The Azimuthal Anisotropy ofElectrons from Heavy Flavor
Decays in √sNN=200 GeV
Au-Au Collisions at PHENIX
Shingo Sakai for PHENIX Collaborations(Univ. of Tsukuba)Azimuthal anisotropyｙT A powerful probe of the initial state of
the high energy heavy ion collision
T transfer initial spatial anisotropy
to momentum space anisotropy
W macroscopic ; hydro model=> pressure gradient
W microscopic=> scattering in the mediumｘ
Initial spatial anisotropy

pｙpdN/d  N0(1+2v2cos(2))ｘ

Momentum space anisotropyof particle emission

2006/5/20HQ 2006 (Shingo Sakai)2v2 already developed in partonic phase ?
T identified hadrons v2 afterscaling number of quarks
T v2 after scaling fall onsame curve
T partonic level v2
T v2 already formed in thepartonic phase for hadrons
made of light quarks (u,d,s)

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Charm quark
T Charm is believed to be produced ininitial collisions via gluon fusion=> total cross-section ; binary scaling
T Charm propagates throughmedium created in the collisions=> good probe of medium

Phys.Rev.Lett.94:082301,2005

T RAA --- suppression @ high pTT initial charm v2 might be 0=> charm quark v2 due to scattering
in medium=> non-zero charm v2 indicate
very high dense medium createdin the collision !
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Charm quark study @ PHENIX
T Electron sources
charm decay
non-photonic
beauty decay
Dalitz decays
Di-electron decays
Photon conversions
Kaon decays
Thermal dileptons

photonic

T Subtract photonic electrons following methods
W“Cocktail subtraction” – calculation of “photonic” electron
background from all known sources
W“Converter subtraction”– extraction of “photonic” electron
background by special run with additional converter(brass, X = 1.7%)
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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
γ
Converter ; Nc = Rγ *Nγ+Nnon-γ => (Rγ +RNP) v2c = Rγ v2γ + RNPv2non-γ
γRγ -- ratio of electrons with & without converter
v2nc --- inclusive e v2 measured with non-converter runv2c --- inclusive e v2 measured with converter runv2γ --- photonic e v2,v2non-γ
γ --- non photonic e v2

cocktail method

Run04: X=0.4%

Determined photonic electron v2 with simulation
Then subtract it from electron v2 measured withnon-converter run
v2non-γ
γ = {(1+RNP)v2nc - v2γ} }/RNP
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Non-pho./pho.

HQ 2006 (Shingo Sakai)

Run02: X=1.3%(QM05 F. Kajihara)
6Electron v2 measurement @ PHENIX
T Electron v2 is measured by R.P.
methoddN/d(φφ-ΦΦ) = N (1 + 2v2obscos(2(φφ-ΦΦ)))
T R.P. --- determined with BBCT Tracking (pT,φ) --- DC + PC
T electron ID --- RICH & EMCale-eID @ RICH
After subtract B.G.
B.G.

Fig : Energy (EMcal) & momentum matchingof electrons identified by RICH.
Clear electron signals around E-p/p = 0

2006/5/20(E-p/p/sigma) distribution
HQ 2006 (Shingo Sakai)

7Inclusive electron v2 (in/out converter)

T inclusive electron v2 in / out converter
T clear difference between converter in / out=> photonic & non-photonic e v2 is different
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8Inclusive electron & photonic electron v2○ photonic electron v2 (converter method)

photonic electron v2 (simulation ; pi0 -> e)
inclusive electron v2 (converter out)

T compare with inclusive & photonic electron v2
T photonic e v2 ; pT < 1.0 (conv.) & pT > 1.0 (cock.)
T inclusive electron v2 is smaller than photonic electron v2
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9Non-photonic electron v2

