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

2

Xi’an 2006

STARSTAR

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

3

Xi’an 2006

STARSTAR

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

4

Xi’an 2006

STARSTAR

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

5

Xi’an 2006

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

6

Xi’an 2006

STARSTAR

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?

7

Xi’an 2006

STARSTAR

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:

8

Xi’an 2006

STARSTAR

Model Description of Yields

STAR white paperNuclPhysA757(05)102

T=1605 MeV

B=244MeV

s =0.990.07

2 =9.6/8 dof

9

Xi’an 2006

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?

10

Xi’an 2006

STARSTAR

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

11

Xi’an 2006

STARSTAR

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

12

Xi’an 2006

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

13

Xi’an 2006

STARSTAR

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?

14

Xi’an 2006

STARSTAR

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”

15

Xi’an 2006

STARSTAR

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

16

Xi’an 2006

STARSTAR

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

17

Xi’an 2006

STARSTAR

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

18

Xi’an 2006

STARSTAR

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.

19

Xi’an 2006

STARSTAR

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

20

Xi’an 2006

STARSTAR

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%

21

Xi’an 2006

STARSTAR

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)

22

Xi’an 2006

STARSTAR

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

23

Xi’an 2006

STARSTAR

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)