Shingo Sakai for the PHENIX collaborations (Univ. of Tsukuba)

1. The azimuthal anisotropy of electrons from heavy flavor decays in √SNN = 200 GeV Au-Au collisions by PHENIX Shingo Sakai for the PHENIX collaborations (Univ. of Tsukuba) DNP/JPS

2. Why heavy flavor v2 ? (1)π,K,K0s,p,Λ, Ξ,d ( light quark->u,d,s ) v2 scales approximately with the number of valence quark of hadrons -> indicate partonic level flow if charm quark flow - partonic level thermalization - high density @ the early stage of collision (2) Heavy flavor energy loss - v2@high pT reflects energy loss - if heavy flavor energy loss is small, smaller v2 @ high pT might be expected compared with light quarks v2 M. Djordjevic, M. Gyulassy, R. Vogt, S. Wicks. nucl-th/0507019 DNP/JPS

3. Heavy flavor study @ PHENIX Elecron 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 DNP/JPS

4. e- 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(-))) eID @ RICH After subtract B.G. B.G. Fig : Energy (EMcal) & momentum matching of electrons identified by RICH. Clear electron signals around E-p/p = 0 DNP/JPS (E-p/p/sigma) distribution

5. Non-photonic electron v2 measurement converter method Separate non-photonic & photonic e v2 by using Non-converter run & converter run Non-converter ; Nnc = Nγ+Nnon-γ =>(1+RNP)v2nc = v2γ + RNPv2non-γ Converter ; Nnc = 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)v2 - v2γ} }/RNP Non-pho./pho. Run04: X=0.4% Run02: X=1.3% (QM05 F. Kajihara) DNP/JPS

6. Inclusive electron & photonic electron v2 - inclusive electron v2 (pho. + non-pho.) & photonic electron v2 pT < 1.0 GeV/c --- converter method pT > 1.0 GeV/c --- cocktail method - inclusive electron v2 is smaller than photonic electron v2 - Above 1.0 GeV/c, non-photonic electron contribution is more than 50 % ! photonic e v2 inclusive e v2 Non photonic signal Photonic b.g. DNP/JPS

7. Charm quark flow ? -pT dependence of non-photonic electron v2 after subtracting photonic electron from inclusive electron v2 -Compared with quark coalescence model prediction. D -> e v2 with/without charm quark flow (Greco, Ko, Rapp: PLB 595 (2004) 202) *Due to light quark has finite v2, D meson has non-zero v2 though charm quark v2 = 0 Below 2.0 GeV/c ; consistent with charm quark flow calculation Greco, Ko, Rapp: PLB 595 (2004) 202 DNP/JPS

8. D v2 from non-photonic electron v2 (1) access D meson v2 from non-photonic electron v2 below 2 GeV/c (due to large error & uncertainty B meson contribution above 2 GeV/c) (1) Assume D meson v2 as; v2 D = a * fv2(pT) fv2(pT) = pi v2 fv2(pT) = kaon v2 fv2(pT) = proton v2 fv2(pT) = D v2 (y_T scailing) (2) Calculate D -> e (PYTHIA) (3) D v2 is given as weight to get e v2 (4) chi-squared test with “measured” non-photonic electron v2 below 2 GeV/c χ2 = Σ{(v2 non-γ- v2 D->e)/σv2 }2 (3) Find chi-squared minimum of a chi2 chi2 fv2(pT) = pi v2 fv2(pT) = kaon v2 a(%) a(%) chi2 chi2 fv2(pT) = proton v2 fv2(pT) = D v2 (y_T scal.) a(%) a(%) experiment simulation DNP/JPS

9. D v2 from non-photonic electron v2 (2) • D meson v2 after scaling with chi2 minimum • value (achi2_mim) for each D meson shape (fv2(pT)) • v2 D = achi2_mim * fv2(pT) • fv2(pT) = pi v2 • fv2(pT) = kaon v2 • fv2(pT) = proton v2 • fv2(pT) = D v2 (y_T scailing) • D (= achi2_mim * fv2(pT)) -> e v2 • compared with “measured” • non-photonic electron v2 D meson v2 after scaling with chi2 minimum value (achi2_mim) for each fv2(pT) DNP/JPS

10. Simulation of B->e v2 • - B meson v2 same as D meson v2 • decrease @ high pT • flat @ high pT • - Clear difference electron v2 • from B & D • -If B meson v2 is • Smaller v2 than D meson • decreasing @ high pT • (3) B->e overcome D->e • around 3~4 GeV/c • Non-photonic e v2 might be • reduced. v2 D & B v2 (assume D & B v2 same) B -> e (B v2 flat @ high pT) D -> e B -> e (B v2 decrease @ high pT ) pT DNP/JPS

11. Conclusion • 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 • Access D meson v2 from non-photonic electron v2 assuming D meson v2 shape as pion, Kaon, proton & D meson from y_T scailing. DNP/JPS 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

12. Back up slides DNP/JPS

13. y_T scailing DNP/JPS

14. Photonic Subtraction-Converter Method Ne Inclusive electron yield 1.7% 0.8% ? % 1.1% With converter Conversion in converter Photonic W/O converter Conversion from known material Dalitz : 0.8% X0 equivalent Non-photonic 0 Material amounts: 0 Photon Converter (Brass: 1.7% X0) • Yield of conversion electron can be determined by the radiation length (X0) of material amount. • We know precise X0 of each detector material, but don’t the total effective value (+ air etc.). • However, we can measure the yield of conversion electron by inserting of converter. • Then, the photonic electron is subtracted from inclusive. • Advantage is small systematic error even in low pT region. DNP/JPS F. Kajihara (session CC 7)