Results on Particle Yields from the PHENIX Experiment at RHIC

1
Results on Particle Yields from the PHENIX
Experiment at RHIC
Tatsuya Chujo (BNL) for the PHENIX Collaboration
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Space-time Evolution of System at RHIC
Hadronization (Freeze-out)
Expansion
Mixed phase
QGP phase
Thermalization
Pre-equilibrium
Hadrons reflect the bulk property of created
system and its evolution!
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Characterize freeze-out

• Hydrodynamic Collective Expansion
• Identified charged hadron spectra vs. centrality
• ltpTgt vs. centrality
• Hydro-dynamical model fit.
• Elliptic flow (identified particle) vs. hydro.
  model
• Space-time evolution of the System
• Pion HBT correlation (kT and centrality
  dependence)
• Deuteron / anti-deuteron spectra and coalescence
  model
• Chemical Composition
• Particle ratios for same mass
• p/ p ratio vs. pT and centrality
• dN/dy for p, K, p and anti-proton vs. centrality
• L, Lbar yield

We present the first results of identified
charged hadrons in AuAu _at_ sqrt(sNN) 200 GeV
at mid-rapidity from the PHENIX experiment.
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Event Selection

• Centrality selection Used charge sum of
  Beam-Beam Counter (BBC, h 34) and energy of
  Zero-degree calorimeter (ZDC) in minimum bias
  events.
• Extracted Npart based on Glauber model.

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Charged Particle Identification at PHENIX

• Single particle spectra and
• elliptic flow w.r.t reaction
• plane analysis
• PID by high resolution TOF
• broad pT range
• p, K lt 2 GeV
• proton, anti-proton lt 4 GeV
• Df p/4

• HBT analysis
• Time-of-Flight
• by Calorimeter
• large acceptance
• (Df p)

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Single Particle Spectra at most central events
(0-5 )
PHENIX Preliminary
PHENIX Preliminary
AuAu at sqrt(sNN) 200GeV
AuAu at sqrt(sNN) 200GeV

• proton yield pion yield _at_ 2 GeV

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Pion pT spectra (centrality dependence)
p
p-
PHENIX Preliminary
PHENIX Preliminary
Characterized by power law shape for all
centralities
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Kaon pT spectra
K
K-
PHENIX Preliminary
PHENIX Preliminary
Characterized by mT exponential shape for all
centralities
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p, pbar pT spectra
p
PHENIX Preliminary
PHENIX Preliminary
Characterized by Boltzmann function shape for all
centralities
10

• One way to characterize expansion is ltpTgt vs.
  centrality.

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ltpTgt vs. Npart
ltpTgt GeV/c
ltpTgt GeV/c

• Systematic error on
• 200 GeV data
• p (10 ), K (15 ),
• p (14 )

open symbol 130 GeV data

• Increase of ltpTgt as a function of Npart and
  tends to saturate
• p lt K lt proton (pbar)
• Consistent with hydrodynamic expansion picture.

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Hydrodynamic Model Fit to the Spectra
See talk of J.M. Burward-Hoy
Most central collisions for 200 GeV data
Freeze-out Temperature Tfo 110 ? 23
MeV Transverse flow velocity bT 0.7 ? 0.2
Ref E. Schnedermann, J. Sollfrank, and U.
Heinz, Phys. Rev. C 48, 2462 (1993)

• bT increases from peripheral to mid-central
  (Npart lt 150) and
• tends to saturate for central collisions.

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• The elliptic flow (azimuthal asymmetries)
  provides information on pressure at very early
  stage of the collisions.

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Elliptic Flow Measurements w.r.t reaction
Target
Projectile
Au
Reaction plane determination By Beam-beam counter
(h34) Less non-flow contributions.
Au
Reaction plane
b Impact parameter
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v2 of Identified Hadrons
See talk of S. Esumi
AuAu at sqrt(sNN) 200GeV, Minimum bias,
Reaction Plane h 34
v2
v2
hydro model including the1st order phase
transition with Tf120MeV () pion
proton
P. Huovinen et al. Phys. Lett. B503 (2001)
58
Negatives p-K-, pbar
Positives p K, p
PHENIX Preliminary
PHENIX Preliminary
PHENIX Preliminary
PHENIX Preliminary
pT (GeV/c)
pT (GeV/c)

• Good agreement with hydrodynamic model
  calculation up to 1.5 GeV.
• Deviation for pions from model at higher pT?

