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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