1 Measurement of Heavy Quark production at RHIC-PHENIX Yuhei Morino CNS, University of Tokyo

2 flow & energy loss ? insight into the property of the medium 1.Introduction Heavy quarks (charm and bottom) is produced in initial collision  good probe for studying property of the medium. small energy loss and large thermal equilibration time are expected due to their large mass. RHIC is for the study of extreme hot and dense matter. p+p, d+Au, Cu+Cu, Au+Au collision √s = 22.4, 62, 130, 200 GeV A.

3 2.PHENIX experiment PHENIX central arm: –|  | < 0.35 –  = 2 x  /2 –p > 0.2 GeV/c Charged particle tracking analysis using DC and PC → p Electron identification –Ring Imaging Cherenkov detector (RICH) –Electro- Magnetic Calorimeter (EMC) → energy E

4 electron/muon from semileptonic decay ++ direct measurement: D  K , D  K  MesonD ±,D 0 Mass1869(1865) GeV BR D 0 --> K  (3.85 ± 0.10) % BR --> e +XD ± : 17.2, D 0 : 6.7 % 3.Heavy quark measurement at PHENIX

5 Upper limit of FONLL PRL, 97, (2006)  cc = 567  57(stat) ± 224(sys)  b FONLL: Fixed Order plus Next to Leading Log pQCD Central value for data/FONLL predictions ~1.7 ( reasonable value) Inclusive electron (  conversion,  daliz,etc and heavy quark ) Background subtraction Non-photonic electron (charm and bottom) 3.2 Result of p+p at  s NN = 200 GeV

6 3.3 Result of Au+Au at  s NN = 200 GeV MB p+p 0%~ ~92% Heavy flavor electron compared to binary scaled p+p data (FONLL*1.71) Clear high pT suppression in central collisions PHENIX PRL (2007)

7 3.4 Nuclear Modification Factor: R AA large suppression! Radiative energy loss does not describe!. dead cone effect PHENIX PRL (2007) Djordjevic, PLB (2006)

8 3.5 Non-photonic electron v 2 Greco, Ko, Rapp: PLB 595 (2004) 202 data suggests non-zero charm v 2  charm is strongly coupled to the matter. pQCD fail [PRB637,362]

9 3.6 comparison with models. pQCD radiative E-loss with 10-fold upscaled transport coeff. elastic pQCD + D resonances + coalescence 2-6 upscaled pQCD elastic various models exist. These calculations suggest that D HQ (~(3~6)/2  T..near quantum bound) are required to reproduce the data. PLB649(2007)139 Collisional dissociation  heavy quarks can fragment inside the medium and can be suppressed by dissociation b  e R AA c  e R AA behavior of bottom differ from charm  c/b separation is necessary for further discussion.

10 4. B contribution to non-photonic electron FONLL: Fixed Order plus Next to Leading Log pQCD calculation Large uncertainty on c/b crossing 3 to 9 GeV/c Experimental determination of c  e/b  e is one of most important next steps FONLL:

11 electron/muon from semileptonic decay ++ Heavy quark measurement at PHENIX D  e K partial reconstruction

12 5 c  e/b  e via e-h correlation N tag = N unlike - N like unlike sign e-h pairs contain large background from photonic electrons.  like sign pair subtraction (N tag is from semi-leptonic decay) From real data analysis N c(b)  e is number of electrons from charm (bottom) N c(b)  tag is N tag from charm (bottom) From simulation (PYTHIA and EvtGen)  data can be written by only charm and bottom component The tagging efficiency is determined only decay kinematics and the production ratio of D(B)hadrons to the first order(85%~). Main uncertainty of  c and  b  production ratios (D + /D 0, D s /D 0 etc) contribution from NOT D(B) daughters

13 theoretical uncertainty is NOT included. comparison of data with simulation (0.5~5.0 GeV) pt(e) 2~5GeV/c  2 /ndf 5.2 c  e/b  e via e-h correlation Year5 p+p  s=200GeV data set is used

14 (b  e)/(c  e+b  e) as a function of electron pt (b max) and (c min) ( b min) and (c min) (b min) and (c max) (b max) and (c max) 5.3 c  e/b  e via e-h correlation Year5 p+p  s=200GeV data set is used

15 ++ direct measurement: D 0  K +     D 0  K +  - Heavy quark measurement at PHENIX MesonD ±,D 0 Mass1869(1865) GeV BR D 0 --> K +  ± 0.10 % BR D 0 --> K +  -  ± 0.10 % BR --> e + +X17.2(6.7) % BR -->  +  +X 6.6 %

16 6. Direct measurement of D 0 Year5 p+p  s=200GeV data set is used Observe 3  significant signal in p T D range 5 ~ 15 GeV/c No clear signal is seen for p T D < 5 GeV/c The signal is undetectably small for p T D > 15 GeV/c Signal is fitted with parabola(B) + gaussian(S) D 0  K +  -  + reconstruction

17 Momentum Dependence Observe clear peak in all p T bins from 5 GeV/c to 10 GeV/c Fits are parabola + gaussian Background is uniform within fitting range 6.2 Direct measurement of D 0 D 0  K +  -  + reconstruction Analysis to determine invariant cross section is on going.

