Flow Measurement in PHENIX

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Flow Measurement in PHENIX
Masahiro Konno (Univ. of Tsukuba) for the PHENIX
Collaboration
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Outline

• Physics Motivation
• Method, PHENIX detector
• Single Particle Spectra
• - p/? ratios
• - Npart Scaling of p/? in AuAu, CuCu
• - RAA in AuAu, CuCu
• Elliptic Flow
• - Scaling properties of v2
• Summary

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Single Particle Spectra
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Physics Motivation
- Baryon Enhancement -
RAA
AuAu 200 GeV

• High-pT suppression due to parton energy loss
• in the medium (jet quenching).
• The suppression patterns depend on particle
  type.
• Protons are enhanced, while pions and kaons are
  suppressed.

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PHENIX detector
EM Calorimeter (PID)
TOF (PID)

• - Central Arm Detectors
• Centrality and Reaction Plane
• determined on an E-by-E basis.
• PID (particle identification) is
• a powerful tool to study hadron
• production.

Aerogel Cherenkov (PID)
Aerogel Cherenkov (ACC)
Time of Flight (TOF)
Drift Chamber (momentum meas.)
p
K
Tracking detectors (PC1,PC2,PC3)
p
Veto for proton ID
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pT spectra (CuCu vsNN 200 GeV)
(Anti-) protons
ACC

• - CuCu is a smaller system compared to AuAu.
• pT reach extended for (anti-)protons with fine
  centrality bins.
• lt (1) Aerogel Cherenkov, (2) Enough statistics
  in AuAu/CuCu

NOTE No weak decay feed-down correction applied.
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pT spectra (pp vs 200 GeV)

• High statistics 200 GeV pp data.
• More than10 times statistics used compared to
  previous Run3 pp analysis.
• The pp data provides baseline spectra to heavy
  ion data, and it is
• important to quantify in-medium nuclear effects
  in heavy ion collisions at RHIC.

NOTE No weak decay feed-down correction applied.
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p/? vs. pT
AuAu 200 GeV
ACC
p/?
- p/? (pbar/?) ratios seem to turn over at
intermediate pT, and be close to the value of
fragmentation at higher pT. - Clear peak in
central events than that in peripheral. -
Indicating a transition from soft to hard at
intermediate pT.
NOTE - No weak decay feed-down correction
applied. - pp data (PRC 74, 024904
(2006))
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p/? vs. pT
CuCu 200 GeV
ACC
p/?

• Baryon enhancement observed in CuCu at 200 GeV.
• - pT dependence in CuCu is similar to that in
  AuAu.
• gt How about the magnitude as a function of
  centrality? see Next.

NOTE No weak decay feed-down correction applied.
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CuCu 200 GeV vs. AuAu 200 GeV
p/? vs. Npart1/3
- Centrality dependence in CuCu looks similar to
that in AuAu (Npart scaling at same
sqrt(sNN)!). - Even though overlap region has a
different geometrical shape. - Slight difference
in the magnitude seen.
TOF (lt3 GeV/c) ACC (gt3 GeV/c)
NOTE No weak decay feed-down correction
applied.
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p/? vs. pT (Low pT)
- Radial flow -
- Radial flow transverse expansion of the
system - At low pT, p/? shows weak and decreasing
Npart dependence because inverse slope (from mT
exponential fitting) also shows it.
NOTE No weak decay feed-down correction applied.
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p/? vs. pT (Intermediate pT)
TOF, ACC
- Radial flow (ex. blast-wave fit) -

• Spectra for heavier particles has
• a convex shape due to radial flow.
• Using Blast-wave fitting, try to
• estimate p/? ratio as a function of pT.

NOTE No weak decay feed-down correction applied.
(hydro p)/(hydro ?)
(hydro p)/(real ?)

• Hydrodynamic contribution for protons is one of
• the explanations (baryon enhancement).
• - Other contribution is also needed
  Recombination, Jet fragmentation

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p/? vs. pT (Intermediate pT)
ACC
- Quark Recombination -
At intermediate pT, recombination of partons may
be a more efficient mechanism of hadron
production than fragmentation.
A number of models predicted a turnover in the
B/M ratio at pT just above where the available
data finished
Fries, R et al PRC 68 (2003) 044902 Greco, V et
al PRL 90 (2003) 202302 Hwa, R et al PRC 70(2004)
024905 etc.
NOTE No weak decay feed-down correction applied.
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CuCu 62 GeV vs. AuAu 62 GeV
p/? vs. pT
- Again, look at centrality dependence of p/?
ratios. - Similar tendencies as at 200 GeV.
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p/? vs. Npart1/3
CuCu 62 GeV vs. AuAu 62 GeV
TOF
Phenix preliminary

• Npart scaling of p/? also at 62 GeV in
  AuAu/CuCu.

