1. Shingo Sakai for PHENIX Collaborations (Univ. of Tsukuba)
The Azimuthal Anisotropy of Electrons from Heavy Flavor Decays in √sNN=200 GeV Au-Au Collisions at PHENIX
Shingo Sakai for PHENIX Collaborations
(Univ. of Tsukuba)

2. Method of electron v2 measurement from heavy flavor decay Results
OutLine
Motivation
Method of electron v2 measurement
from heavy flavor decay
Results
Compare with model
B meson contribution
Expected D meson v2
Summary
2006/3/26
SQM2006 (Shingo Sakai)

3. Why heavy flavor v2 ? π,K,K0s,p,Λ, Ξ ; ( light quark->u,d,s )
v2 scales approximately with
the number of valence quark of hadrons
-> indicate partonic level flow
　　　for u,d,s
if charm quark also flow
- partonic level thermalization
- high the early stage of collision
The motivation of this measurement is two. One is heavy flavoe flow and the other is energy loss. The right figure shows the identified particle v2 scaled with number of quarks. These v2 are well scaled and that means the v2 already develop in partonic level. If charm quark flow it indicates that the partonic level thermalization and high the early stage of collision.
The bottom figure show the Raa for the quarks. The model predict that the heavy flavor energy loss is small compared with light quark. V2 is thought that the reflect energy loss therefore if heavy flavor energy loss is smaller, smaller v2 might be expected compared with light quarks high pT.
2006/3/26
SQM2006 (Shingo Sakai)

4. Heavy flavor study @ PHENIX
Electron sources
charm decay
beauty decay
Dalitz decays
Di-electron decays
Photon conversions
Kaon decays
Thermal dileptons
　Subtract photonic electrons following methods
“Cocktail subtraction” – calculation of “photonic” electron background from all known sources
“Converter subtraction”– extraction of “photonic” electron background by special run with additional converter
　(brass, X = 1.7%)
non-photonic
photonic
2006/3/26
SQM2006 (Shingo Sakai)

5. Non-photonic electron v2 measurement
converter method
Measure inclusive electron v2 with/without converter
Then separate non-photonic & photonic e v2
Non-converter ; Nnc = Nγ+Nnon-γ => (1+RNP)v2nc = v2γ + RNPv2non-γ
Converter ; Nc = R *Nγ+Nnon-γ => (R +RNP) v2c = R v2γ + RNPv2non-γ
R -- ratio of electrons with & without converter
　 v2nc --- inclusive e v2 measured with non-converter run
　 v2c --- inclusive e v2 measured with converter run
v2γ --- photonic e v2,
v2non-γ --- non photonic e v2
cocktail method
Determined photonic electron v2 with simulation
Then subtract it from electron v2 measured with
non-converter run
v2non-γ = {(1+RNP)v2nc - v2γ} }/RNP
Non-pho./pho.
Run04: X=0.4%
Run02: X=1.3%
(QM05 F. Kajihara)
2006/3/26
SQM2006 (Shingo Sakai)

6. Electron v2 measurement @ PHENIX
Electron v2 is measured by R.P. method
R.P. --- determined with BBC
Tracking (pT,φ)　--- DC + PC
electron ID --- RICH & EMCal
dN/d(-) = N (1 + 2v2obscos(2(-)))
RICH
After subtract B.G.
Energy (EMcal) & momentum matching
B.G.
Fig : Energy (EMcal) & momentum matching
of electrons identified by RICH.
Clear electron signals around E-p/p = 0
2006/3/26
SQM2006 (Shingo Sakai)
(E-p/p/sigma) distribution

7. Inclusive electron v2 (in/out converter)
clear difference between
converter in / out
converter in electron v2
include large photonic
component
2006/3/26
SQM2006 (Shingo Sakai)

8. Inclusive electron & photonic electron v2
inclusive & photonic electron v2
pT < 1.0 GeV/c --- conv. method
pT > 1.0 GeV/c --- simulation
inclusive electron v2 is smaller
than photonic electron v2
=> non-photonic electron v2
is smaller than photonic electron v2
photonic e v2
inclusive e v2
(w.o. converter)
Inclusive electron v2
2006/3/26
SQM2006 (Shingo Sakai)

9. Non-photonic electron v2
pT < 1.0 GeV/c --- conv. method
pT > 1.0 GeV/c --- cock. method
Indication for reduction of v2 at pT > 2 GeV/c ; Bottom contribution??
Compared with quark
coalescence model prediction.
with/without charm quark flow
(Greco, Ko, Rapp: PLB 595 (2004) 202)
Below 2.0 GeV/c ;
consistent with charm quark
flow model.
indicate charm quark flow 1
2006/3/26
SQM2006 (Shingo Sakai) 1 2 3

