Transcript Introduction - Duke University

Multi-Strange baryons in Au + Au
collisions at s NN  130 GeV
Probing thermal freeze-out conditions
via multi-strange baryons
Javier Castillo
• Introduction
• The data :
LBNL
• Multi strange baryons
transverse mass spectra
• Average transverse
momentum <p>
• Thermal model fits
• Conclusion & Outlook
SQM - Atlantic Beach, NC - 13/03/2003
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Introduction
Time
1) Initial Condition
- baryon transfer
- ET production
- partons dof
2) System Evolves
- parton/hadron
expansion
3) Bulk Freeze-out
- hadrons dof
- interactions stop
Plot by S. Bass
Q. Collectivity?
Tools:
Problem:
PCM
& clust. hadronizationApproach:
• Transverse Flow
• Flow is
• Probes
NFD “insensitive” to
• Elliptic Flow
additive
hadronic
stage (,,,D,J/)
NFD & hadronic TM
CYM & LGT
SQM - Atlantic Beach, NC - 13/03/2003
string & hadronic
TM Castillo
Javier
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0 - 10%
Au+Au sNN=130 GeV
Invariant mass distributions
Reconstructed by a topological method:
Poster by Magali Estienne (SUBATECH)
sNN  130GeV
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STAR Preliminary
Corrected for reconstruction efficiency and detector
acceptance by the Embedding Monte Carlo technique
SQM - Atlantic Beach, NC - 13/03/2003
Au+Au sNN=130 GeV
Transverse mass spectra @ 130 GeV
Covered p region:
•  ~ 75 %
•  ~ 66 %
Javier Castillo
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<p> centrality dependence
P
K

STAR Preliminary
Au+Au sNN=130 GeV
• , K, P : <p> increase
with collision centrality
• , K, P : <p> centrality
dependence is stronger for
heavier particles
→ Consistent with collective
flow picture.
•  : <p> show no
dependence with h→ Different flow behavior!
(Consistent with  tendency
at 200 GeV - J. Ma talk)
SQM - Atlantic Beach, NC - 13/03/2003
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<p> for central collisions
STAR Preliminary
Au+Au sNN=130 GeV
<p> from a thermal fit to
, K, P,  transverse mass
spectra
• , K, P,  : <p> increase
with particle mass as described
by thermal models
• ,  : <p> deviates from
common thermal freeze-out
picture!
• Early thermal freeze-out ?
• Early collectivity ?
SQM - Atlantic Beach, NC - 13/03/2003
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Thermal Model Fit
Source is assumed to be:
• In local thermal equilibrium
• Strongly boosted
Thermal freeze-out temperature Tfo
Transverse flow rapidty  (velocity )
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Thermal freeze-out parameters
Blast Wave fits – Linear profile
Tfo - (), 1 and 2  contours
,

• , K, P, : Common thermal
freeze-out at T~100 MeV and
<>~0.52c
• , : Show different thermal
freeze-out behavior:
• Higher temperature
• Lower transverse flow
,K,P,
,K,P, • Driven mainly by  - Need
high statistics  measurement
,K,P,
STAR Preliminary
Transverse flow is still
significant, when does it
develop?
Au+Au sNN=130 GeV
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What to expect in case of early collectivity?
• Stronger transverse flow at RHIC
than at SPS energies
?
• At both energies multi-strange
baryons deviates from common
transverse flow picture
• At SPS , J/, ’ slope
parameter saturates
• At RHIC, new increase ?
Early collectivity? Then:
1) Increase of T for , D, J/ …
2) Non-zero values of v2 for , 
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Conclusions, Outlooks
• Hints for earlier collectivity
• Looking for a clear picture:
– Precise centrality
–  &  show different thermal
freeze-out behavior than , K,
dependence of  thermal
freeze-out parameters
P, 
STAR Preliminary
• Higher Tfo
– High statistics  (D,J/)
transverse flow measurement
• Smaller (but significant)
transverse flow
– Elliptic flow measurement
for  and 
– No or little centrality
dependence of <p> for 
(and )
This is coming!
C. Suire – QM02
SQM - Atlantic Beach, NC - 13/03/2003
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BACK-Ups
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Transverse mass spectra – BlastWave fits
• ,  minimum
• , K, P,  minimum
• , K, P,STAR
 upper-left
of 2  contour
Preliminary
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