Direct measurement of D 0 D 0  K +  - reconstruction with electron tag tag reconstruct real event mixing event back ground subtracted observe D 0 peak Analysis to determine invariant cross section is on going Year5 p+p  s=200GeV data set is used

19 Summary and outlook A large suppression pattern and azimuthal anisotropy of single electron has been observed in Au+Au collisions at √s NN =200GeV. b  e/(c  e + b  e) has been studied in p+p collisions at √s =200GeV via e-h correlation for further discussion.  analysis for more statistics and high pt extension is on going Clear peak of D 0 meson observed in p+p collisions at √s =200GeV in D 0  K +  -  0 and D 0  K +  -  channels.  Analysis to determine invariant cross section is on going. The results of direct measurement will be compared with the results of measurement via semi-leptonic decay

20 back up

21 Singnal and Background Photon Conversion Main photon source:    →  In material:  → e + e - (Major contribution of photonic electron) Dalitz decay of light neutral mesons    →  e + e - (Large contribution of photonic) The other Dalitz decays are small contributions Direct Photon (is estimated as very small contribution) Heavy flavor electrons (the most of all non-photonic) Weak Kaon decays K e3 : K ± →   e ± e ( 1.0 GeV/c) Vector Meson Decays  J  → e + e -  (< 2-3% of non-photonic in all p T. ) Photonic Electron Non-photonic Electron

22 Most sources of background have been measured in PHENIX Decay kinematics and photon conversions can be reconstructed by detector simulation Then, subtract “cocktail” of all background electrons from the inclusive spectrum Advantage is small statistical error. Background Subtraction: Cocktail Method

23 Background Subtraction: Converter Method We know precise radiation length (X 0 ) of each detector material The photonic electron yield can be measured by increase of additional material (photon converter ) Advantage is small systematic error in low p T region Background in non-photonic is subtracted by cocktail method N e Electron yield Material amounts:  0 0.4%1.7% Dalitz : 0.8% X 0 equivalent radiation length 0 With converter W/O converter 0.8% Non-photonic Photonic converter

24 Consistency Check of Two Methods Both methods were checked each other Left top figure shows Converter/Cocktail ratio of photonic electrons Left bottom figure shows non-photon/photonic ratio

25 charm production bottom production charm  c = (sys) bottom  b = (sys) 4. Analysis(2) unlike pair like pair From real data Electron pt 2~5GeV/c Hadron pt 0.4~5.0GeV/c count X 1/N non-phot e  data (stat) (sys) From simulation (PYTHIA and EvtGen) Electron pt 2~5GeV/c Hadron pt 0.4~5.0GeV/c unlike pair like pair (unlike-like) /# of ele

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27 5. Result (electron P t 2~3GeV/c) theoretical uncertainty is NOT included. comparison of data with simulation (0.5~5.0 GeV) pt(e) 2~5GeV/c  2 /ndf pt(e) 2~3GeV/c  2 /ndf

28 5. Result (electron P t 3~4GeV/c) theoretical uncertainty is NOT included. comparison of data with simulation (0.5~5.0 GeV) pt(e) 2~5GeV/c  2 /ndf pt(e) 2~3GeV/c  2 /ndf pt(e) 3~4GeV/c  2 /ndf

29 theoretical uncertainty is NOT included. comparison of data with simulation (0.5~5.0 GeV) pt(e) 2~5GeV/c  2 /ndf pt(e) 2~3GeV/c  2 /ndf pt(e) 3~4GeV/c  2 /ndf pt(e) 4~5GeV/c  2 /ndf 5. Result (electron P t 4~5GeV/c)

30 6.Discussion Collisional dissociation in hot and dense matter? Input b  e/c  e  heavy quarks can fragment inside the medium and can be suppressed by dissociation suppression of non-photonic electron is not so strong as prediction by collisional dissociation model.

31 Open Charm in p+p STAR vs. PHENIX PHENIX & STAR electron spectra both agree in shape with FONLL theoretical prediction Absolute scale is different by a factor of 2 31

32 p+p 200 GeV Fit e-h correlation with PYTHIA D and B Data shows non-zero B contribution STAR QM2006 Bottom !

33 Photon Converter e+e+ e-e-

34 Non-photonic electron v 2 measurement Non photonic electron v 2 is given as; v 2 γ.e ; Photonic electron v 2  Cocktail method (simulation) stat. advantage  Converter method (experimentally) v 2 e ; Inclusive electron v 2 => Measure R NP = (Non-γ e) / (γ e) => Measure page4 (1) (2)

35 Inclusive electron v 2 inclusive electron v 2 measured w.r.t reaction plane converter --- increase photonic electron photonic & non-photonic e v 2 is different page6

36 Photonic e v 2 determination good agreement converter method (experimentally determined) photonic electron v 2 => cocktail of photonic e v 2 page7 R = N X->e / N γe photonic e v 2 (Cocktail) decay v 2 (π 0 ) pT<3 ; π (nucl-ex/ ) pT>3 ; π 0 (PHENIX run4 prelim.)