NOTE No weak decay feed-down correction applied.
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p/? vs. Npart1/3 ,(dET/dy)1/3
AuAu 200 GeV vs. AuAu 62 GeV
TOF

• No Npart scaling of p/? (pbar/?) in AuAu
  between 62 GeV and 200 GeV.
• dET/dy scaling of pbar/? seen. gt Proton
  production (at this pT range)
• at 62 GeV is partly from baryon transport, not
  only pair production.
• Nuclear stopping is still large at 62 GeV.

NOTE No weak decay feed-down correction applied.
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(dET/dy)/Npart vs. Npart
R. Armendariz (2006)
- Transverse energy density is a connection key.
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Beam energy dependence of p/?
T. Chujo (QM 06)

• - p/? ratio decreasing as a function of
  ?sNN.
• ?p/?- ratio increasing as a function ?sNN.
• Suggesting a significant contribution of baryon
  
• transport at lower energies.

No weak decay feed-down correction applied.
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Beam energy dependence of p/?
Antiproton is a good probe to study the
excitation function.
No weak decay feed-down correction applied.
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RAA vs. pT
TOF
Phenix preliminary

• Proton, antiproton are enhanced at 1.5 - 4 GeV/c
• for all centralities. (enhancement gt
  suppression)
• - Suppression is seen for pions, kaons.

NOTE No weak decay feed-down correction applied.
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Elliptic Flow
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Elliptic Flow

• Overlap region is like ellipsoid
• at the beginning of collision.
• Spatial anisotropy of the system
• followed by multiple scattering of
• particles (pressure gradient) in the
• evolving system
• - Spatial anisotropy gt momentum anisotropy

Z
Reaction plane
Y
X
Py
Pz
v2 2nd harmonic Fourier coefficient in
azimuthal distribution of particles with respect
to the reaction plane
Px
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A. Taranenko (QM 06)
KET Scaling of v2
nucl-ex/0608033

• KET mTm0
• at y 0

PHENIX preliminary

• Large elliptic flow observed.
• - Mass ordering seen at low pT (lt1.5 GeV/c).
• KET scaling (for hadronic flow) vanish this mass
  
• dependence but give clear splitting of
  meson/baryon v2.

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No.-of-Constituent-Quarks Scaling of v2
nucl-ex/0608033
PHENIX preliminary

• Species dependence of v2 well accounted for
• by scaling v2 and pT (KET) with of quarks.
• Evidence of partonic flow! v2 is developed
  before
• hadrons form.

v2q(pT) v2h(pT/n)/n, v2q(KET) v2h(KET/n)/n
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Eccentricity Scaling of v2
At mid rapidity, v2 (pt,M,b,A)/n
F(KET/n)e(b,A)? e(b,A) integral elliptic flow
of charged hadrons KET transverse kinetic
energy n number of quarks
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M. Shimomura (JPS 06)
Eccentricity Scaling of v2

• - e(b,A)/v2(b,A) 3.1/-0.2
• v2/eccentricity vs. Npart has different slopes
• for different pT.

Black 200GeV Red 62.4GeV
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Energy and System Size dependence of v2
Black AuAu 200GeV Red AuAu 62.4GeV Green CuCu
200GeV Blue CuCu 62.4GeV
v2 is not scaled by Npart.
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Energy and System Size dependence of v2
Black AuAu 200GeV Red AuAu 62.4GeV Green CuCu
200GeV Blue CuCu 62.4GeV
v2 looks rather scaled by eccentricity.
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Summary

• pT reach of PID (especially for p, pbar)
  extended with
• (1) High statistics AuAu/CuCu data
• (2) New PID detector (Aerogel)
• (Anti-)Proton enhancement is observed
• in AuAu/CuCu collisions at 200/62 GeV.
• p/? ratios
• (1) Indicating a transition from soft to hard
  production at intermediate pT.
• (2) Npart scaling (dET/dy scaling) over
  different collision systems.
• (3) Recombination radial flow would explain
  the pT, Npart dependencies.
• - PID v2
• (1) KET scaling, NCQ scaling
• (2) Eccentricity scaling
• - Systematic study of PID spectra, elliptic flow
  (and jet correlations)
• for different collision systems can provide
  information
• to understand the hadron production mechanisms.

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Backup slides
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Beam energy dependence of net protons
nucl-ex/0313023
nucl-ex/0410003
SPS
AGS
- The shape of net proton distribution change
dramatically with beam energy.
- pbar/? ratio could be a good indicator of
thermalization.
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v2 of phi meson
v2 vs KET is a good way to see if v2 for the
f follows that for mesons or baryons v2 /n vs
KET/n scaling clearly works for f mesons as well
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No.-of-Constituent-Quarks Scaling of v2
PHENIX Preliminary
KET/n scaling works for the full measured range
with deviation less than 10 from the universal
scaling curve