Xi’an 2006 STAR 1 STAR Particle Ratios and Spectra: Energy and B dependence International...
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Transcript of Xi’an 2006 STAR 1 STAR Particle Ratios and Spectra: Energy and B dependence International...
1
Xi’an 2006
STARSTAR
STAR Particle Ratios and Spectra:
Energy and B dependence
International Workshop On Hadron Physics and Property of High Baryon Density Matter
Olga Barannikova, UIC
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Outline:
Identified measurements in STAR QCD Phase Diagram
Theoretical view Experimental probes: AGS, SPS, RHIC
Excitation functions for yields and ratios Freeze-out properties in AA collisions
Exploring the QCD phases Search for (tri)critical point
Probing Medium Hadronization mechanisms Energy Loss
Summary
Soft
Hard
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Particle Identification
Topological method
dE/dx method
K(892) + K
(1020) K + K
(1520) p + K
. . .
K0s +
+ p
+
TPC
NIM A 499, 659 (2003) NIM A 508, 181 (2003)
Kped
He3
TOF
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Transverse mass spectra
Variety of hadron species:
, p,
Au+Au, Cu+Cu, d+Au, pp
Same experimental setup!Spectral shapes: kinetic FO properties
transverse radial flow
Flavor composition: Hadro -chemistrychemical FO
propertiesTch
@ chemical FOstrangeness
production
PRL 97, 152301 (2006) nucl-ex/0601042
nucl-ex/0606014
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STARSTAR
QCD Phase DiagramLattice QCD prediction
F. Karsch, hep-lat/0401031 (2004)
TC~170 8 MeV
C~0.5 GeV/fm3
E
SC
u= d= 0, s =
The chiral phase transition changes from second to first order at a tricritical point; SC
s >>u= d 0
Presence of the strange quark shifts E to the left; CFL
Eu= d 0, s =
2nd order phase transition changes into smooth cross-over
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Theory:NJL/I Asakawa,Yazaki ’89
NJL/II ibidem
CO Barducci, et al. ’89-94
NJL/inst Berges, Rajagopal ’98
RM Halasz, et al. ’98
LSM Scavenius, et al. ’01
NJL ibidem
LR-1 Fodor, Katz ’01
CJT Hatta, Ikeda, ’02
HB Antoniou, Kapoyannis ’02
LTE Ejiri, et al. ’03
LR-2 Fodor, Katz ’04
— MIT Bag/QGP (only 1st order)
Theoretical (models and lattice) predictions for the location of the critical point.
M. Stephanov Acta Phys.Polon.B35:2939-2962,2004
Where is the Critical Point?
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Particle Yields and Statistical Models
• Thermalized system of hadrons can be described by statistical model:
Hadron species are populated according to phase space probabilities (maximum entropy) (Fermi, Hagedorn)
• Very successful in describing experimental
data T, μq, μs,V, γs,…
Mapping the Phase Diagram
Tchem
2| |
( ) /20
( , )
2 1B s
i
i i isSi i
E B TS
N g p dp
V
T
e
Schematic space–time view of a heavy ion collision
Experiment:
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Model Description of Yields
STAR white paperNuclPhysA757(05)102
T=1605 MeV
B=244MeV
s =0.990.07
2 =9.6/8 dof
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STARSTAR
B drops with collision energy
G. Roland
From calculations by Redlich et al, Becattini et al, Braun-Munzinger et al, Rafelski et al.
Baryon transport at mid-rapidity:
Smooth excitation function AGSRHIC
Similar trend for between AA and pp
Systematics of Thermal Freeze-out
Satz: Nucl.Phys. A715 (2003) 3c
filled: AAopen: elementary
Tch approaches limiting value
Can saturation trend be explained by Hagedorn hypotheses?
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Chemical Equilibrium:
s 1 s ~ u, d
T, µB,V - vary with energy,
but Λ, Ξ- yields stays constant
Change in baryon transport reflected in anti-baryons (and K)
Strangeness Production
PRL 89 (2002), 092301nucl-ex/0206008nucl-ex/0307024
H.Caines
100 200 300 400Npart
1
0.8
0.6
0.4
0.2
0
s
P. Steinberg et al..0
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Phase Diagram
1st order
QGP
Hadronic phaseCleymans and
Redlich,PRL 81(1998) 5284
Fodor, Katz JHEP04(2004)050
Freeze-out parameters approach Lattice-QCD phase boundary
~at SPS energies
FO at E 1GeV per particle
Success of Statistical Models
describing particle yieldsChemical freeze-out:
Tch , μB SIS RHIC
At RHIC (and may be SPS) chemical
freeze-out may probe the phase boundary:
Insensitive to centrality
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STARSTAR
Transverse mass spectra at mid-rapidity:
Evidence for Thermalization?
