Modern Nuclear Physics with STAR @ RHIC:

Recreating the Creation of the Universe

Rene BellwiedRene BellwiedWayne State UniversityWayne State University((bellwied@physics.wayne.edubellwied@physics.wayne.edu))

Lecture 1: Why and How ?Lecture 1: Why and How ? Lecture 2: Bulk plasma matter ?Lecture 2: Bulk plasma matter ?

(soft particle production)(soft particle production) Lecture 3: Probing the plasmaLecture 3: Probing the plasma

(via hard probes)(via hard probes)

What is our mission ?• Discover the QGP

• Find transition behavior between an excited hadronic gas and another phase

• Characterize the states of matter • Do we have a hot dense partonic phase and how

long does it live ?• Characterize medium in terms of density,

temperature and time• Is the medium equilibrated (thermal,

chemical)

The idea of two phase transitionsDeconfinementDeconfinement

The quarks and gluons deconfine because energy or The quarks and gluons deconfine because energy or parton density gets too high parton density gets too high (best visualized in the bag model). (best visualized in the bag model).

Chiral symmetry restorationChiral symmetry restorationMassive hadrons in the hadron gas are massless Massive hadrons in the hadron gas are massless partons in the plasma. Mass breaks chiral symmetry, partons in the plasma. Mass breaks chiral symmetry, therefore it has to be restored in the plasma therefore it has to be restored in the plasma

What is the mechanism of hadronization ? What is the mechanism of hadronization ? How do hadrons obtain their mass ? How do hadrons obtain their mass ? (link to LHC and HERA physics)(link to LHC and HERA physics)

What do we measure in a collider experiment ? particles come from the vertex. They have to traverse certain detectors but should not particles come from the vertex. They have to traverse certain detectors but should not

change their properties when traversing the inner detectors change their properties when traversing the inner detectors DETECT but don’t DEFLECT !!!DETECT but don’t DEFLECT !!! inner detectors have to be very thin (low radiation length): easy with gas (TPC), inner detectors have to be very thin (low radiation length): easy with gas (TPC),

challenge with solid state materials (Silicon).challenge with solid state materials (Silicon). Measurements: Measurements: - momentum and charge via high resolution - momentum and charge via high resolution

tracking in SVT and TPC tracking in SVT and TPC in magnetic field (and in magnetic field (and FTPC)FTPC) - PID - PID via dE/dx in SVT and TPC and time of flightvia dE/dx in SVT and TPC and time of flight in TOF in TOF and and Cerenkov light in RICHCerenkov light in RICH - PID of decay particles via - PID of decay particles via impactimpact parameter parameter from SVT and TPCfrom SVT and TPC

particles should stop in the outermost detectorparticles should stop in the outermost detector Outer detector has to be thick and of high radiation length (e.g. Pb/Scint calorimeter)Outer detector has to be thick and of high radiation length (e.g. Pb/Scint calorimeter) Measurements:Measurements: - deposited energy for event and specific particles- deposited energy for event and specific particles - e/h - e/h

separation via shower profileseparation via shower profile - photon via - photon via shower profileshower profile

What do we have to check ?

If there was a transition to a different phase, then this phase could If there was a transition to a different phase, then this phase could only last very shortly. The only evidence we have to check is the only last very shortly. The only evidence we have to check is the collision debris.collision debris.

Check the make-up of the debris:Check the make-up of the debris: which particles have been formed ?which particles have been formed ? how many of them ?how many of them ? are they emitted statistically (Boltzmann distribution) ?are they emitted statistically (Boltzmann distribution) ? what are their kinematics (speed, momentum, angular what are their kinematics (speed, momentum, angular

distributions) ?distributions) ? are they correlated in coordinate or momentum space ?are they correlated in coordinate or momentum space ? do they move collectively ?do they move collectively ? do some of them ‘melt’ ?do some of them ‘melt’ ?

Signatures of the QGP phase

Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. entropy (i.e. # of degrees of freedom). entropy (i.e. # of degrees of freedom).

