System Size and Energy Dependence of Strangeness Production

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System Size and Energy Dependence of Strangeness
Production
Sevil Salur Yale University for the STAR
Collaboration
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Outline

• pT spectra and kinetic freeze-out of particles .
• Investigation of strange particle yields and
  ratios.
• Study of resonances
• (thermal vs chemical freeze-outs )
• Comparison of RHIC and SPS yields
• Strangeness enhancement
• (Energy dependence source type)
• RAA comparison with RCP and RdAu
• Investigation of strangeness ordering.
• Is there a scaling in AuAu production for the
  strange quarks? N Participants vs N Binary ?

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The Corrected Strange Particle Spectra
Y-4 AuAu and Y-5 CuCu is in progress !
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Tkinetic vs Transverse velocity (lt?Tgt)
Most Central Collisions

• Temperature Tkinetic is higher for baryons with
  higher strange quark content for Blast-wave fits.
• Spectral shapes are different.

T100 MeV
T132 MeV

• p,K, p lt?Tgt at 200 GeV gt 62 GeV Tkin at
  200 GeV 62 GeV
• X, W lt?Tgt at 200 GeV 62 GeV Tkin at
  200 GeV gt62 GeV

Tkinetic from a Blast-Wave is not same as
the Temperature from a Hydro Model.
QM Poster J.Speltz
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Strange Baryon Production and Collision Energy
AuAu
PbPb
STAR Preliminary

• s-Baryon production is constant at
  mid-rapidity.

• ?s-Baryon rises smoothly at mid-rapidity.

• ?s-Baryon production equals s-Baryon at RHIC
  Energies!

• s-Baryon Resonance follow the same trend.

QM Poster M.MunhozJ.Takahashi
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Strange Particle Ratios vs System Size
?L/L ratios are approximately independent of the
system size at RHIC energies.
Re-scattering and regeneration is needed ! Dt gt
0, constant for different centralities! Regenerati
on s(K) gt s(L)
QM Poster C Markert, D. Mishra
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System Size Dependence at 200 GeV
Redlich et al.
L and X yields in AuAu relative to pp
rises.
Canonical suppression increases with
increasing strangeness
L and X are not flat
Correlation volume not well modelled by Npart
Is the scaling more important than normalization ?
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s-Quarks Have Different Scaling!
Scaling according to quark content?
u, d scale with Npart already
observed. s scale with Nbin
appears better for strange particles.
Normalized to central data

• K0s 1/2Npart 1/2Nbin
• p Npart
• L 2/3Npart 1/3Nbin
• 1/3Npart 2/3Nbin
• f Nbin
• W Nbin

Does strangeness see a significant NBin
contribution?
Npart
f is puzzling!
QM Poster H. Caines
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Nuclear Modification Factor Rcp
vsNN200 GeV
Y-4 L, K0s
Baryon and meson suppression sets in at different
pT .
62 GeV Rcp shows less suppression.
Baryons and mesons are different !
QM Poster M.Lamont
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Nuclear Modification Factor Rcp
vsNN200 GeV
Y-4 L, K0s
Baryon and meson suppression sets in at different
pT .
Coalescence vs Fragmentation?
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RAA of Strange Particles
Mesons (h h-, K0s , f) follow similar
trends. Strange baryons dont show
suppression. Rcp ? Raa for strange baryons.
Canonical suppression in pp ?
0-5
STAR Preliminary
STAR Preliminary
s-quark
Ordering with strangeness content!
vsNN200 GeV
Particles with strange quarks scale differently
than non-strange!
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Does entropy drive the strangeness yield?
Enhancements are the same or even bigger at
RHIC than at SPS !
Is there a universal scaling?
Instead of Npart ? dNch/d? Correlated to the
entropy of the system!
SPS and RHIC data follows same curves
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Summary and Conclusions

• Transverse velocity ?T increases with collision
  energy.
• TFO (X) gt TFO (p) from Blast-wave but TFO (X)
  TFO (p) from Hydro
• ?s-Baryon production equals that of s-Baryon at
  RHIC energies.
• Baryon transport is independent of system size
  at RHIC energies.
• Rescattering and regeneration are required to
  model resonance production. Cross-sections and
  lifetimes vary (K vs L).
• Dt gt 0 between chemical and thermal freezeout
  for all centralities.
• RAA different than RCP - canonical suppression is
  being investigated in RAA and RdAu .
• Coalescence can explain the meson baryon
  difference at 62 GeV collisions too.
• Particles with s-quarks appear to scale
  differently than non-s quarks. Maybe s-quarks
  see a different correlation volume than light
  quarks?
• Yields scale with dNch/dh for SPS and RHIC
• (universal scaling?)

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Strange Poster Presentations

• 19 D. Mishra Measurement of 
  D and K production in dAu collisions at
  vsNN  200 GeV 
• 33 G. Van Buren  The Ratio S0/L at RHIC 
• 60 R. Bellwied Strange particle
  production mechanisms in pp collisions at RHIC
  
• 61 B. Bezverkhny Initial studies of two
  particle azimuthal correlations using X baryons
  in collisions at RHIC
• 67 L. Gaillard Identified two-hadron
  correlations at STAR using L, ?L and K0s
  with charged hadrons in AuAu at
  vsNN  200 GeV 
• 131  H. Caines  The effects of varying th
  e correlation volume on strangeness 
• 146 M. A. Lamont  High momentum strange baryon 
  anomalies in heavy ion collisions at
  RHIC  
• 151  C. Markert  The influence of medium pr
  operties on the resonance production in
  RHIC collision
• 152  C. M. Mironov STAR measurements of strange ha
  dron R AuAu and R dAu 
• 155  M. G. Munhoz  Measurements of K0s and ?L pro
  duction in collisions at 
• vsNN   62 GeV AuAu 
• 163  F. Simon Forward L production and 
  nuclear stopping power in dAu 
• collisions at RHIC
• 164  J. Speltz Energy dependence syste
  matics of strange and multi-strange particle
  production 
• 167 A. Tang  Strangelet search at RHIC 
  

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• EXTRAS

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Nuclear Modification Factor RdAu
vsNN200 GeV
Cronin Effect might explain R dAu above 1 Less so
for mesons than baryons !
Resonances follow a similar trend !
QM Poster C. Mironov