Charged Hadron Results from 19'6 GeV Au Au

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Charged Hadron Results from 19.6 GeV AuAu
Daniel Cebra University of California, Davis (for
the STAR Collaboration)
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Triggering for the 19.6 GeV dataset
The STAR trigger was not optimized for 19.6 GeV
Collisions. The correlation between ZDC and CTB
that had been observed in the 130 and 200 GeV
data sets was not seen in the lower energy
collisions. To approximate a minimum bias
trigger, events were selected if they satisfied
either a minimum ZDC threshold or a minimum CTB
threshold. Triggering will be a resolvable issue
for the future beam energy scan.
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The STAR 19.6 GeV AuAu Data Set

• One day of running
• 12 data runs
• Total recorded events 175466
• Events with good vertex 42412
• 10 centrality events 5106

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Centrality Determination
The mid-y (hlt0.5) charged particle multiplicity
is shown on the left for the four RHIC collision
energies. The cut lines correspond to percentages
of the total minimum bias cross section. Note
the 20 GeV trigger had inefficiencies for
collisions in the impact parameter range
corresponding to 10-30 and 70-100 Using a
Glauber Model, we estimate that our 0-10 data
selection had an average number of participant
sof 337.
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Spectra as a Function of Centrality
200 GeV AuAu and pp data STAR PRL92, 112301 (2003)
STAR PRELIMINARY
Identified Hadron spectra at mid-rapidity are
displayed for several centrality selctions.
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Charged Particle Spectra Compared SPS
The central mid-rapidity spectra are displayed
against the most comparable SPS spectra
STAR PRELIMINARY
NA44 PRC66, 044907 (2002) - all NA49 PRC66,
054902 (2002) - pim, kam, and kap NA49 PRC69,
024902 (2004) - protons NA49 nucl-ex/0512033 -
protons and anti-protons WA98 PRL83, 926 (1999)
- pi-zero WA98 NPA698, 647 (2002) - pim WA98
PRC67, 014906 (2003) - pim and kam
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Correcting the Comparisons
Energy Dependence
Centrality (Np) Effect
Studied the rapidity densities, then determine
the effect of the rapidity slice for each particle
NA49 rapidity density data N(A661, 45c (1999)
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Comparisons of Pion Yields
Fit all experimental data with exponential over
the range 200-800 MeV/c2
Fix temperature to 185 and corre t for difernces
in centrality, rapidity, and beam eanergy
STAR PRELIMINARY
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Kaon Yields
Fit all experimental data with exponential over
the range 100-600 MeV/C2
STAR PRELIMINARY
Fix temperature to 250 and corre t for difernces
in centrality, rapidity, and beam eanergy
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Proton Yields Corrected for Feed-down
Fit all experimental data with exponential over
the range 200-800 MeV/c2
Fix temperature to 300 and corre t for difernces
in centrality, rapidity, and beam eanergy
STAR PRELIMINARY
STAR Data are corrected using NA49 Lambda and
anti-Lambda results
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Fitting the Shape of the Spectra
In order to estimate the integrated yield, the
spectral shapes are modeled and extrapolated
STAR PRELIMINARY
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Radial Flow Analysis
200 GeV data STAR PRL92, 112301 (2003)
STAR PRELIMINARY
FoPi NPA612, 493 (1997) FoPi NPA610, 49c
(1996) EOS PRL75, 2662 (1995) E866 APPB29, 3253
(1998) NA44 PRL78, 2080 (1997) NA49 PRL82, 2471
(1999) PHENIX NPA715, 498 (2003) BRAHMS
nucl-ex/0404011 STAR PRL92, 112301 (2003)
Statistical Model Tch 164.7 /- 0.5 mB
205.5 /- 0.6 mS 27.2 /- 0.9
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Rapidity Density Distributions
NA44 PRC66, 044907 (2002) - all NA49 PRC66,
054902 (2002) - pim, kam, and kap NA49 PRC69,
024902 (2004) - protons NA49 nucl-ex/0512033 -
protons and anti-protons WA98 PRL83, 926 (1999)
- pi-zero WA98 NPA698, 647 (2002) - pim WA98
PRC67, 014906 (2003) - pim and kam
The yields are studied as a function of rapidity
and centrality
STAR PRELIMINARY
STAR PRELIMINARY
STAR PRELIMINARY
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Particle Ratios
STAR PRELIMINARY
E802 NPA610, 139c (1996) E802 PRL81, 2650
(1998) E866 PLB476, 1 (2000) E917 PLB490, 53
(2000) NA49 PRC66, 054902 (2002) NA44 PRC66,
044907 (2002) PHENIX PRC69, 034909 (2004) STAR
PRL92, 112301 (2003) STAR PLB595, 143 (2004) STAR
PRL86, 4778 (2001) STAR PLB567, 167 (2003)
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K/p Ratios
STAR PRELIMINARY
E802 PRL81, 2650 (1998) E866 PLB476, 1
(2000) E917 PLB490, 53 (2000) NA44 PLB471, 6
(1999) WA98 PRC67, 104906 (2003) NA49 PRC66,
054902 (2002) NA49 EPJC33, S621 (2004) NA49
arXiv0710.0118v2 PHENIX PRC69, 034909
(2004) PHENIX PRL88, 242301 (2002) STAR PRL92,
112301 (2003) STAR PLB595, 143 (2004)
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Pion Ratios
The pion ratios are fit with a coulomb model. The
extracted potential of the source is 8.5 MeV
STAR PRELIMINARY
KaoS PLB420, 20 (1998) E866 NPA610, 139c
(1996) NA44 PLB372, 339 (1996) WA98
nucl-ex/0607018 STAR PRL92, 112301 (2003)
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Standard ? HBT analysis

