Mixed Hadron Ratios from STAR

1
Mixed Hadron Ratios from STAR
Rene Bellwied, Wayne State University, for the
STAR Collaboration

• PID spectra in STAR
• Baryon/anti-baryon ratios
• Mixed hadron ratios
• Statistical models
• Chemical fits
• Quark coalescence
• Sudden hadronization
• Dynamical models
• Conclusions

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p / K / p - slope parameters
dE/dx-analysis with TPC
dE/dx , kink, V0 analysis comparison for charged
and neutral Kaons
mid-rapidity y0.1
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Slope Parameters via V0 PID (y0.5)
Preliminary pt 0.5-3.5 GeV/c
Larger pt-range than dE/dx, better
characterization of flow
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STAR B/B Ratios
Ratio approaching 1.0 as strangeness content
increases
STAR preliminary
0.94 0.13
Ratios calculated for central events at
mid-rapidity, averaged over experimental
acceptance in pt.With the assumption of equal
acceptance of particle and antiparticle no
corrections have to be applied
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Energy Evolution of B/B Ratio
Production of baryons through pair processes
increases dramati-cally with ?s still not
baryon free
STAR preliminary
Pair-process production is larger than baryon
transport
(ISR)
Note 2/3 of protons from pair processes, yet pt
dist. the same as antiprotons
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Statistical models

• Braun-Munzinger et al. (hep-ph/0106066)
• - Follows curve for ltEgt/ltNgt 1 GeV at
  freezeout
• - Usesphenomenologicalparameterization

J. Cleymans K. Redlich,PRL 81 (1998) 5284
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T and mB according to thermal model
Assumption strangeness in complete equilibrium
i.e. strangeness saturation factor gs 1
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Strangeness production
Lines of constant lS where
ltEgt/ltNgt 1 GeV
Braun-Munzinger et al.hep-ph/0106066
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Wroblewski factor evolution
dependent on T and mB dominated by Kaons
Wroblewski factor
PBM et al., hep-ph/0106066
total
mesons
baryons
hidden strangeness mesons
Peaks at 30 A GeV in AA collisions due to strong
mB dependence
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Statistical model fit at 130 GeV
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Chemical fit result
Central
K/K-
Chemical freeze-out parameters Tch 1794
MeV mB 514 MeV ms -0.82.0 MeV gs 0.99
0.03 c2/dof 1.5
BRAHMS PHENIX PHOBOS STAR
X/X-
p-/p
p/p
L/L
K/p
K-/p-
K/h-
p/p
Ratio (chemical fit)
K-/h-
p/p-
K0s/h-
K0/h-
L/h-
L/h-
f/h-
X-/h-
X/h-
Model M.Kaneta, Thermal Fest (BNL, Jul 2001),
N.Xu and M.Kaneta, nucl-ex/0104021
Ratio (data)
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K/p ratio as a function of beam energy
saturation ?
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K/p ratio as a function of beam energy
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Experimental L/p
4p yields
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Strange Baryon production as a f(centrality)
Note spectra are not feed-down corrected
L yields are from fits to Boltzmann h- yields
are power law fits
Saturation ?
ConclusionStrange baryon over charged particle
ratio is constant
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Implications for ratios
Statistical errors only Mid-rapidity ratios
(0.2)
Braun-Munzinger et al.hep-ph/0106066
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Implications for ratios
Statistical errors only Mid-rapidity ratios
(0.2)
(PRELIMINARY)STAR 130 GeV14 central
(L/p????????
Braun-Munzinger et al.hep-ph/0106066
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Sensitivity to multi-strange baryons
Stat. model cant get a ??/p? ratio above 0.09 in
this phase space!
D. Magestro private communication
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Sensitivity to multi-strange baryons
X/p?
Braun-Munzinger et al.hep-ph/0105229 Thermal
fit resultsin T 174 MeV, mB 46 MeV. Grand
canonicalensemble, unlikeprevious model
Statistical errors only
(Preliminary) STAR 130 GeV14 central data
Ratios
Model gets K-/p?,L/p- correct, butmisses on X
ratios!!!
T (MeV)
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Quark-Counting Ratios (ALCOR model)
Biro, Levai, Zimanyi Phys. Lett. B347 (1995) p6
Assumption formation of a constituent quark
plasma with subsequent coalesence of the quarks
into hadrons
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Quark-Counting Ratios from STAR data
Measured
Predicted
Quark-counting ratios are consistent with each
other
Will change slightly with feeddown corrections
(not included here)
STAR Preliminary
Statistical errors only
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Quark coalescence for mixed ratios
As mB -gt 0, sensitivity of the model to
particle/antiparticle ratios is lost. Must look
at ratios of dissimilar species to resolve model
accuracy.
130 GeV
X-/p?
Quark coalescence (ALCOR)
Quark coalescence does better with X????
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L/p ratio correction factors

• Lm LS0XW
• LS0??????????? Lm
• pm p(0.64Lm0.52S)
• p 0.88 (LS0?? 0.52S p1.01 (LS0??
• pm/Lm 0.74 0.73 p/(LS0??
• p/(LS0?? 1.?? pm/Lm 1.01

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Sudden hadronization model (1999)
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Sudden hadronization model (2001)
J. Rafelski inhep-ph/0111467
Large ratio at AGS (and SPS) still not understood
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Stat. model 200 GeV predictions
Use parameterization
(CAUTION! Really for 4p ratios)
Becattini et al.PRC 64 (2001) 024901
Statistical errors only
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Stat. Model Predictions Revisited
Use parameterization
(Preliminary)STAR 130 GeV Data
(CAUTION! Really for 4p ratios)
Becattini et al.PRC 64 (2001) 024901
Statistical errors only
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What about other models ?
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Some Conclusions