Systematic Study of Identified
Particle Production in PHENIX
Masahiro Konno
Univ. of Tsukuba, for the PHENIX Collaboration

1QM2005 Budapest, Hungary

Outline- Physics Motivation- Method- New Data Set: Cu+Cu 200GeV- Results and Comparisons:- Baryon Enhancement- Energy dependence- Npart Scaling (Particle Ratio)- Npart Scaling (RAA)- Summary

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Physics Motivation

PHENIX: PRL 91, 172301 (2003), PRC 69, 034909 (2004)- Strong suppression of !0 yields above pT~2 GeV/c at RHIC, but no suppression forproton and antiproton at intermediate pT(2-5 GeV/c): “Baryon Anomaly at RHIC”.
- The possible explanations:
Quark recombination,Baryon junction, Strong radial flow …

For Systematic Study:- Energy dependence
62.4 GeV vs. 200 GeV (Au+Au)- System Size dependence
Cu+Cu vs. Au+Au (200 GeV)
3QM2005 Budapest, Hungary

Method: Charged Hadron PID
Time of Flight

Aerogel Cherenkov("=120ps)(n=1.011)

TOF

Aerogel
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4New Data Set: Cu+Cu 200 GeV

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pT Spectra

Cu+Cu 200 GeV

Similar shapes as those in Au+Au.

NOTE: No weak decay feed-down correction applied.
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Cu+Cu 200 GeV-/+ Ratios vs. pT!-/!+K-/K+pbar/p- Flat pT dependence for pions, kaons.
- Slightly decreasing with pT for protons.
- Flat centrality dependence also seen (0-60%).
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K/! vs. pTCu+Cu 200 GeV- Increasing steady with pT.
- No apparent indication ofsaturation in this pT region.
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8Baryon Enhancement

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p/!+ vs. pT
Au+Au 200GeV

Au+Au 62GeV

Cu+Cu 200GeV- Baryon enhancement observed in all collisions systems.
- Rapidly increasing with pT for 62 GeV.
- pT dependence in Cu+Cu is similar to that in Au+Au. (See Npart-scaling)- Weaker centrality dependences (62GeV) than those of 200 GeV.
NOTE: No weak decay feed-down correction applied.
QM2005 Budapest, Hungary

10pbar/!- Ratios
Au+Au 200GeV

Au+Au 62GeV

Cu+Cu 200GeV- Less for antiproton compared to proton for all systems- Significant difference for p and pbar at 62 GeV(Indicating more baryon transport and less p-pbar pair production at 62 GeV than 200 GeV.)
NOTE: No weak decay feed-down correction applied.
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Au+Au 62GeVp/! Ratios(62 GeV)nucl-th/0412043- Described by coalescence model:- pT dependence- p and pbar difference

coalescence model
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12Energy dependence

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Antibaryon/ baryon ratios vs. $sNNpbar/p (PHENIX)@ 62.4 GeV

Experimental Data:AGS:• E802, 2650 PRL 83, (1998)
SPS:• NA44: PRC 66, 044907 (2002)• NA49: J. of Phys. G 30, S357 (2004)
RHIC:• PHENIX
62 GeV (preliminary, no feed-down)
PRL 88, 242301 (2002), PRC 69, 034909(2003), PRL 89 092302 (2002).
• STAR
62 GeV (Preliminary, HQ2004); 130 GeV
PRL 89, 092301 (2002).

- Follow the smooth curve from SPS to RHIC.
- Consistent with #bar/# (STAR preliminary) at 62 GeV.
NOTE: No weak decay feed-down correction applied.
QM2005 Budapest, Hungary

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dN/dy vs. $sNN (central)

PHENIX Preliminary
62 GeV (0-10%)

RHIC: PHENIX
SPS: NA44, NA49
AGS: E866, E917

dN/dy per Npart pair: smooth energy dependence from SPS to RHIC.
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K/! vs. $sNN

PHENIX Preliminary
62 GeV (0-10%)* STAR K+/!+: preliminary
data from SQM04, J. Takahashi- K-/!- : follow the smooth curve from SPS to RHIC.
- K+/!+: similar to SPS top energy.
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Npart Scaling (Particle Ratio)

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K/! vs. NpartNpart dependence is almost same as in Au+Au.
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p/! vs. Npart- Npart dependence looks similar to that in Au+Au.
- Slight difference in the magnitude seen.
NOTE: No weak decay feed-down correction applied.
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Npart Scaling (RAA)20
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RAA vs. Npart!0

Cu+Cu data follow the Au+Au data.
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RAA vs. pT

Npart~98

Npart~114

Cu+Cu 200 GeV
Central (0-10%)

Au+Au 200 GeV
Mid-Central (30-40%)- Similarity seen in Cu+Cu and Au+Au:- The magnitude of enhancement/suppression- Particle type dependence
NOTE: No weak decay feed-down correction applied.
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SummaryEnergy dependence:
62.4 GeV vs. 200 GeV (Au+Au)- Observed a large proton contribution at intermediate pT,
as seen in 200 GeV data, but less for antiprotons.
- Antiproton-to-proton ratio is ~0.5 at 62 GeV,
which indicates less p-pbar pair production
and relatively larger baryon transport than 200 GeV.
- Smooth excitation function for both yields and ratiosfrom SPS to RHIC.

System Size dependence:
Cu+Cu vs. Au+Au (200 GeV)
- Observed a large p,pbar contribution at intermediate pT,
as seen in 200 GeV data.
- Npart dependences on particle ratios have similar trend
as in Au+Au (Npart scaling).
- Similarity on RAA seen in Cu+Cu and Au+Au (System size):- the magnitude and its particle dependence.
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Backup

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Inverse Slope TCu+Cu 200 GeV

Fitted by mT exponentialfunction.
- Fit range:• !: 0.3(0.2) - 1.0 GeV/c2.
• p and K: 0.2(0.1) - 1.0 GeV/c2.
• Extracted inverse slopes

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Au+Au 200 GeV

Lambda RCP
Run2

Run4

Rcp of Lambdas is similar to protons
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pT Spectra

Au+Au 62 GeV

0-10%

10-30%

30-60%
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-/+ Ratios

Au+Au 62 GeV

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-/+ Ratios (Centrality dep.)
Au+Au 62 GeV

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