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• Another experimental constraint on expansion
• HBT vs. momentum

Bertsch-Pratt parameterization
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kT dependence of R
Centrality is in top 30

• Broad ltkTgt range 0.2 - 1.2 GeV/c
• All R parameters decrease as a function of kT
• ? consistent with collective
  expansion picture.
• Stronger kT dependent in Rlong have been
  observed.

kT average momentum of pair
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R vs. Npart1/3
AuAu at sqrt(sNN) 200GeV
Fit with p0p1Npart1/3 Rout weaker increase
with Npart
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Rout/ Rside vs. kT and Npart

• No dependence of Rout/Rside as a function of
  ltkTgt and Npart
• Large kT range is strong challenge for dynamical
  models.

See talk of A. Enokizono (3D pp, KK) and poster
of M. Heffner (1D KK, pp)
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• Deuteron Coalescence from proton and neutron
  provides another measure of space-time evolution
  to be compared to HBT.

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Deuteron Identification by TOF
AuAu at sqrt(sNN) 200GeV

• Clear deuteron and anti-deuteron signals have
  been observed
• in 200 GeV data, using 23 M minimum bias
  events.

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Deuteron and anti-deuteron spectrum
AuAu at sqrt(sNN) 200GeV

• PID by TOF detector.
• Fitted by mT exponential function.

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Coalescence model for anti-deuteron
See poster of A.K. Purwar and R. Rietz
1/B2 QV
AuAu at sqrt(sNN) 200GeV

• Weak beam energy dependence from SPS to RHIC.
• Similar behavior has been observed in pion HBT
  correlations.

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• Chemical composition at freeze-out can be deduced
  from particle ratios.

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p-/ p ratio vs. pT
Central
Peripheral
AuAu at sqrt(sNN) 200GeV
AuAu at sqrt(sNN) 200GeV
p-p data (200 GeV)

• Flat pT dependence
• No centrality dependence

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K-/K
Central
Peripheral
AuAu at sqrt(sNN) 200GeV
AuAu at sqrt(sNN) 200GeV
p-p data (200 GeV)

• Flat pT dependence
• No centrality dependence

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pbar/p
Central
Peripheral
AuAu at sqrt(sNN) 200GeV
AuAu at sqrt(sNN) 200GeV

• Flat pT dependence for central.
• Decreasing for peripheral gt 3 GeV?

See talk of T. Sakaguchi (Au-Au) and poster of
S. Sato (p-p data)
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pbar/p in proton-proton
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Estimate of Baryon Potential
Statistical thermal model
hep-ph/0002267 F.Becattini et al.
PHENIX preliminary (200 GeV), central (0-10)

• p- / p 1.02 ? 0.02 (stat) ? 0.1 (sys)
• K- / K 0.92 ? 0.03 (stat) ? 0.1(sys)
• pbar / p 0.70 ? 0.04 (stat) ? 0.1(sys)

Baryon chemical potential mB 30MeV
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p /p
See talk of T. Sakaguchi
p /p
Central
Peripheral

• proton yield is comparable with pions _at_ 2 GeV in
  central collisions, less in peripheral.

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dN/dy
PHENIX Preliminary
PHENIX Preliminary
AuAu at sqrt(sNN) 200GeV
AuAu at sqrt(sNN) 200GeV
p
p
dN/dy / (0.5 Npart)
K
K-
p
open symbol 130 GeV data
pbar
Positive
Negative
Npart
Npart

• Similar centrality dependence 130 GeV and 200 GeV

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Ls via combinatorial method
AuAu at sqrt(sNN) 130GeV
nucl-ex/0204007
Invariant mass distribution
Well described by Boltzmann function (0.4 lt pT lt
1.8 GeV/c) for central 0-5 and minimum bias
spectra.
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Feed-down corrected p, pbar spectra
See poster of T. Arkadij