The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the existing form of matter. existing form of matter.

In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity. In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity.

At the step some signatures dropAt the step some signatures drop

and some signatures riseand some signatures rise

Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. entropy (i.e. # of degrees of freedom). entropy (i.e. # of degrees of freedom).

The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the existing form of matter. existing form of matter.

In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity. In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity.

At the step some signatures dropAt the step some signatures drop

and some signatures riseand some signatures rise

For more detail see for example: J. Harris and B. Müller, Annu, Rev. Nucl. Part. Sci. 1996 46:71-107(http://arjournals.annualreviews.org/doi/pdf/10.1146/annurev.nucl.46.1.71)

Evidence: Some particles are suppressed If the phase is very dense (QGP) than certain particles get absorbedIf the phase is very dense (QGP) than certain particles get absorbed

?

If things are produced in pairs then one might make it out and the other one not.

Central Au + Au

Peripheral Au + Au

STAR Preliminary

If things require the fusion of very heavy rare quarks they might be suppressed in a dense medium

Evidence: Some particles are enhanced Remember dark matter ? Well, we didn’t find clumps of it yet, but we Remember dark matter ? Well, we didn’t find clumps of it yet, but we

found increased production of strange quark particlesfound increased production of strange quark particles

How do we know what happened ?

We have to compare to a system that did definitely We have to compare to a system that did definitely not go through a phase transition (a reference not go through a phase transition (a reference collision)collision)

Two options:Two options: A proton-proton collision compared to a Gold-A proton-proton collision compared to a Gold-

Gold collision does not generate a big enough Gold collision does not generate a big enough volume to generate a plasma phasevolume to generate a plasma phase

A peripheral Gold-Gold collision compared to a A peripheral Gold-Gold collision compared to a central one does not generate enough energy central one does not generate enough energy and volume to generate a plasma phaseand volume to generate a plasma phase

Kinematic variables of choice

Rapidity y = ln (E+pz/E-pz)= lorentz invariant ‘velocity’

Transverse momentum pt = sqrt (px2+py

2)

y = -6 0 +6

y=-1 y=1y=2.2

y=3.7

0.) Global observablesA.) particle production

B.) particle spectraC.) particle flow

D.) particle correlations

Lattice QCDQuarks and gluons are Quarks and gluons are

studied on a discrete studied on a discrete space-time lattice space-time lattice Solves the problem of Solves the problem of

divergences in pQCD divergences in pQCD calculations (which arise calculations (which arise due to loop diagrams)due to loop diagrams)

There are two order There are two order parametersparameters

aa

Ns3 N

1. The Polyakov Loop L ~ Fq2. The Chiral Condensate ~ mq

(F. Karsch, hep-lat/9909006)

/T4

T/Tc

Lattice Results Tc(Nf=2)=1738 MeVTc(Nf=3)=1548 MeV

0.5 4.5 15 35 GeV/fm375

T = 150-200 MeV ~ 0.6-1.8 GeV/fm3

R2

Assessing the Initial Energy Density: Calorimetry

Central Au+Au (Pb+Pb) Collisions:17 GeV: BJ 3.2 GeV/fm3

GeVBJ 4.6 GeV/fm3

200 GeV: BJ 5.0 GeV/fm3

Bjorken-Formula for Energy Density:PRD 27, 140 (1983) – watch out for typo (factor 2)

Time it takes to thermalize system (0 ~ 1 fm/c)

~6.5 fm

dy

dE

RT

Bj0

2

11

dydz 0Note: (RHIC) < (SPS)commonly use 1 fm/c in both cases

Assessing the Initial Energy Density: TrackingBjorken-Formula for Energy Density:

d

dN

m

mm

R

d

dN

m

m

dy

dN

ydy

dNm

dy

dE

dy

dE

R

ch

T

TBj

ch

T

ch

chT

T

TBj

21

2

2

02

21

2

2

02

12

311

hence and

1

0at 2

3

11

Gives interestingly always slightly smaller values than with calorimetry (~15% in NA49 and STAR).

