Bulk signatures & Bulk signatures & propertiesproperties(soft particle (soft particle production)production)

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

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

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

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

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

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

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

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:

Dynamics indicate common freezeout for most particles

Chemical FO temperature

About 70 MeV difference between Tch and Tth: hadronic phase

Collective anisotropic flow

x

yz

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

Anisotropic FlowAnisotropic Flow

A.Poskanzer & S.Voloshin (’98)

z

x

x

y

Transverse plane Reaction plane

0th: azimuthally averaged dist. radial flow1st harmonics: directed flow2nd harmonics: elliptic flow…

“Flow” is not a good terminologyespecially in high pT regions

due to jet quenching.

Hydrodynamics describes the data

Hydrodynamics:strong coupling,small mean free path,lots of interactionsNOT plasma-like

Strong collective flow:elliptic and radial expansion withmass ordering

v2 measurements

Multistra

nge v2 es

tablishes

partonic

collecti

vity ?

# III: The medium consists of constituent quarks ?

baryonsbaryons

mesonsmesons

Ideal liquid dynamics –reached at RHIC for the 1st time

A more direct handle? elliptic flow (velliptic flow (v22) and other measurements (not ) and other measurements (not

discussed) discussed) evidence towards QGP at RHIC evidence towards QGP at RHIC indirect connection to geometryindirect connection to geometry

Are there more direct handles on the space-time Are there more direct handles on the space-time geometry of collisions?geometry of collisions? yes ! Even at the 10yes ! Even at the 10-15-15 m / 10 m / 10-23-23 s scale ! s scale !

What can they tell us about the QGP and system What can they tell us about the QGP and system evolution?evolution?

Volumes & Lifetimes= 2nd Law Thermodynamics Ideal GasIdeal Gas Relativistic Fermi/Bose GasRelativistic Fermi/Bose Gas=0=0

Pions (Pions (33) vs. QGP () vs. QGP (3737))

NkTPV

3

2

)(1523

87 )(

cfb VTnnS

0

3),,( 0

f

b

n

n

24

162322

82

flavorcolorspin

colorspin

f

b

n

n

.3

370

constT

qgphadronize VVt

S

222111 p)xr(i22

p)xr(i11T e)p,x(Ue)p,x(U

Probing source geometry through interferometry(Hanbury-Brown & Twiss (HBT) – photons from stars

12 ppq

2

21

2121 )q(~1

)p(P)p(P)p,p(P

)p,p(C

C (Q

inv)

Qinv (GeV/c)

1

2

0.05 0.10

Width ~ 1/R

Measurable! F.T. of pion source

)xx(iq2

*21

*1T

*T

21e1UUUU

Creation probability (x,p) = U*U5 fm

1 m source(x)

r1

r2

x1

x2

{2

1

}e)p,x(Ue)p,x(U 212121 p)xr(i21

p)xr(i12

p1

p2

The Bottom line…if a pion is emitted, it is more likely to emit another

pion with very similar momentum if the source is small

experimentally measuring this enhanced probability: quite challenging

Bose-Einstein correlations

HBT (GGLP) Basics In the simplest approximation, the technique has not In the simplest approximation, the technique has not

changed since before most of you were bornchanged since before most of you were bornGoldhaber, Goldhaber, Lee, and Pais, PR 120:300 (1960)Goldhaber, Goldhaber, Lee, and Pais, PR 120:300 (1960)

For identical bosons/fermionsFor identical bosons/fermions

But this (plane wave) approximation neglects many effects

P(p1,p2;r1,r2) =

P(p1,p2)/P(p1)P(p2) = 1 + | (p1 - p2) |2~

Gaussian source in xi yields Gaussian correlation in conjugate variable qi=p1i-p2i

Who made first use of this pedagogic picture?

HBT Complexities We have neglectedWe have neglected

Final state interactionsFinal state interactionsCoulomb interactionCoulomb interactionStrong interactionStrong interactionWeak decaysWeak decays

Position-momentum correlationsPosition-momentum correlationsThings more subtle, such as special relativityThings more subtle, such as special relativity

State of the art analysis incorporates most of these, but not all

Correlation functions for different colliding systems

C2(

Qin

v)

Qinv (GeV/c)

STAR preliminary p+pR ~ 1 fm

d+AuR ~ 2 fm

Au+AuR ~ 6 fm

Different colliding systems studied at RHIC

Interferometry probes the smallest scales ever measured !

qout

qside

qlong

Reminder

Rsi

de

R long

Rout

x1

x2

12 ppq

p1

p2

q

12 pp2

1k

Two-particle interferometry: p-space separation Two-particle interferometry: p-space separation space-time separation space-time separation

RRsideside

RRoutout

Pratt-Bertsch (“out-side-long”) decomposition designed to help disentangle space & time

source sp(x) = homogeneity region [Sinyukov(95)]

connections with “whole source” always model-dependent

beam directi

on

More detailed geometryRelative momentum between pions is a vector can extract 3D shape information

1 2q p p

p2

p1

q1 2K p p

R long

RsideRout

Rlong – along beam direction

Rout – along “line of sight”

Rside – “line of sight”

STAR, PRL93 012301 (2004)

Measured final source shape

centralcollisions

mid-centralcollisions

peripheralcollisions

Expected evolution:

More informationRelative momentum between pions is a vector can extract 3D shape information

1 2q p p

p2

p1 1 2K p p

Rout

Rlong – along beam direction

Rout – along “line of sight”

Rside – “line of sight”

Rside

study as K grows…

Why do the radii fallwith increasing momentum ??

Geometric substructure?random (non-)system:

all observers measure the

“whole source”

Why do the radii fallwith increasing momentum ??

It’s collective flow !!

Direct geometrical/dynamical evidencefor bulk behaviour!!!

Specific predictions ofbulk global collective flow:

• space-momentum (x-p) correlations

• faster (high pT) particles come from

•smaller source

•closer to “the edge”

Flow-generated substructurerandom (non-)system:

all observers measure the

“whole source”

Timescales

Evolution of source shapeEvolution of source shape suggests suggests systemsystem lifetime is shorter than lifetime is shorter than

otherwise-successful theory predictsotherwise-successful theory predicts

Is there a more direct handle on timescales?Is there a more direct handle on timescales?

Disintegration timescaleRelative momentum between pions is a vector can extract 3D shape information

1 2q p p

p2

p1

q1 2K p p

Rout

Rlong – along beam direction

Rout – along “line of sight”

Rside – “line of sight”

Rside

increases with emission timescale

OUT

SIDE

R

R

Disintegration timescale - expectation3D 1-fluid Hydrodynamics

Rischke & Gyulassy, NPA 608, 479 (1996)

withtransition

withtransition

“” “”

Long-standing favorite signature of QGP:

• increase in , ROUT/RSIDE due to deconfinement confinement transition

• expected to “turn on” as QGP energy threshold is reached

Disintegration timescale - observation

4

6

8

4

6

8

1.0

1.25

1.5R

O (

fm)

RS (

fm)

RO

/ R

S

increasing collision energy

RHIC

• no threshold effect seen

• RO/RS ~ 1

Disintegration timescale - observation

PCM & clust. hadronization

NFD

NFD & hadronic TM

PCM & hadronic TM

CYM & LGT

string & hadronic TM

N()

Heinz & Kolb, hep-ph/0204061

• no threshold effect seen

• RO/RS ~ 1

• toy model calculations suggest very short timescales• rapid, explosive evolution• too explosive for “real” models

which explain all other data

An important space-time“puzzle” at RHIC

- actively under study

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

elliptic