Scaling Properties of Identified Hadron
Transverse Momentum Spectrain Au+Au and Cu+Cu Collisions at RHIC-PHENIX
Masahiro Konno
for the PHENIX Collaboration(University of Tsukuba)1
JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)Hadron production in heavy ion collisions at RHIC
- Hadron production mechanisms:
Thermal emission
Quark recombination
Jet fragmentation- Bulk properties of the system:
Thermalization
Soft Collective flow
Freeze-out (Chemical, Kinetic)- High-pT phenomena in the medium:
Hard Jet quenching(Energy loss)
Particle correlation of jets

Space-time evolutionof a heavy ion collision- Single particle spectra and particle ratios provide the most basic observables
to investigate the mechanisms of hadron production.
- Particle Identification (PID) over wide pT range is also crucial.
JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)

2

Hadron production at intermediate pT- Baryon/meson difference at intermediate pT (2~5 GeV/c)
Baryon enhancement in particle ratios
Splitting of v2 strength into baryon/meson groups- Now explained in quark recombination picture- A transition from soft to hard production at intermediate pTp/πp/πWhat is the next?
Purposes:- Relative contributions ofhadron production mechanisms (soft/hard)- Scaling properties of identified hadronpT spectra in different collision systems.

nucl-ex/0608033- Systematic scan over different collisionsystems (colliding species, beam energies)
with available data obtained at PHENIX.

v2
PHENIX
preliminary(Au+Au, Cu+Cu at 䌥sNN = 62.4, 200 GeV)3

JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro
Konno (Univ. of Tsukuba)(=mT-m)PHENIX Detector

EM Calorimeter (PID)
TOF(PID)- Central Arm Detectors- Centrality and Reaction Plane-determined on an E-by-E basis.
- PID (particle identification) isa powerful tool to study hadronproduction.

Aerogel Cherenkov (PID)
Aerogel Cherenkov (ACC)p (p) ID up to 7 GeV/cp

Time of Flight (TOF)-p (p) ID up to 4 GeV/c

Drift Chamber(momentum meas.)

K+Tracking detectors(PC1,PC2,PC3)

π+4JPS 2007
Spring, 3/26/2007,TMU, Tokyo
Vetofor protonID

Masahiro Konno (Univ. of Tsukuba)

Blast-wave Model Fit* Ref: PRC48(1993)2462- Blast-wave model is a hydrodynamic-inspired model.
- Extracting kinetic freeze-out properties with BW model.
- Simultaneous fit to pT spectra (π/K/p) for each centrality class.
χ2 map(* Resonance decay feed-down correction not applied.
Instead, tighter pT fitting range used.
π; 0.6-1.2 GeV/c K; 0.4-1.4 GeV/c, p/pbar; 0.6-1.7 GeV/c)

JPS 2007 Spring, 3/26/2007, TMU, TokyoSpectra for heavier particles
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has a convex shape due to radial flow.

Masahiro Konno (Univ. of Tsukuba)

Blast-wave Model Fit - Tfo vs. Npart

Tfo ~120 MeV- Npart scaling of Tfo between Au+Au and Cu+Cu- Almost same Tfo at 䌥sNN = 62.4, 200 GeV
6JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)

Blast-wave Model Fit - <βT> vs. Npart<βT> ~0.5- Npart scaling of <βT> between Au+Au and Cu+Cu- Almost same <βT> at 䌥sNN = 62.4, 200 GeV
7JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)<pT> vs. Npart
䌥sNN = 200 GeV

䌥sNN = 62.4 GeVp(pbar)

Kπ- <pT>: π<K<p (mass dependence)- Consistent with radial flow picture- Npart scaling of <pT> between Au+Au and Cu+Cu- Almost same <pT> at 䌥sNN = 62.4, 200 GeV
8JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)

Estimation of p/π at intermediate pT- Extrapolate low-pT Blast-wave fit results
to intermediate pT in order to estimate p/π ratio.

(hydro p)/(hydro π)(hydro p)/(real π)

Central* No weak decay feed-down
correction applied.

Peripheral- Hydrodynamic contribution for protons is oneof the explanations of baryon enhancement.
- Other contribution is also needed: Recombination, Jet fragmentation
9JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)Baryon enhancement - p/π vs. Npart

Phenix preliminary

Au+Au vs. Cu+Cu at 200 GeV

Au+Au vs. Cu+Cu at 62.4 GeV- Npart scaling of p/π between Au+Au and Cu+Cu at same 䌥sNN
10JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)Baryon enhancement - p/π vs. dET/dyPhenix preliminary

Phenix preliminary- No Npart scaling of p/π (pbar/π) in Au+Au between 62.4 and 200 GeV.
- dET/dy scaling of pbar/π seen. => Proton production (at this pT range)
at 62.4 GeV is partly from baryon transport, not only pair production.
Nuclear stopping is still large at 62.4 GeV.
11JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)

Statistical Model Fit - µq vs. Npartµq ~8 MeV- Npart scaling of µq between Au+Au and Cu+Cu- Larger µq at 䌥sNN = 62.4 GeV than that at 200 GeV
12JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)Summary- Scaling properties of PID pT spectra tested
with Au+Au and Cu+Cu data at 䌥sNN = 62.4/200 GeV.
- Bulk properties (dN/dy, <pT>, kinetic and chemical freeze-outproperties) are scaled with Npart (~volume) at same 䌥sNN.
- p(pbar)/π ratios:(1) Npart scaling between Au+Au and Cu+Cu at same sqrt(sNN)(2) dET/dy scaling between 62.4 and 200 GeV in Au+Au(3) pbar/π is a good indicator of baryon enhancement

On-going- MRPC-type TOF counter (σTOF~100ps) wasinstalled behind the Aerogel for high-pT PIDupgrade. Run-7 has just started for 200 GeV
Au+Au. Higher-pT physics can be reached.
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JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)

Backup
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JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)

Statistical Model Fit- Extracting chemical freeze-out properties with statistical model fit.
- Fitting particle ratios of dN/dy (π/K/p) at y~0.
- Assuming chemical equilibrium of light quarks (u,d,s), γs=1.
- Partial feed-down correction taken into account.
Refs:
Phys. Rev. C71 054901, 2005
nucl-th/0405068
NPA698(2002)306C- Tch, µq : relatively stable- µs, γs : not determined with this set of ratios (π/K/p). Strangeness info is short.

䌥sNN = 200 GeV
JPS 2007 Spring, 3/26/2007, TMU, Tokyo

䌥sNN = 62.4 GeV

Masahiro Konno (Univ. of Tsukuba)

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Statistical Model Fit - Tch vs. Npart

Tch ~160 MeV

If γs is free,
Tch = 155 +/- 7 MeV- Npart scaling of Tch between Au+Au and Cu+Cu- Almost same Tch at 䌥sNN = 62.4, 200 GeV
16JPS 2007 Spring, 3/26/2007, TMU, Tokyo

Masahiro Konno (Univ. of Tsukuba)