS (depends on y an A)
ELLIPTIC FLOW
Rcos( ) cos 2( - )3 3 3
1 R 23T T T T
Ed N d N d N1 2 2
dp p dp dyd 2 p dp dy
T
momentum anisotropy
pressure gradient is mainly along the direction of impact parameter (x axis)
in fluid, the p distribution will reflect the fluid profile. Spatial distribution is
2 2y x
2 2 2y x
p pV
p p
carried over
the momentum distribution. (partons or hadrons must interact each other)
eccentricity spatial anisotropy of the almond2 2y x
2 2y x
We expect
density of scatterings2
1 dnv
S dy
2v
Hydrodynamics perfect fluid result is for full thermalized system anda soft EoS
LHC?
Perfect fluid should have scaling properties
Limiting fragmentation
Centrality dependence
( ) ( )2 2 2 2y x xy
part 2 2y x
4
This scaling suggests that the collective flow is at the partonic stage
OK with coalescence models
Evidence
Perfect fluid
(interacting at partonic stage, soft EoS, low viscosity, fast thermalization)
/ behaviour2v
. for central collisions2v 0 2
scaling properties
Caveat .422
1vv 2
Transverse Momentum Suppression
Energy loss by medium induced gluonradiation
Photons in agreement with perturbative QCD
O.K. withEnergy loss dependence on Npart
Problems: Equally supressed as charged hadrons contrary to predictions (less supressed)
Non photonic electrons
Q=14 GeV2/fm
Azimuthal distribution of away-side charged hadrons
• For central collisions, suppressionof the back jet
• The widths of the back-to-backpeaks are independent of centrality (for pT (asso c)>6and 4<pT<6)
Gev/ctrigT8 p 15
Possibilities to look for supersonic jets
J/Ψ SUPPRESSION
hA
/J
WMax A
PX
P P
Data requires smaller σabs
at most 3mb (usually σabs= 4.2 mb)
No additional suppression seenat RHIC
0 mb
3 mb
Low x2 ~ 0.003(shadowing region)
σab=1mb34
Regeneration models fit the data.They predict, an increase of J/Ψ atLHC.
Lattice studies indicate no suppression of J/Ψ at T=TC, only at T≥2TC. Ψ’ and
are supressed at
Defining SJ/Ψ,Ψ’ the survival probabilities once is substracted the absorption, as
60% J/Ψ are directly produced and 40% J/Ψ come from decays of Ψ’ and
/. . obsJ XS 0 6 S 0 4 S ' Cx and
' . . 7 1 1 6 mb / ' . . J 4 3 0 3 mb
Grandchamp, Rapp, BrownPRL 92, 212301 (2004)
ThewsEur.Phys.J C43, 97 (2005)
Sequential dissociation modelcc
'c
cT T
c
The prediction for LHC isa large suppression of J/Ψcorresponding to the directlyproduced J/ Ψ.
Clear difference at LHC between regeneration and sequential models
Narrowing of the Balance function with Centrality
1B
2 N N
The width sensitive to hadronization time.Delayed hadronization narrowbalance function (stronger correlation inrapidity for the charged particles)
number of identified charged pion pairs
in ( ) ( )y y y
Caveat: In PyTHIA and other modelswith short hadronization time are able todescribe data.
The narrowing is only observed at midrapidity
00.05
0.10.15
0.20.25
0.30.35
Data CentralData Peripheral
B(y)
a)
00.05
0.10.15
0.20.25
0.30.35
0 0.5 1 1.5 2
HIJING-GEANT
B(y)
y
b)
NPTarg fluctuations contribute in target
hemisphere (most string hadronic models)
Different Extreme Reaction ScenariosMULTIPLICITY FLUCTUATIONS
NPTarg fluctuations contribute in both
hemispheres (most statistical models)
NPTarg fluctuations contribute in
Projectile hemisphere
• Multiplicity fluctuations sensitive to reaction scenario
M. Bleicher M. Gazkzicki,M. GorensteinarXiv:hep-ph/0511058
Reflection, Mixing and Transparency
• Significant amount of mixing of particles projectile and target sources
String Hadronic Models
• String hadronic models shown (UrQMD, HSD, HIJING) belong to transparency class
• They do not reproduce data on multiplicity fluctuations
Projectile hemisphere
HSD, UrQMD:V. Konchakovskyi et al.Phys. Rev. C 73 (2006)034902
HIJING:M. Gyulassy, X. N. WangComput. Phys. Commun. 83(1994) 307Simulation performed by:M. Rybczynski
PERCOLATION COLOR SOURCES
Results for the scaled variance of negatively charged particles in Pb+Pb collisions at Plab=158 AGeV/c compared to NA49 experimental data. The dashed line corresponds to our results when clustering formation is not included, the continuous line takes into account clustering.
L.Cunqueiro,E.G.Ferreiro,F del Moral,C.P.
FLUCTUATIONS AT RHIC
T
randomP
random
2 2T T
T
F
p p
p
%
• Color strings are stretched between the projectile and target
• Strings = Particle sources: particles are created via sea qq production inthe field of the string
• Color strings = Small areas in the transverse space filled with color fieldcreated by the colliding partons
• With growing energy and/or atomic number of colliding particles, thenumber of sources grows
• So the elementary color sources start to overlap, forming clusters, verymuch like disk in the 2-dimensional percolation theory
• In particular, at a certain critical density, a macroscopic cluster appears,which marks the percolation phase transition
CLUSTERING OF COLOR SOURCES
(N. Armesto et al., PRL77 (96); J.Dias de Deus et al., PLB491 (00); M. Nardi and H. Satz).
• How?: Strings fuse forming clusters. At a certain critical density ηc(central PbPb at SPS, central AgAg at RHIC, central SS at LHC ) amacroscopic cluster appears which marks the percolation phase transition(second order, non thermal).
• Hypothesis: clusters of overlapping strings are the sources ofparticle production, and central multiplicities and transverse momentumdistributions are little affected by rescattering.
LONG RANGE CORRELATIONS
• A measurement of such correlations is the backward–forward dispersion
D2FB=<nB nF> - <nB> <nF>
where nB(nF ) is the number of particles in a backward (forward) rapidity
•In a superposition of independent sources model, is proportional tothe fluctuations on the number of independent sources (It is assumedthat Forward and backward are defined in such a way that there is a rapiditywindow to eliminate short range correlations).
• Cluster formation implies a decreasing number of independent sources.Therefore DBF decreases.
2BFD
( )2ND
.1 0
• Sometimes, it is a measured
B Fn a bn
with
/2 2BF FFb D D
• b in pp increases with energy. In hA increases with A
• Clustering of strings implies a suppression of b
Color Glass Condensate
As the centrality increases, Qs increases, αs decreases an b increases
1 2
2 2sat
S
2
2 2sat2
S
S
2 4con conS sat
1 2
k y ycon
dN 1R Q
dy
dN 1R Q
dy
1 dN
dy
dN dNR Q
dy dy
dNe
dy
2S
1b
1 c
Particle production in high energy is considered as a gluon production in background classical field. The spectrum becomes thermal with
Kharzeev, Levin, Satz
/sT Q 2
/1 T
in percolation( )
2T 1
c
pT
2F
during
If you can not get rid of the noise…. study the noise
Penzias and Wilson
RHIC IIFAIRLHC
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