DNP03, Tucson, Oct 29, 2003 1 Kai Schweda Lawrence Berkeley National Laboratory for the STAR...
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1 DNP03, Tucson, Oct 29, 2003
Kai Schweda
Lawrence Berkeley National Laboratory
for the STAR collaboration
Hadron Yields, Hadrochemistry,
and Hadronization in High Energy
Nuclear Collisions
2 DNP03, Tucson, Oct 29, 2003
Outline
Introduction / Motivation
Statistical Model - Tch, B, s
Experimental Results (SPS, RHIC, …)
Multi-strange hadron spectra and partonic
collectivity
Summary
3 DNP03, Tucson, Oct 29, 2003
Heavy Ion Collisions
PCM & clust. hadronization
NFD
NFD & hadronic TM
PCM & hadronic TM
CYM & LGT
string & hadronic TM
1) Initial condition: 2) System evolves: 3) Bulk freeze-out
-Baryon transfer - parton/hadron expansion - hadronic dof
- ET production - inel. interactions cease:
-Partonic dof particle ratios, Tch, B
- elas. interactions cease
Paticle spectra, Tth, <T>
Time
Plot: Steffen A. Bass, Duke University
5 DNP03, Tucson, Oct 29, 2003
Collision Geometry
x
z
Non-central Collisions
Au + Au sNN = 200 GeV
Uncorrected
• No direct measure of impact parameter
• Use track multiplicity to define collision
centrality
6 DNP03, Tucson, Oct 29, 2003
Particle IdentificationParticle Identification
Identify (multi-)strange particles in full azimuthal acceptance of STAR!
(ss)(ds)
(sss)(dss)(uds)
7 DNP03, Tucson, Oct 29, 2003
Chemical Freeze-out Model
Hadron resonance ideal gas
Compare particle ratios to experimental data
Qi : 1 for u and d, -1 for u and d
si : 1 for s, -1 for s
gi : spin-isospin freedom
mi : particle mass
All resonances and unstable particles are decayed
Refs. J.Rafelski PLB(1991)333P. Braun-Munzinger et al., nucl-th/0304013
Tch : Chemical freeze-out temperatureq : light-quark chemical potentials : strange-quark chemical potentialV : volume term, drops out for ratios!s : strangeness under-saturation factor
Density of particle i
8 DNP03, Tucson, Oct 29, 2003
Central Collisions at RHIC
1) Particle ratios vary by factor ~100
2) Statistical model reproduces data well, 2= /dof
3) Tch = 170 10 MeV, B = 4010 MeV; s = f(B), s 1
4) Strangeness fully equilibrated at RHIC!
P. Braun-Munzinger et al., nucl-th/0304013.
Au+Au @130GeV
9 DNP03, Tucson, Oct 29, 2003
Centrality Dependence*
At RHIC, Au+Au@130GeV
hadronization occurs at Tch 17010 MeV
full strangeness equilibration in central collisions, s = 1 !
Red: fit with multi-strange hadronsBlue: fit w/o multi-strange hadrons
*M. Kaneta, QM2002, Nantes, France.
10 DNP03, Tucson, Oct 29, 2003
Bombarding energies
Te
mp
era
ture
(G
eV
)
Ch
em
ica
l po
ten
tial (
Me
V)
Bombarding energies
Beam-Energy Dependence
With higher collision energies:
Tch saturates close to phase boundary,
B decreases approaching net-baryon free!
At RHIC, s = 1.0 (at SPS: 0.75) full strangeness equilibration at RHIC
11 DNP03, Tucson, Oct 29, 2003
Chemical Freeze-out SystematicsChemical Freeze-out Systematics
At SPS and RHIC: hadron yields freeze-
out close to phase boundary !
Approaching net-baryon free !
Lattice QCD predictions
Neutron star
12 DNP03, Tucson, Oct 29, 2003
Chemical Freeze-out (cont’d)T
empe
ratu
re (
MeV
)
Baryon-Chemical potential B(GeV)
<E>/<N> = 1GeV
Inelastic interactions cease
at <E>/<N> = 1GeV*
At RHIC, chemical and
critical conditions coincide
Inelastic interactions
reduced at RHIC?