The Problem with BJ BJ BJ is not necessarily a “thermalized” energy densityis not necessarily a “thermalized” energy density

no direct relation to lattice valueno direct relation to lattice valuerequires boost invariancerequires boost invariance

is not well defined and model dependentis not well defined and model dependentusually 1fm/c taken for SPSusually 1fm/c taken for SPS0.2 – 0.6 fm/c at RHIC ?0.2 – 0.6 fm/c at RHIC ?

system performs work psystem performs work p··dV dV realreal > > BJBJ from simple thermodynamic assumptions from simple thermodynamic assumptions roughly factor 2roughly factor 2

Latticec

Bj~ 4.6 GeV/fm3

Bj~ 23.0 GeV/fm3

Boost invariance based on rapidity distributions

So what is now ?

At RHIC energies, central Au+Au collisions:At RHIC energies, central Au+Au collisions:1.1. From Bjorken estimates via EFrom Bjorken estimates via ETT and N and Nchch: : > 5 GeV/fm > 5 GeV/fm33

2.2. From energy loss of high-pFrom energy loss of high-pTT particles: particles: ≈≈ 15 GeV/fm 15 GeV/fm33

3.3. From Hydromodels with thermalization: From Hydromodels with thermalization: centercenter ≈≈ 25 GeV/fm 25 GeV/fm33

All are rough estimates and model dependent (EOS, All are rough estimates and model dependent (EOS, ?) , no ?) , no information about thermalization or deconfinement. Methods not information about thermalization or deconfinement. Methods not completely comparablecompletely comparable

But are without doubt good enough to support that But are without doubt good enough to support that >> >> CC ≈≈ 1 GeV/fm 1 GeV/fm33

How do we use hadrons ?

• Discovery probes: • CERN: Strangeness enhancement/equilibration• RHIC: Elliptic flow• RHIC: Hadronic jet quenching

• Characterization probes:• Chemical and kinetic properties• HBT and resonance production for timescales• Fluctuations for dynamic behavior

Particle Identification in STAR

Chemical freeze-out

(yields & ratios)

inelastic interactions cease

particle abundances fixed (except maybe resonances)

Thermal freeze-out

(shapes of pT,mT spectra):

elastic interactions cease

particle dynamics fixed

Basic Idea of Statistical Hadronic Models• Assume thermally (constant Tch) and chemically (constant ni)

equilibrated system

• Given Tch and 's (+ system size), ni's can be calculated in a grand canonical ensemble

Particle production:Statistical models do well

We get a chemical freeze-out temperature and a baryochemical potential out of the fit

Ratios that constrain model parameters

Statistical Hadronic Models : Misconceptions

• Model says nothing about how system reaches chemical equilibrium

• Model says nothing about when system reaches chemical equilibrium

• Model makes no predictions of dynamical quantities

• Some models use a strangeness suppression factor, others not

• Model does not make assumptions about a partonic phase; However the model findings can complement other studies of the phase diagram (e.g. Lattice-QCD)

Thermalization in Elementary Collisions ?

Beccatini, Heinz, Z.Phys. C76 (1997) 269Seems to work rather well ?!

Thermalization in Elementary Collisions ? Is a process which leads to multiparticle production thermal?Is a process which leads to multiparticle production thermal? AnyAny mechanism for producing hadrons which evenly populates the free mechanism for producing hadrons which evenly populates the free

particle phase space will mimic a microcanonical ensemble.particle phase space will mimic a microcanonical ensemble. Relative probabilityRelative probability to find a given number of particles is given by the ratio to find a given number of particles is given by the ratio

of the of the phase-spacephase-space volumes P volumes Pnn/P/Pn’n’ = = nn(E)/(E)/n’n’(E) (E) given by statistics only. given by statistics only.

Difference between MCE and CE vanishes as the size of the system N Difference between MCE and CE vanishes as the size of the system N increases.increases.

