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Elliptic Flow in PHENIX. Hiroshi Masui for the PHENIX collaboration CIPANP 2006, Westin Rio Mar Beach Puerto Rico May 30 – Jun 3, 2006. Why Elliptic Flow ?. Z. Study the properties of matter created at RHIC The probe for early time

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elliptic flow in phenix

Elliptic Flow in PHENIX

Hiroshi Masui

for the PHENIX collaboration

CIPANP 2006, Westin Rio Mar Beach

Puerto Rico

May 30 – Jun 3, 2006

why elliptic flow
Why Elliptic Flow ?

Z

  • Study the properties of matter created at RHIC
  • The probe for early time
    • The dense nuclear overlap is ellipsoid at the beginning of heavy ion collisions
    • Pressure gradient is largest in the shortest direction of the ellipsoid
    • Spatial anisotropy  Momentum anisotropy
    • Signal is self-quenching with time
    • Elliptic flow (v2) is defined by the 2nd coefficient of Fourier expansion

Reaction plane

Y

X

Pz

Py

Px

Hiroshi Masui / University of Tsukuba

outline
Outline

partonic

hadronic

Elliptic Flow, v2

  • Bulk, early probe
  • Charged hadrons

give us a base line

direct

Elliptic Flow, v2

time

D

, K, p

Partonic degrees of freedom, Thermalization, ..

 Meson

  • Small interaction cross section, long lived life time (~40 fm/c)

Penetrating probes

  • Heavy flavor electrons (charm)
  • Direct 

Hiroshi Masui / University of Tsukuba

baseline charged hadrons
Baseline : charged hadrons

Charged hadrons, v2 vs pT

PHENIX : PRL 91, 182301 (2003)

  • Large elliptic flow at RHIC
    • Consistent with hydrodynamics with rapid thermalization,  ~ 1 fm/c
    • v2 scales initial eccentricity () of reaction zone

v2 ~ k  

Hiroshi Masui / University of Tsukuba

hydro scaling
Hydro scaling

M. Issah, A. Taranenko, nucl-ex/0604011

Hydro scaling of v2

K0S,  (STAR) : PRL 92, 052302 (2004)

 (STAR) : PRL 95, 122301 (2005)

, K, p (PHENIX) : preliminary

  • Scaling holds up to KET = 1 GeV
  • Meson/Baryon v2
    • Possible hint of partonic degrees of freedom

Meson v2

Baryon v2

* KET ~ mT – m0 at y ~ 0

Hiroshi Masui / University of Tsukuba

1 meson v 2
1.  meson v2

Hiroshi Masui / University of Tsukuba

clear signal
Clear  signal
  •  reconstruction via K+K- decay channel
    • S/N ~ 0.3
  • Centrality 20 – 60 %
    • S/N is good
    • Event plane resolution is good
    • Separation between meson/baryon v2 is good
    • v2 do not be varied too much.

Before subtraction

Signal + Background

Background

After subtraction

Hiroshi Masui / University of Tsukuba

meson type flow
“Meson” type flow !

 v2 vs pT

  • Hydro. mass ordering for pT < 2 GeV/c
  • v2() ~ v2(), v2(K) for pT > 2 GeV/c
    • Mass Number of constituent quarks
      • Consistent with the description by quark coalescence, recombination models

Hiroshi Masui / University of Tsukuba

hint of partonic d o f
Hint of partonic d.o.f

Hydro scaling of v2

K0S,  (STAR) : PR 92, 052302 (2004)

 (STAR) : PRL 95, 122301 (2005)

 (STAR) : preliminary

, K, p, 0, d (PHENIX) : preliminary

  • Hydro + Nquark scaling
    • Works for a broad range of KET
    •  meson also follow the scaling
    • Partonic degrees of

freedom

WWND 2006, M. Issah

Hiroshi Masui / University of Tsukuba

2 heavy flavor electron v 2
2. Heavy flavor electron v2

Hiroshi Masui / University of Tsukuba

clean heavy flavor electron
Clean heavy flavor electron

Cocktail subtraction

Converter subtraction

Signal / Background ratio

  • Two different techniques show an excess heavy flavor electron signal
    • Signal/Background > 1 for pT > 1 GeV/c

Run4

Run2

Hiroshi Masui / University of Tsukuba

hint of charm flow
Hint of Charm flow

e v2 vs pT

V. Greco, C. M. Ko, R. Rapp: PL B 595, 202 (2004)

  • Data indicate finite v2 of charm quark
    • Suggest thermalization of c quark as well as light quarks
  • What is the origin of high pT drop ?

