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Bulk signatures & properties (soft particle production). Does the thermal model always work ?. Data – Fit ( s ) Ratio. Particle ratios well described by T ch = 160 10 MeV, m B = 24 5 MeV Resonance ratios change from pp to Au+Au Hadronic Re-scatterings!. - PowerPoint PPT Presentation
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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