• impressive agreement STAR AuAu _at_19.6GeV with
  CERES/NA49 PbPb _at_17.3 GeV
• weak ?s dependence of HBT cancels weak Abeam
  dependence --gt applesapples
• Scale and p-dep. of homogeneity regions
• follow already-established trends
• disfavor signals of increased lifetimes at
  intermediate collision energies

Slide courtesy of Z. Chajecki and M. Lisa
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Summary

• We have measured the pion, kaon, and proton
  spectra in 19.6 GeV AuAu collisions
• These spectra have been measured as a function
  of rapidity and centrality
• Detailed comparisons of these spectra to the
  published SPS results have been made, in most
  cases the results are compatible.
• The RHIC Beam Energy Scan will be able to reduce
  the statistical and systematic errors.

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Backup Slides
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STAR PRELIMINARY
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2001 19.6 GeV AuAu collisions

• 2 days of 9.8 GeV beams
• 0.4 mb-1 integrated luminosity
• ?3m by necessity
• 60-90 minute stores
• 56 Au bunches, 0.6x109/bunch
• 10-30 Hz ZDC rates
• IBS and aperture dominated beam and luminosity
  lifetime
• Another run at this energy may improve this by
  factor of 2-5
• 1.0x109/bunch
• Raise ? to improve lifetime
• RHIC is best used as a storage ring collider
  below beam energies of 12 GeV

STAR PHENIX
Figure from T. Satogata
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Added 62.5
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Studied the production trends as a function of Np
and root S
Parameterized the energy dependence
Flat as a function of Np for central collisions
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STAR PRELIMINARY
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p-
STAR NA49 WA98 NA44
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p
STAR WA98 NA44
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K-
STAR NA49 WA98 NA44
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K
STAR NA49 NA44
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p-
STAR NA49 NA44
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p
STAR NA49 NA44
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Proton Yields before correction
Fit all experimental data with exponential over
the range 200-800 MeV/c2
Fix temperature to 300 and corre t for difernces
in centrality, rapidity, and beam eanergy
STAR PRELIMINARY
Corrected for hyperon feeddown
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STAR 62.5 2.72 /- 0.24 200 3.94 /- 0.28
STAR PRELIMINARY
PRC 71, 0344908 (2005)

• PHENIX
• 19.6 1.86 /- 0.15
• 3.46 /- 0.18
• 200 3.89 /- 0.23

NA49 17.2 1.86 /- 0.08 12.4 1.54 /-
0.07 8.7 1.24 /- 0.06
NA45 17.2 1.87 /- 0.19 8.7
1.35 /- 0.08 NA50 17.2 1.98 /- 0.16
8.7 0.95 /- 0.10
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NA44
STAR PRELIMINARY
NA49