Elliptic flow of electrons fromheavy flavor decays

Shingo Sakai for PHENIX Collaborations(Univ. of TsukubaJSPS)Elliptic flow (v2)ｙT Elliptic flowdN/d  N0(1+2v2cos(2))T 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 medium
2006/6/4

ｘ
Initial spatial anisotropy

pｙpｘ

Momentum space anisotropyof particle emission
2v2 already developed in partonic phase ?
T identified hadrons v2 afterscaling pT and v2
number of quarks
T v2 after scaling fall onsame curve
T v2 already formed in thepartonic phase for hadrons
made of light quarks (u,d,s)=> partonic level v2
T charm quark also flow @ RHIC ?

2006/6/4

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Charm quark
T Charm is believed to be produced ininitial collisions via gluon fusion=> total cross-section ; binary scaling (Ncoll)
T Charm propagates throughmedium created in the collisions=> good probe of medium
T initial charm v2 might be 0Phys.Rev.Lett.94:082301,2005=> charm quark v2 due to scattering(PHENIX)
in medium=> non-zero charm v2 indicate
very high dense medium createdin the collision and quark level thermalization

2006/6/44

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%)
2006/6/4

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Charm quarks interact with medium ?
T non-photonic electron RAA
T clear suppression @ high pT
in more central collisoion(RAA < 1.0)=> one of the evidence charm
quarks interact with the medium
T low pT and peripheral collision(centrality > 40 %)is consistent with binary scale
T v2 measurement (pT,cent)gives us additional info. of theinteraction between charm andthe medium

2006/6/4

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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 BBC
T 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-1 = 0

2006/6/4(E-p/p/sigma) distribution7

Non-photonic electron v2 measurement
T Non photonic electron v2 is given as;
dNe/dΦ = dNpho.e /dΦ + dNnon-pho.e /dΦ
=> v2enon-γ = {(1+RNP) v2 - v2eγ} } / RNP
W v2 --- inclusive electron v2
W RNP --- e (non-γ)/ e（γ）
W v2eγ --- photonic electron v2

e (non-γ) / e (γ)
Run04: X=0.4%

T photonic electron v2 determination
Run02: X=1.3%
Wconverter method (experiment)
Measure inclusive electron v2
with/without converter.
(QM05 F. Kajihara)
Then separate non-photonic & photonic e v2
Wcocktail method (simulation)
Determined photonic electron v2 with simulation
2006/6/48

Inclusive electron v2 (in/out converter)

T inclusive electron v2 in / out converter
T difference between converter in / out=> photonic & non-photonic e v2 is different
2006/6/49

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
2006/6/4

10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
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Non-photonic electron v2 (centrality dep.)

T non-photonic electron v2 seems like getting larger with centrality
2006/6/4

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Compare with RAA

T RAA ~ 1.0 @ peripheral collision but v2 still non-zero
T indicate charm quarks interact with medium not only central but also peripheral
2006/6/4

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D meson flow ?
simulation

Phys.Lett.B597:328-332,2004

T electron v2 from D meson decay well reflect parent v2
T non-zero non-photonic electron v2 suggest D meson
also flow @ RHIC
2006/6/4

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expected D v2 from non-photonic e v2TT

expected D v2 from non-γγ v2
process(1) D v2 = a*f(pT)a ; free parameterf(pT) ; pi,K,p(2) D -> e v2
(3) Calculate χ2(4) Find χ2 minimum for “a”
π, deuteron v2 --- PHENIX preliminary

T expected D meson v2 from non-photonic electron v2W smaller than pi v2
W larger than Deuteron v2 “if D v2 shape same as pi, k, p”
Mass D meson~ Mass Deuteron
2006/6/4

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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.
=> favor charm quark flow modelpT[GeV/c]

T assume c v2 < u v2 @ low pT=> mass effect in partonic level ?
0
2006/6/4

1234pT[GeV/c]

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v2

B meson contribution ?
D & B v2- assume D & B v2 sameHendrik, Greco, Rapp
nucl-th/0508055

w.o. B meson (c flow)

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 B meson contribution is model dependent now
but the contribution is getting larger at high pT.
T electron v2 from B meson is smeared due to large mass difference=> high pT single electron v2 is getting smaller ?
2006/6/417

Near future
T single μ v2T new reaction plane detector
W good resolution => reduce error from R.P.
W J/ψψ v2 & high pT non-photonic electron v2
T silicon vertex detector
W direct measurement D meson v2
R=330mm
R=180mmPHENIX
muon arm

R=50mmambe[Silicon vertex detector]
2006/6/4[Reaction plane detector]
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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 v2
T Clear centrality dependence of non-photonic e v2
T Compare with model calculation with charm flow (c v2 < u v2)=> consistent with charm flow model below 2.0 GeV/c=> mass effect in partonic level ?
T Estimate D meson v2 from non-photonic electron v2
assuming D meson v2 shape same as pion, Kaon, proton.

2006/6/4

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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 !
2006/6/4

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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

2006/6/4

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D-> e v2

D meson v2

electron v2

Decay

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D v2 estimate from non-γ e v2 (2)Minimum ; 70 %Minimum ; 75 %Minimum ; 65 %T χ２/ndf v.s. scale factor (a)T current result can’t decide what shape is better.
2006/6/4

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New reaction plane detector

R=330mm
R=180mm
R=50mmPHENIX
muon arm

2006/6/4

TA new reaction plane detector
T position ; 1~|ηη|~2.5,
T resolution ; <cos2∆Φ>∆Φ> ~ 0.7
(BBC ; <cos2ΔΦ
ΔΦ>ΔΦ ~ 0.3)
T materials ;Pb converter + scintillator

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