This type of “thermal” behavior requires no rescattering and no interactions. The collisions simply serve as a mechanism to populate phase space without ever reaching thermal or chemical equilibrium

In RHI we are looking for large collective effects.

Statistics Thermodynamics

Ensemble of events constitutes a statistical ensemble T and µ are simply Lagrange multipliers

“Phase Space Dominance”

A+A We can talk about pressure • T and µ are more than Lagrange multipliers

p+p

Are thermal models boring ?Good success with thermal models in e+e-, pp, and AA collisions.Thermal models generally maketell us nothing about QGP, but (e.g. PBM et al., nucl-th/0112051):

Elementary particle collisions: canonical description, i.e. local quantum number conservation (e.g.strangeness) over small volume.Just Lagrange multipliers, not indicators of thermalization.Heavy ion collisions: grand-canonical description, i.e. percolation of strangeness over large volumes, most likely in deconfined phase if chemical freeze-out is close to phase boundary.

T systematics

it looks like Hagedorn was right! it looks like Hagedorn was right! if the resonance mass spectrum grows exponentially (and this if the resonance mass spectrum grows exponentially (and this

seems to be the case), there is a maximum possible temperature seems to be the case), there is a maximum possible temperature for a system of hadronsfor a system of hadrons

indeed, we don’t seem to be able to get a system of hadrons with a indeed, we don’t seem to be able to get a system of hadrons with a temperature beyond Ttemperature beyond Tmaxmax ~ 170 MeV! ~ 170 MeV!

filled: AAopen: elementary

[Satz: Nucl.Phys. A715 (2003) 3c]

Does the thermal model always work ?

Particle ratios well described by Tch = 16010 MeV, B = 24 5 MeV

Resonance ratios change from pp to Au+Au Hadronic Re-scatterings!

Dat

a –

Fit

()

Rat

io

Strange resonances in medium

Short life time [fm/c] K* < *< (1520) < 4 < 6 < 13 < 40

Red: before chemical freeze outBlue: after chemical freeze out

Medium effects on resonance and their decay products before (inelastic) and after chemical freeze out (elastic).

Rescattering vs. Regeneration ?

ResonanceProduction in p+p and Au+Au

Thermal model [1]:

T = 177 MeVB = 29 MeV

[1] P. Braun-Munzinger et.al., PLB 518(2001) 41 D.Magestro, private communication[2] Marcus Bleicher and Jörg Aichelin Phys. Lett. B530 (2002) 81-87. M. Bleicher, private communication

Rescattering and regeneration is needed !

UrQMD [2]

Life time [fm/c] :(1020) = 40 (1520) = 13 K(892) = 4 ++ = 1.7

Resonance yields consistent with a hadronic re-scattering stage

Generation/suppression Generation/suppression according to x-sectionsaccording to x-sections

p

*

K*

p

K

K

p

More

Less K*

Che

mic

al f

reez

e-ou

t

KK

Ok

L*/L

K*/K

f/K-

D/p

r/p

W. Broniowski et al., nucl-th/0306034

J. Stachel SQM2003

Central STAR AuAu 200 GeV

p

K

K*/K

0.1 0.2 0.3

Less *

Preliminary

Strangeness: Two historic QGP predictions restoration of restoration of symmetry -> increased production of ssymmetry -> increased production of s

mass of strange quark in QGP expected mass of strange quark in QGP expected to go back to current value (mto go back to current value (m SS ~ ~ 150 MeV ~ Tc)150 MeV ~ Tc)

copious production of ss pairs, mostly copious production of ss pairs, mostly by gg fusion by gg fusion

[[Rafelski: Phys. Rep. 88 (1982) 331]Rafelski: Phys. Rep. 88 (1982) 331][Rafelski-Müller: P. R. Lett. 48 (1982) 1066[Rafelski-Müller: P. R. Lett. 48 (1982) 1066]]

deconfinement deconfinement stronger effect for multi-strange stronger effect for multi-strange by using uncorrelated s quarks produced in independent partonic by using uncorrelated s quarks produced in independent partonic

reactions, faster and more copious than in hadronic phasereactions, faster and more copious than in hadronic phase strangeness enhancement increasing with strangeness contentstrangeness enhancement increasing with strangeness content