T Non-photonic electron v2 : pT < 1.0 (conv.) & pT>1.0 (cock.)
T Non-photonic electron v2 has non-zero v2=> indicate non-zero D meson v2
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10Charm quark flow ?
T Compared with quark
coalescence model prediction.
with/without charm quark flow
(Greco, Ko, Rapp: PLB 595 (2004) 202)
- No Bottom contribution- c v2 small u v2 @ low pT- quark v2 flat @ high pT

T Below 2.0 GeV/c ;consistent with charm quark
flow model.

pT[GeV/c]

T non-photonic electron v2
favor charm quark flow model0
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3

4

pT[GeV/c]11

D v2 estimate from non-γ e v2 (1)(1) different v2(pt) shape assumptions
for D meson ;v2
D v2 = a * f(pT)
f(pT) = pi v2 / k v2 / p v2
Change “a”
a ; free parameter(2) Simulate D -> e
* pT distribution tuned
to reproduce electron spectra
shape at Au+Au

D meson v2 is assumed
v2 D = a * f(pT)(f.e. v2 D = 0.6*pi v2)

a ; free parameterpTSimulate D -> ev2--- D -> e
non-p e v2(3) χ2 restricted up to pT<2GeV/c(due to uncertainty of B contribution)

χ2 = ΣpT{(v2 non-γ e(pT) - v2 D->e (pT))/σv2 }2(4) Change “a” and find χ2 minimum for each f(pT)
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HQ 2006 (Shingo Sakai)pT
χ２ test12

D v2 estimate from non-γ e v2 (2)Minimum ; 70 %Minimum ; 75 %Minimum ; 65 %T χ２/ndf v.s. scale factor (a)T D meson v2 might be smaller than pi, K, p v2
2006/5/20HQ 2006 (Shingo Sakai)

13Compare D v2 with other hadron v2π, deuteron v2 --- PHENIX preliminary

T expected D meson v2 from non-photonic electron v2 (pT < 2.0 GeV/c)
W smaller than pi v2
W larger than Deuteron v2 if D v2 shape same as pi, k, p
(Mass D meson~ Mass Deuteron)
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Summary
T Non-photonic electron v2 from heavy flavor decays
has been measured with RHIC-PHENIXT Non-photonic electron v2 has non-zero v2=> indicate non-zero D meson v2T Compare with model calculations assuming
charm flow or not
Our result consistent with charm flow model below
2.0 GeV/c
T Estimate D meson v2 from non-photonic electron v2
assuming D meson v2 shape as pion, Kaon, proton.
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T Backup slides

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Converter method
Separate non-photonic & photonic e v2 by using
Non-converter run & converter run
Non-converter ; Nnc = Nγ+Nnon-γ
Converter ; Nc = Rγ *Nγ+Nnon-γ(1+RNP)v2nc = v2γ + RNPv2non-γγ(Rγ +RNP) v2c = Rγ v2γ + RNPv2non-γγRγ --- 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)v2non-γγ(non-photonic) & v2γ(photonic) is“experimentally” determined !
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Cocktail method
Determined photonic electron v2 with simulation
Then subtract it from electron v2 measured
with non-converter rundNe/dΦ = dNpho.e /dΦ + dNnon-pho.e /dΦv2non-γ
γ = {(1+RNP) v2 - v2γ} } / RNP
measuredmeasured

calculate

RNP --- non-photonic/photonic ratio
experimentally determinedv2 --- inclusive electron v2 (without converter)v2γ --- photonic electron v2
calculated from pi0 (pion) v2

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v2

B meson contribution to non-γ.e. v2
D & B v2- assume D & B v2 same
Hendrik, Greco, Rapp
nucl-th/0508055

w.o. B meson (c flow)- v2 ~ 0.6 pi v2
D -> ew. B meson (c,b flow)

T based on quark coalescence model
T c, b reso ; c,b get v2 by elastic scat. in QGP

B -> epTT Model predict B -> e v2 reduce non-photonic electron v2 @ high pT
T if B meson v2 saturate @ high pT, non-photonic electron v2 reduce
due to smearing of electron v2 from B meson.
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