, K, p
T= 90MeV,
T=160MeV,
1/p
T d
N/d
pT
r 1tanh r (r) s f (r)and
E.Schnedermann, J. Sollfrank, U. Heinz PRC48 (1993) 2462.
T
pI
T
mKmdrr
dmm
dn TR
TT
TT
sinh
cosh
0
0
1
Blast-wave model
, K, p T = 90MeV, = 0.6 c, T = 160MeV, = 0.45 c
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Blast-Wave vs. Hydro Large flow, lots of re-interactions, thermalization likely
Tdec = 100 MeV
Kolb and Rapp,PRC 67 (2003)
044903.
Multi-strange spectra:Hydro: single Tf.o
What about fit quality?
BW: lower Tkin, higher for,K,p compared to
Tkin ~ 90 MeV, ~ 0.6
Tkin ~ Tch ~ 160 MeV
~ 0.45rescattering
at hadronization
Is Blast-Wave realistic?
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Freeze-out SystematicsT
th [G
eV
]
< r
> [c]
T. Nayak
SPSRHIC: smooth systematic behavior of all global variables Strong increase in radial flow (<mT>) from SIS to SPS
Changing trends of freeze-out parameters between AGS and SPS energies?
Back to the Future Low energy scan to find the “Landmark”
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What Points to Critical Point?TB
Endpoint~ 1, ~2, 3 Gavai, Fodor, Ejiri, Gupta Katz et al
Large fluctuations are expected when hadronization is close to Critical Point
Theory:
“Horn” structure in K+/ (smooth rise in K-/)
Hadronic models do not reproduce the “horn”
Strong increase in K/ fluctuations towards lower energies
Experiment:
7560
30200
40130
15028
22018
30012
4107.6
4706.3
5704.6
B.
7560
30200
40130
15028
22018
30012
4107.6
4706.3
5704.6
B.S
Cleymans et al.hep-ph/0511094
S
Cleymans et al.hep-ph/0511094
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Particle Spectra and Yields – major tools to study soft sector
Success of Hydro and Statistical Models
At RHIC the final system appears to be in local equilibrium
Chemical FO at RHIC (SPS?) coincides with hadronization
Energy scan at RHIC could locate Landmark of Phase Diagram
yields and ratios yields and ratios T and B
High B– Summary and Future
Soft Hydro,
Statistical Model
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High T – Probing Early Stage
High-pT particle spectra to address properties of the created medium and hadronization mechanisms in sQGP
HardpQCD,
FragmentationJet quenching
Energy loss mechanismsEnergy DensityThermalization
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High-pT Hadron Suppression
pQCD calculations of partonic energy loss
Central Au+Au:
x30 gluon density, x100 energy density
=10-20 GeV/fm3 >> C.
Hadronic models: hadronic energy loss can explain at most 20% of the effect.
~pT-independence of measured RCP unlikely that hadron absorption dominates jet quenching
Look at the ratio of the hadron spectra:
Large pT particles are suppressedin central Au+Au, but not in d+Au.
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nucl-ex/0510052Identified RAA/RCP
Particle-type dependence of Rcp at the intermediate pT Baryons exhibit less suppression
Or more enhancement??
hydro-like flow? gluon junction? coalescence/recombination?
STAR: Nucl. Phys. A 757 (2005) 102
Two groups (2<pT<6GeV/c):
, Ks, K, K*, φ mesons
p, Λ, Ξ, Ω baryons
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Baryon Enhancement
Intermediate pT:
Significant baryon/meson enhancement
Strong centrality dependence
Baryon/meson ratios become similar in AA and pp at pT~ 6 GeV/c
Fragmentation is not dominant at pT< 6 GeV/c
p+p
/K
0 s
Au+Au 0-5%
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Color-charge effects on E-Loss
Data:– No strong centrality dependence in ratios– Same suppression in Rcp above 7 GeV/c
not consistent with the jet quenching prediction (X.N. Wang, PRC 58 (2321) 19)
points to similar energy loss for partonic sources of p, pbar, and
STAR Preliminary
Energy loss in QCD matter: –Possible to test expectations of higher energy loss for gluons vs. quarks
X2 or X3 (S. Wicks et al., nucl-ex/0512076)
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Flavor-dependence of E-Loss
Light vs. Heavy Flavor : u,d c,b
Similar energy loss for partonic sources of , p and non-photonic electrons
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Particle Yields and Spectra – major tools for experimental study of QCD matter:
Mapping the Phase Diagram Observing Jet Quenching Studying Thermalization Energy Loss vs. Color-charge/Flavor
Summary and Outlook
Open Questions: Establish that jet quenching is an indicator of parton E loss (Energy
Scan would help to determine suppression turn-on, and study
systematically quark vs. gluon jets) Does the high initial gluon density inferred from parton E loss fits
demand a deconfined initial state? Location of the Critical Point (needs Energy Scan to higher B)