[Koch, Müller & Rafelski: Phys. Rep. 142 (1986) 167][Koch, Müller & Rafelski: Phys. Rep. 142 (1986) 167] Strangeness production depends strongly on baryon densityStrangeness production depends strongly on baryon density(i.e. stopping vs. transparency, finite baryo-chemical potential)(i.e. stopping vs. transparency, finite baryo-chemical potential)

q q s s

g g s s

N K

K N

Ethres 2ms 300 MeV

Ethres 530 MeV

Ethres 1420 MeV

Strangeness enhancement in B/B ratios

Baryon over antibaryon Baryon over antibaryon production can be a QGP production can be a QGP signature as long as the signature as long as the baryochemical potential is baryochemical potential is high (Rafelski & Koch, high (Rafelski & Koch, Z.Phys. 1988)Z.Phys. 1988)

• With diminishing baryochemical potential (increasing transparency) the ratios approach unity with or without QGP, and thus only probe the net baryon density at RHIC.

New RHIC data of baryon ratios

• The ratios for pp and AA at 130 and 200 GeV are almost indistinguishable. The baryochemical potentials drop from SPS to RHIC by almost an order of magnitude to ~50 MeV at 130 GeV and ~20 MeV at 200 GeV.

BRAHMS, PRL

nucl-ex/0207006

STAR p+p 200 GeV

Strangeness enhancement:Wroblewski factor evolution

Wroblewski factor

dependent on T and B

dominated by KaonsLines of constant S

<E>/<N> = 1 GeV

I. Increase instrange/non-strangeparticle ratiosII. Maximum isreached

III. Ratios decrease(Strange baryonsaffected more stronglythan strange mesons)

Peaks at 30 A GeV in AA collisions due to strong B dependence

mesons

baryons

hidden strangeness mesons

PBM et al., hep-ph/0106066

total

See P.Senger’s talk

Strangeness enhancement K/K/ – the benchmark for abundant strangeness production: – the benchmark for abundant strangeness production:

K/

K+/

[GeV]

The SPS ‘discovery plot’ (WA97/NA57)Unusual strangeness enhancement

N(wounded) N(wounded)

The switch from canonical to grand-canonical(Tounsi,Redlich, hep-ph/0111159, hep-ph/0209284)

The strangeness enhancement factors at the SPS (WA97) canbe explained not as an enhancement in AA but a suppression in pp.

The pp phase space for particle production is small. The volume is small and the volume term will dominate the ensemble (canonical (local)). The grand-canonical approach works for central AA collisions, but because the enhancements are quoted relative to pp they are due to a canonical suppression of strangeness in pp.

Strangeness enhancement factors at RHIC

Npart-scaling in Au-Au at RHIC -> lack of Npart scaling = no thermalization ?

Alternatives: no strangeness saturation in peripheral collisions (s = 1)

non-thermal jet contributions rise with centrality

Grandcanonical prediction

Identified particle spectra : p, p, K-,+, -,+, K0

s and

Identified Particle Spectra for Au-Au @ 200 GeV

BRAHMS: 10% centralPHOBOS: 10%PHENIX: 5%STAR: 5%

The spectral shape gives us:The spectral shape gives us: Kinetic freeze-out Kinetic freeze-out

temperaturestemperatures Transverse flowTransverse flow

The stronger the flow the less The stronger the flow the less appropriate are simple appropriate are simple exponential fits:exponential fits: Hydrodynamic models Hydrodynamic models

(e.g. Heinz et al., (e.g. Heinz et al., Shuryak et al.) Shuryak et al.)

