Strangeness

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Strangeness

• Dieter Röhrich
• Fysisk institutt, Universitetet i Bergen
• Yields and ratios
• Energy dependence of strangeness production
• Centrality dependence of strangeness production
• Open questions

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Experiments
midrapidity all y
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Short-lived resonances
?sNN 200 GeV
AuAu 40 to 80
STAR Preliminary
STAR Preliminary
?0 f0 K0S ? K0
0.2 ? pT ? 0.9 GeV/c y ? 0.5
AuAu minimum bias
pT ? 0.2 GeV/c y ? 0.5
Statistical error only
Statistical error only

• what about central AuAu collisions?

Patricia Fachini
Quark Matter 2002
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Observables

• Selected topics
• Rapidity distributions
• Yields and ratios
• chemical freeze-out
• Transverse mass spectra
• thermal freeze-out temperature and flow
• Correlations and flow

T. Ullrich
S. Voloshin
S. Pratt
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Rapidity Distributions

• SPS NA49 (40, 80, 158 AGeV)
• RHIC BRAHMS (?sNN 200 GeV)

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Comparison NA57 and NA49
Midrapidity yields and ratios are consistent
pT gt 0, ?y-ycm?lt 0.5
Quark Matter 2002, Nantes
V. Manzari, INFN Bari, Italy
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Net protons vs rapidity at RHIC
BRAHMS
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I.G.Bearden, Niels Bohr Institute
20 July 2002
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Rapidity density at RHIC (0-10 central)

Djamel Ouerdane - BRAHMS Collaboration
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Rapidity Distributions at RHIC

• Net baryon central plateau (y0 to almost y2)
• Pion and kaon spectra can be fitted by a single
  Gaussian
• Integrated yields are consistent with
  dNcharged/d? distributions
• 4?-ratios
• K/? ? 18
• K-/?- ? 14

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Particle/Particle vs rapidity
BRAHMS
BRAHMS, submitted to PRL 12/07/02 nucl-ex/0207006
I.G.Bearden, Niels Bohr Institute
20 July 2002
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Becattini T170, gs1 PBM (PhysLettB518 (2000)41)
predicts y0 ratios almost exactly K-/K exp(2m
s/T)(pbar/p)1/3 F. Becattini, J. Cleymans, A.
Keranen, E. Suhonen, K. Redlich, Phys.Rev. C64
(2001) 024901
BRAHMS, submitted to PRL 12/07/02 nucl-ex/0207006
BRAHMS
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I.G.Bearden, Niels Bohr Institute
20 July 2002
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Energy dependence

• K/?
• ?/?
• Short-lived resonances
• Hyperon ratios
• Statistical models

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K/? at RHIC
STAR Preliminary

• Midrapidity ratios
• Similar ratios from PHENIX and BRAHMS

K/p
K/K-
GeV
Quark Matter 2002 O. Barannikova, F. Wang
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Strangeness K/? systematics with
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Net proton rapidity distribution

• SPS
• central (6) PbPb, 158 GeV/nucl.
• NA49

• RHIC
• central (10) AuAu, ?sNN 200 GeV
• BRAHMS

G. Cooper et al. (NA49 Collaboration), Nucl.
Phys. A661 (1999) 362c-365c
J.H. Lee, BRAHMS
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The K0 story
STAR Preliminary
pp ? uncorrected for trigger bias and vertex
finding efficiency

• K0/K suppressed in AA versus pp
• f/K0 appears enhanced versus pp

STAR QM Talks E. Yamamoto and P. Fachini
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K0/?- Energy and System Dependence

• AuAu K0/?- at RHIC ? comparable to those at
  pp and ee- ? no enhancement in contradiction to
  other strange particles (K, ?, ?, ?, ?)
• ?sNN 130 GeV at RHIC ? statistical and
  systematic errors added in quadrature
• ?sNN 200 GeV at RHIC ? statistical error
  only

STAR Preliminary
Patricia Fachini
Quark Matter 2002
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Strangeness Production
Is Omega production well described ?
130 GeV predictions from thermal fit
(using all ratios except X/h-, W/h-, W/X)
Thermal Statistical (M.Kaneta, Poster
Session) Tch 17010 MeV mB 4810 MeV mS
2.35.1 MeV gS 0.990.11


SPS
RHIC
200 GeV data
1) Omegas at 130 GeV fit in thermal model 200
GeV Omegas results are still preliminary 2)
Production Yields relative to h- are close to
the SPS ones

Systematic errors 15
Strangeness Production Models see
J.Castillo talk on Xi production
Quark Matter 2002 - Nantes
Christophe Suire
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Sensitivity to Mixed Hadron Ratios
STAR Preliminary
?sNN130 GeV
10 central
10 Central
Models are in agreement with experimental data!

• Braun-Munzinger et al.Phys. Lett. B518

• Capella et al.hep-ph/0205014

• Levai et al.hep-ph/0112137

• Rafelski et al. hep-ph/0206145

Javier Castillo
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Ratios, experiment vs. a model
Central 130 GeV AuAu Preliminary Data
Agreement between model and data is very good!
STAR Preliminary
Thermal fits to mid-rapidity spectra have caveats
regarding non-4p measurements (local vs. global
equilibrium, boost-invariance). M. Kaneta and
N. Xu, J. Phys. G27 (2001) 589
STAR QM Poster M. Kaneta
Gene Van Buren
STAR Collaboration
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Centrality Dependence of Strangeness
Production

• Common scaling for central CC, SiSi, SS and
  peripheral PbPb
• Strangeness enhancement pattern

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Centrality dependence L, X and W yields _at_ 160
GeV
Black bars systematic errors
Quark Matter 2002, Nantes
V. Manzari, INFN Bari, Italy
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Strangeness enhancement and canonical suppression
Prediction for 40 AGeV
A. Tounsi
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Open Questions

• Contradicting figures missing figures
• W-, W inverse slope
• discrepancies in slopes and yields for F? K-K
  (F? e-e) and F? ?-?

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Comparison NA49 and WA97/NA57
WA97/NA57
NA49
T? 250 MeV
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Earlier Freeze-Out?
Central Collisions
Reminder Slope parameters from exp. Mt fits in
limited (high) mt-range
STAR Preliminary
Linear increase with particle mass ? Transverse
flow
Flattening of inverse slope parameter ? Earlier
freeze-out? ? Transverse flow
Slope parameter vs particle mass misleading Bett
er Flow fit to many spectra, HBT,..
Exponential fits except p
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f-Production Hadronic versus Leptonic Decay
Channel

• Different decay channels
• NA49 F? K-K
• NA50 F? ?-?
• Transverse momentum spectrum
• fit 1/mTdn/dmT exp(-mT/T)
• (NA49 3.0ltylt3.8)

significant differences in slopes and yields
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Resonance suppression by rescattering
30 effect not sufficient to explain measured
difference
M. Bleicher
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? ? KK- Invariant Mass
Yield
Au Au ?sNN 200 GeV Centrality 40 80

mass GeV/c2

• S 218 ? 24
• S/B 1/2

mass GeV/c2
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? ? ee- Mass Spectrum
Au Au ?sNN 200 GeV Minimum bias

mass GeV/c2
S/B 1/20
mass GeV/c2
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Minimum bias dN/dy

• ? ? KK- (TOF)
• ? ? ee-
• Consistent within present error

stat syst
Preliminary
stat syst
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Summary

• Comprehensive set of data
• Rapidity spectra at SPS and RHIC
• Short-lived resonances
• Statistical models describe particle ratios
• Complex centrality dependence of strangeness
  enhancement pattern
• Omega flow
• Phi puzzle