*J. Cleymans and K. Redlich, Phys. Rev. Lett. 81, 5284 (1998).
13 DNP03, Tucson, Oct 29, 2003
Resonance Ratios
K* lifetime ~ 4fm/c
K* K +
K*/K ratio decreases by
factor two
hadronic re-scattering
!
measure more
resonances to study
collision dynamics
14 DNP03, Tucson, Oct 29, 2003
Elementary p+p Collisions
Low multiplicities
use canonical esemble
Strangeness has to
be conserved locally
particle yields are
well reproduced
Strangeness not
equilibrated !
(s = 0.5)
Statistical Model Fit: F. Becattini and U. Heinz, Z. Phys. C 76, 269 (1997).
15 DNP03, Tucson, Oct 29, 2003
Hadron Yields
At RHIC:
- chemical freeze-out close to phase boundary,
Tch ~17010 MeV
- approaching net-baryon free, B = 4010 MeV
- full strangeness equilibration!
AT SPS:
- strangeness not fully equilibrated (s = 0.75)
Information about pre-hadronic phase?
16 DNP03, Tucson, Oct 29, 2003
Pressure, Flow, …Pressure, Flow, …
pdVdUd Thermodynamic identity
– entropy p – pressureU – energy V – volume= kBT, thermal energy per dof
In A+A collisions, interactions among constituentsand density distribution lead to: pressure gradient collective flow
number of degrees of freedom (dof) Equation of State (EOS) cumulative – partonic + hadronic
17 DNP03, Tucson, Oct 29, 2003
1) Compare to 1) Compare to , , KK, and , and p,p, multi-strange particles multi-strange particles ,, are found at higher Tare found at higher T and lower <and lower <TT>>
Collectivity prior to Collectivity prior to hadronization hadronization
2) Sudden single freeze-out*2) Sudden single freeze-out*Resonance decay lower TResonance decay lower Tfofo
for (for (, , KK, , pp)) Collectivity prior to Collectivity prior to
hadronizationhadronization
Partonic Partonic Collectivity !Collectivity !
Kinetic Freeze-out
Data: Data: STAR preliminary Au+Au@200GeV: Nucl. Phys. A715, 129c(2003).*A. Baran, W. Broniowski and W. Florkowski; nucl-th/0305075
18 DNP03, Tucson, Oct 29, 2003
Slope Parameters vs Mass
gluon
tii
n
pm
00
22
-exp
Small X-section limit: , J/
sensitive to collectivity at parton level?
At high energy, high gluon density leads to parton flow
2
thermal massTSlope
19 DNP03, Tucson, Oct 29, 2003
Elliptic Flow, vElliptic Flow, v22
y
x
py
px
coordinate-space-anisotropy momentum-space-anisotropy
Initial/final conditions, dof, EOS
1i
Ritttt
))cos(i(2v1dydpp
dN
2
1
dyddpp
dN
20 DNP03, Tucson, Oct 29, 2003
Multi-Strange Baryons v2
Multi-strange baryons
show collectivity !
Partonic collectivity Partonic collectivity
at RHIC!at RHIC!
21 DNP03, Tucson, Oct 29, 2003
Quark Coalescence
Exp. data consistent with quark
coalescence scenario
Partonic collectivity at RHIC!Partonic collectivity at RHIC!
Pentaquark Pentaquark
(uudds), n=5 ?(uudds), n=5 ?
Z. Lin et al., PRL, 89, 202302(02)R. Fries et al., nucl-th/0301087D. Molnar et al. nucl-th/0302014
22 DNP03, Tucson, Oct 29, 2003
Summary
Statistical model describes hadron production at RHIC
Tch ~17010MeV, B = 4010 MeV
strangeness fully equilibrated
Partonic Collectivity / Quark Coalescence !
Measure centrality dependence yields, spectra and v2
of , K*, , , …, D0, Ds, c,
to confirm partonic collectivity
probe thermalization