Hydro-like parameters Hydro-like parameters (Blastwave)(Blastwave)

Blastwave parameterization e.g.:Blastwave parameterization e.g.: Ref. : E.Schnedermann Ref. : E.Schnedermann

et al, PRC48 (1993) et al, PRC48 (1993) 24622462

Explains: spectra, flow & Explains: spectra, flow & HBT HBT

“Thermal” Spectra

TE

TT

Eeddmmdy

dN

dp

NdE /)(

3

3

Invariant spectrum of particles radiated by a thermal source:

where: mT= (m2+pT2)½ transverse mass (Note: requires knowledge of mass)

= b b + s s grand canonical chem. potentialT temperature of source

Neglect quantum statistics (small effect) and integrating over rapidity gives:

TmT

TmTT

TT

TT emTmKmdmm

dN /1 )/(

R. Hagedorn, Supplemento al Nuovo Cimento Vol. III, No.2 (1965)

TmT

TT

Temdmm

dN /

At mid-rapidity E = mT cosh y = mT and hence:

“Boltzmann”

“Thermal” Spectra (flow aside)

N.B. Constituent quark and parton recombination models yield exponential spectra with partons following a pQCD power-law distribution. (Biro, Müller, hep-ph/0309052) T is not related to actual “temperature” but reflects pQCD parameter p0 and n.

Describes many spectra well over several orders of magnitude with almost uniform slope 1/T

• usually fails at low-pT

( flow)• most certainly will fail at high-pT ( power-law)

T-mT

TT

Temdmm

dN /

“Thermal” spectra and radial expansion (flow)

• Different spectral shapes for particles of differing mass strong collective radial flow

• Spectral shape is determined by more than a simple T

• at a minimum T, T

mT

1/m

T d

N/d

mT light

heavyT

purely thermalsource

explosivesource

T,

mT1/

mT d

N/d

mT light

heavy

Thermal + Flow: “Traditional” Approach

shift) (blue for

1

1

for 2

mpT

mpmT

TT

T

Tth

TTth

measured

1. Fit Data T 2. Plot T(m) Tth, T

is the transverse expansion velocity. With respect to T use kinetic energy term ½ m 2

This yields a common thermal freezeout temperature and a common .

Assume common flow pattern and commontemperature Tth

Hydrodynamics in High-Density Scenarios Assumes local thermal equilibrium (zero mean-free-path limit) Assumes local thermal equilibrium (zero mean-free-path limit)

and solves equations of motion for fluid elements (not particles)and solves equations of motion for fluid elements (not particles) Equations given by continuity, conservation laws, and Equations given by continuity, conservation laws, and Equation of Equation of

State (EOS)State (EOS) EOS relates quantities like pressure, temperature, chemical EOS relates quantities like pressure, temperature, chemical

potential, volume = potential, volume = direct access to underlying physicsdirect access to underlying physics

Kolb, Sollfrank & Heinz,hep-ph/0006129

Hydromodels can describe mT (pT) spectra

• Good agreement with hydrodynamic prediction at RHIC & SPS (2d only)• RHIC: Tth~ 100 MeV, T ~ 0.55 c

Blastwave: a hydrodynamic inspired description of spectra

R

s

Ref. : Schnedermann, Sollfrank & Heinz,PRC48 (1993) 2462

Spectrum of longitudinal and transverse boosted thermal source:

r

n

sr

TTT

TT

R

rr

T

mK

T

pImdrr

dmm

dN

tanh rapidity)(boost angleboost and

)( ondistributi velocity transverse

with

cosh

sinh

1

R

0 10

Static Freeze-out picture,No dynamical evolution to freezeout

The Blastwave Function

• Increasing T has similar effect on a spectrum as increasing s

• Flow profile (n) matters at lower mT! • Need high quality data down to low-mT

Heavy (strange ?) particles show deviations in basic thermal parametrizations

STAR preliminary

Blastwave fitsSource is assumed to be:

• In local thermal equilibrium• Strongly boosted • , K, p: Common thermal

freeze-out at T~90 MeV and <>~0.60 c

• : Shows different thermal freeze-out behavior:

• Higher temperature• Lower transverse flow

Probe earlier stage of the collision, one at which transverse flow has already developed If created at an early partonic stage it must show significant elliptic flow (v2)

Au+Au sNN=200 GeV

STAR Preliminary

68.3% CL 95.5% CL 99.7% CL

Blastwave vs. Hydrodynamics

Tdec = 100 MeV

Kolb and Rapp,PRC 67 (2003)

044903.