10. B meson contribution to non-γ.e. v2pT
D & B v2
- assume D & B v2 same
- v2 ~ 0.6 pi v2 v2
Hendrik, Greco, Rapp
nucl-th/
w.o. B meson (c flow)
D -> e
w. B meson (c,b flow)
based on quark coalescence model
c, b reso ; c,b get v2 by elastic scat. in QGP
B -> e
w. b meson
w.o. b meson
Model predict B -> e v2 reduce non-photonic electron high pT
e v2 from B meson is smeared due to large mass difference
2006/3/26
SQM2006 (Shingo Sakai)

11. D v2 estimate from non-γ e v2
Estimate D meson v2 with non-γe v2
(below 2.0 GeV/c)
Assuming several v2 shape for
D meson v2
Dv2(pT) = api * pi v2
Dv2(pT) = aK * kaon v2
Dv2(pT) = ap * proton v2
Calculate D -> e
chi-squared test with
“measured” non-photonic electron v2
find chi-squared minimum “a”
for pi, K, p (api, aK and ap)
D meson v2
Decay
electron v2
Decay
2006/3/26
SQM2006 (Shingo Sakai)

12. Compare D v2 with other hadron v2
π, deuteron v2 --- PHENIX preliminary
Π, deuteron v2 --- PHENIX preliminary
　expected D meson v2 from non-photonic electron v2 (pT < 2.0 GeV/c)
smaller than pi v2
larger than Deuteron v2 (Mass D meson~ Mass Deuteron)
2006/3/26
SQM2006 (Shingo Sakai)

13. Non-photonic electron v2 from heavy flavor decays has been measured
Summary
Non-photonic electron v2 from heavy flavor decays
has been measured with RHIC-PHENIX
Compare with model calculations assuming
charm flow or not
Our result consistent with charm flow model below
2.0 GeV/c
B meson contribution might be reduce non-photonic e v2
@ high pT
Estimate D meson v2 from non-photonic electron v2
assuming D meson v2 shape as pion, Kaon, proton.
2006/3/26
SQM2006 (Shingo Sakai)
Non-photonic electron v2 from heavy flavor decays has been measured
with RHIC-PHENIX
Compare with model calculations assuming charm flow or not
=>Out result consistent with charm flow model at low pT
Compare with PYTHIA calculation.
D meson v2 --- scaled pion v2
=>Indicate D meson v2 is smaller than pion v2

14. Backup slides
2006/3/26
SQM2006 (Shingo Sakai)

15. Azimuthal anisotropy ｙ ｘ pｙ pｘ dN/dφ ∝ N0(1+2v2cos(2φ))
A powerful probe of the initial state of
the high energy heavy ion collision
Low pT
pressure gradient of
early stage of collision
High pT
parton energy loss in hot &
dense medium
Initial spatial anisotropy pｘ pｙ
Spatial anisotropy
Thermal equilibrium
The azimuthal anisotropy of particle emission is sensitive to the early stages of system evolution
Probe of jet quenching
Hydro model
Measurement of identified particle v2 give up much more
Information of the collision dynamics
Momentum space anisotropy
of particle emission
　　dN/dφ ∝ N0(1+2v2cos(2φ))
2006/3/26
SQM2006 (Shingo Sakai)

16. “experimentally” determined !
Converter method
Separate non-photonic & photonic e v2 by using
Non-converter run & converter run
Non-converter ; Nnc = Nγ+Nnon-γ
Converter ; Nc = R *Nγ+Nnon-γ
(1+RNP)v2nc = v2γ + RNPv2non-γ
(R +RNP) v2c = R v2γ + RNPv2non-γ
v2non-γ(non-photonic) & v2γ(photonic) is
“experimentally” determined !
R --- ratio of electrons with & without converter (measured)
RNP --- non-photonic/photonic ratio (measured)
v2nc --- inclusive e v2 measured with non-converter run (measured)
　v2c --- inclusive e v2 measured with converter run (measured)
2006/3/26
SQM2006 (Shingo Sakai)

17. Cocktail method Determined photonic electron v2 with simulation
Then subtract it from electron v2 measured
with non-converter run
dNe/d = dNpho.e /d + dNnon-pho.e /d
v2non-γ = {(1+RNP) v2 - v2γ} } / RNP
measured
measured
calculate
RNP --- non-photonic/photonic ratio
experimentally determined
v2 --- inclusive electron v2 (without converter)
v2γ --- photonic electron v2
calculated from pi0 (pion) v2
From F. Kajihara
2006/3/26
SQM2006 (Shingo Sakai)