Hiroshi Masui / University of Tsukuba

b quark contribution
b quark contribution ?

e v2 vs pT

H. Hees, V. Greco, R. Rapp: PRC 73, 034913 (2006)

(1)

  • D or B meson v2
  • decrease, (2) flat at high pT

input

(2)

  • High pT drop might be explained by B meson contribution

v2

D  e

output

B  e (1)

Simulation

B  e (2)

SQM 2006, S. Sakai

pT (GeV/c)

Hiroshi Masui / University of Tsukuba

3 direct v 2
3. Direct  v2

Hiroshi Masui / University of Tsukuba

clear direct signal
Clear Direct  signal

PRL 94, 232301 (2005)

  • Large direct  excess
  • 0 is suppressed but direct  not
    • Both results are consistent with pQCD

Hiroshi Masui / University of Tsukuba

possible 3 different scenarios
Possible 3 different scenarios

 v2 vs pT

PRL 96, 032302 (2006)

  • Direct  v2

1. Hard scattering

      • v2 = 0

2. Parton fragmentation

      • v2 > 0

3. Bremsstrahlung

      • v2 < 0
  • Inclusive 
    • Consistent with expected  v2 from hadron decays

Hiroshi Masui / University of Tsukuba

v 2 direct 0
v2direct = 0 ?

 v2 vs pT

PRL 96, 032302 (2006)

  • Direct  v2
    • Direct  excess ratio is consistent with v2BG/v2inclusive, suggest v2direct = 0
    • Favors prompt photon production for dominant source of direct 

Hiroshi Masui / University of Tsukuba

conclusions
Conclusions
  • Elliptic Flow is powerful tool to study hot and dense matter at RHIC
  •  meson  Partonic degrees of freedom
    • Hydro. mass ordering for pT < 2 GeV/c
    • For pT > 2 GeV/c, v2() prefer quark composition not mass
    • Hydro + Nquark scaling works for  meson as well as other hadrons
  • Heavy flavor electron  Thermalization
    • Consistent with non-zero charm flow, suggest thermalization of c quark as well as light quarks
      • Bottom contribution at high pT need to be studied experimentally
  • Direct   Coming soon …
    • v2direct = 0, consistent with the scenario of direct  production from initial hard scattering
      • Year-4 data may enable us to reduce statistical error bars, and extend pT reach, and to measure thermal  v2

Hiroshi Masui / University of Tsukuba

thank you
Thank you

Hiroshi Masui / University of Tsukuba

back up
Back up

Hiroshi Masui / University of Tsukuba

converter subtraction method
Converter Subtraction method

Ne

0.8%

1.1%

? %

1.7%

With converter

Photonic

electron

W/o converter

Photon Converter (Brass 1.7 % X0) around

beam pipe

Conversion from beam pipe

Dalitz :

0.8 % X0 equivalent

Non-photonic electron

0

X0

  • Source of background electrons
  • Photon conversion 0    e+e-
  • Dalitz decay (0ee,  ee, etc)
  • Di-electron decays of , , 
  • Kaon decays
  • Conversion of direct photons

Hiroshi Masui / University of Tsukuba

inclusive electron v 2 w w o converter
Inclusive electron v2 (w., w/o. converter)
  • Converter subtraction method
    • Inclusive electron v2 w. and w/o. converter.
    • Clear difference between them.
    • Electron v2 with converter include large photonic component.

Hiroshi Masui / University of Tsukuba

inclusive photonic electron v 2
Inclusive & photonic electron v2

photonic e v2

  • Photonic electron v2
    • pT < 1 GeV/c

 Converter method

    • pT > 1 GeV/c
    • Simulation
    • v2(inclusive) < v2 (photonic)

 v2(non-photonic) < v2(photonic)

inclusive e v2 (w/o. converter)

Hiroshi Masui / University of Tsukuba

centrality dependence
Centrality dependence
  • Non zero heavy flavor electron v2 !

Hiroshi Masui / University of Tsukuba

run4 inclusive v 2
Run4 inclusive  v2

0

v2

inclusive 

pT

Hiroshi Masui / University of Tsukuba

independent on system size
Independent on system size

Eccentricity scaling

  • Eccentricity scaling
    • A wide range of centrality
    • Independent of system size
  • Integrated v2 eccentricity
    • Reduce systematic error from eccentricity calculation
    • Cancel systematic error by the ratio of v2(pT) / (integrated v2)

Hiroshi Masui / University of Tsukuba

hadron identification
Hadron identification
  • Time-of-flight
    • || < /4, || < 0.35
    • Timing resolution ~ 120 ps
      • /K separation ~ 2 GeV/c
      • K/p separation ~ 4 GeV/c
  • EM Calorimeter
    • || < /2, || < 0.35
    • Timing resolution ~ 400 ps
      • /K separation ~ 1 GeV/c
      • K/p separation ~ 2 GeV/c

Hiroshi Masui / University of Tsukuba

the phenix experiment
The PHENIX experiment
  • Acceptance
    • Central arm: || < , || < 0.35
  • Centrality
    • Beam-Beam Counter, Zero Degree Calorimeter.
  • Event plane
    • BBC
  • Tracking
    • Drift chamber, Pad chambers.
  • Particle identification
    • Electron
      • Electro-Magnetic Calorimeter
    • Hadron
      • Time-of-Flight, Aerogel Cherenkov Counter, EMCal

Hiroshi Masui / University of Tsukuba