Mike Lisa (QM04): Use it don’t abuse it ! Only use a static freeze-out parametrization when the dynamic model doesn’t work !!

Collective Radial Expansion

r r increases continuouslyincreases continuously

TTthth

saturates around AGS energysaturates around AGS energy

Strong collective radial expansion at RHIC high pressure high rescattering rate Thermalization likely

Slightly model dependenthere: Blastwave model

From fits to , K, p spectra:

Elliptic Flow (in the transverse plane)

for a mid-peripheral collision

Dashed lines: hard sphere radii of nuclei

Reactionplane

In-planeOu

t-o

f-p

lan

e

Y

X

Re-interactions FLOW Re-interactions among what? Hadrons, partons or both?

In other words, what equation of state?

Flow

Flo

w

v2 measurements (Miklos’ Favorite)

Multistra

nge v2 es

tablishes

partonic

collecti

vity ?

Lifetime and centrality dependence from (1520) / and K(892)/K

Model includes: • Temperature at chemical freeze-out• Lifetime between chemical and thermal freeze-out• By comparing two particle ratios (no regeneration)

results between : T= 160 MeV => > 4 fm/c (lower limit !!!) = 0 fm/c => T= 110-130 MeV

(1520)/ = 0.034 0.011 0.013

K*/K- = 0.20 0.03 at 0-10% most central Au+Au

G. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239

Life time:K(892) = 4 fm/c (1520) = 13 fm/c

preliminary

More resonance measurements are needed to verify the model and lifetimes

Blast wave fit of ,K,p (Tkin +Tchem

~ 6 fm/c Based on entropy: t ~ (Tch/Tkin – 1) R/s

does not change much with centralitybecause slight T reduction is compensated by slower expansion velocity in peripheral collisions.

Time scales according to STAR data

dN/dt

1 fm/c 5 fm/c 10 fm/c 20 fm/ctimeChemical freeze out

Kinetic freeze out

Balance function (require flow)Resonance survival

Rlong (and HBT wrt reaction plane)

Rout, Rside

hadronization

initial state

pre-equilibrium

QGP andhydrodynamic expansion

hadronic phaseand freeze-out

PCM & clust. hadronization

NFD

NFD & hadronic TM

PCM & hadronic TM

CYM & LGT

string & hadronic TM

Initial energy density high enough to produce a QGPInitial energy density high enough to produce a QGP

10 GeV/fm10 GeV/fm33 (model dependent)(model dependent)

High gluon density High gluon density dN/dy ~ dN/dy ~ 80080012001200

Proof for Proof for high density matterhigh density matter but not for QGP but not for QGP

Summary: global observables

Statistical thermal models appear to work well at SPS and RHICStatistical thermal models appear to work well at SPS and RHIC Chemical freeze-outChemical freeze-out is close to T is close to TCC

Hadrons appear to be bornHadrons appear to be born

into equilibrium at RHIC (SPS)into equilibrium at RHIC (SPS) Shows that what we observe is Shows that what we observe is

consistent with consistent with thermalizationthermalization Thermal freeze-outThermal freeze-out is common is common

for all particles if radial flowfor all particles if radial flow

is taken into account.is taken into account.

T and T and are correlated are correlated

Fact that you derive T,Fact that you derive T,TT is is

no direct proof but it is consistent withno direct proof but it is consistent with thermalization thermalization

Summary of particle identified observables

Conclusion There is no “ “ in bulk matter propertiesThere is no “ “ in bulk matter properties However:However:So far all pieces So far all pieces pointpoint

indeed to QGP formationindeed to QGP formation

- collective flow- collective flow

& radial& radial

- thermal behavior- thermal behavior

- high energy density- high energy density

- strange particle production enhancement- strange particle production enhancement

elliptic