• Ratios (130 GeV data)

nucl-ex/0204007
L/p 0.89 ?
0.07(stat) (anti-L)/(anti-proton) 0.95 ?
0.09(stat) (anti-L)/L 0.75
? 0.09(stat)
AuAu at sqrt(sNN) 130GeV
nucl-ex/0204007

• Reasonable agreement in net L and proton yield
  by HIJING/B model
• (non perturbative gluon junction mechanism)

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Summary (I)

• We presented the first results of
  identified charged particle spectra and yields
  (p, K, p, pbar, d, dbar), azimuthal correlation
  w.r.t reaction plane for identified hadrons, HBT
  correlations at sqrt(sNN) 200 GeV and the L
  results from 130 GeV data.
• Hydrodynamic Collective Expansion
• All results of 200 GeV data indicate a strong
  collective expansion at central collisions.
• ltpTgt vs. centrality the heavier mass, the
  larger ltpTgt, steep rise at peripheral to
  mid-central collisions.
• Hydro-dynamical model fit to the spectra ? bT
  0.7, Tfo 110 MeV
• Elliptic flow (identified particle) vs. hydro.
  Model
• ? Good agreement with hydro model lt 1.5 GeV,
  deviated from hydro
• gt 2GeV for pions.

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Summary (II)

• Space-time evolution of the System
• R values are very similar to sqrt(sNN) 130 GeV.
  
• Much large kT range for HBT in 200 GeV data.
• No dependence of Rout/Rside on ltkTgt, Npart.
• Deuteron, anti-deuteron B2 show weak energy
  dependence from SPS to RHIC, similar to HBT
  results.
• Chemical Composition
• Baryon chemical potential 30 MeV.
• No pT and centrality dependence for p- /p,
  K-/K, pbar/p ratio.
• proton yield is comparable with pions _at_ 2 GeV in
  central collisions, less in peripheral.
• Feed down corrected p, pbar spectra for 200 GeV
  data
• can be done soon.

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dNch /dy comparison
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130 GeV vs. 200 GeV (MB)
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Single Particle Spectra at most peripheral
events (80-91 )
AuAu at sqrt(sNN) 200GeV
AuAu at sqrt(sNN) 200GeV
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Comparison between 130 GeV and 200 GeV

• Less protons in 200 GeV data than 130 GeV data

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K/p Ratio vs. pT

• K/p ratio above 1.5 GeV (peripheral) lt
  (mid-central) lt (central)
• ? reflected shape changes as a function
  centrality

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Two Particle Correlations (HBT) for pions

• Full analytic coulomb corrections.
• Taking account two track separations.
• 50 M Minimum-bias data sample.

Bertsch-Pratt parameterization
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3D HBT Example for pions
PHENIX Preliminary
AuAu at sqrt(sNN) 200GeV
50 M M.B. events
0.2ltkTlt2.0GeV/c, ltkTgt0.46GeV/c
Bertsch-Pratt parameterization
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L Analysis (130 GeV data)
PbSc

• Used 1.3 M minimum bias events from 130 GeV
  data.
• Hadron PID by EMC (PbSc)
• West arm PbSc EMC-TOF (sTOF 700 ps in Run1) for
  PID (2s cut)
• Pion ID pT lt 0.6 GeV/c, proton ID pT lt 1.4
  GeV/c
• Used combinatorial method to extract lambda.

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L/L ratio vs. pT and Npart

• No pT and Npart dependences in
• anti-L/L ratio
• Averaged anti-L/L ratio
• 0.75 ? 0.09
• No pT dependence ?
• Consistent with the statistical
• thermal model

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PID plot for reaction plane v2 analysis
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v2 of Identified Hadrons (p, K, p)
AuAu at sqrt(sNN) 200GeV, Minimum bias,
Reaction Plane h 34
v2
v2
PHENIX Preliminary
PHENIX Preliminary

• Hydro model P. Huovinen et al.
• Phys. Lett. B503 (2001) 58

Negatives h-,pi-,K-,pbar
Positives h,pi,K,p
PHENIX Preliminary
PHENIX Preliminary
pT (GeV/c)
pT (GeV/c)
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