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Open heavy flavor measurements at PHENIX

Open heavy flavor measurements at PHENIX. Y. Akiba (RIKEN) for PHENIX Nov. 2, 2007 LBNL Heavy Quark Workshop. Outline. Single electron measurements Details of the analysis Cross section in pp Spectra in AuAu and RAA v2 Single muon (New) Method result

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Open heavy flavor measurements at PHENIX

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  1. Open heavy flavor measurements at PHENIX Y. Akiba (RIKEN) for PHENIX Nov. 2, 2007 LBNL Heavy Quark Workshop

  2. Outline • Single electron measurements • Details of the analysis • Cross section in pp • Spectra in AuAu and RAA • v2 • Single muon (New) • Method • result • b/c ratio from e-h charge correlation (New) • Method • result • D0  K-p+p0 (New) • Summary

  3. Heavy Quark Measurement Direct Measurement: DKp, DKpp Indirect Measurement via Semileptonic decays p+

  4. PHENIX single e measurements Published • Au+Au 130 GeV • PRL88,192303(2002) First charm measurement at RHIC • Au+Au 200 GeV • PRL94,082301(2005) Ncoll scaling of total charm yield • PRL96,032301(2006) Observation of suppression at high pT • PRC72,024901(2005) First measurement of v2(e) • PRL98,172301(2007) High statistic RAA and v2; h/s • p+p 200 GeV • PRL96,032001(2006) First pp baseline measurement • PRL97,252002(2006) High statistic pp baseline Preliminary • d+Au 200 GeV • QM2004 Ncoll scaling • Au+Au 62 GeV

  5. Inclusive e± measurement: roadmap e- • PHENIX central arm coverage: • |h| < 0.35 • Df = 2 x p/2 • p > 0.2 GeV/c • typical vertex selection: |zvtx| < 20 cm • charged particle tracking analysis using DC and PC1 • electron identification based on • Ring Imaging Cherenkov detector (RICH) • Electro-Magnetic Calorimeter (EMC)

  6. Electron identification • Electron identificaition is very easy for pT<5 GeV/c • After RICH hit is required, basically all tracks are electrons • Electron signal is clearly visible in E/p ratio distribution (the peak ~ 1 is electron) • The tail part is due to off vertex conversion and Ke3 decay. • MC reproduces the distribution very well. • In the plots, the data and the MC are absolutely normalized Data MC (p0+Ke3) p0 Dalitz and g Conversion (MC) Data Ke3 decay BG(MC) MC (p0+Ke3)

  7. Electron Signal and Background Photon conversions p0 → g g, g→ e+ e- in material Main background Dalitz decays p0 → ge+ e- Direct Photon Small but significant at high pT Measured by PHENIX Heavy flavor electrons D → e± + X Weak Kaon decays Ke3: K± → p0e±e < 3% of non-photonic in pT > 1.0 GeV/c Vector Meson Decays w, , fJ → e+e- < 2-3% of non-photonic in all pT Photonic electron Non-photonic electron • Background is subtracted by two independent techniques: • Cockail Method • Converter method

  8. Background Subtraction: Cocktail Method 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.

  9. Inclusive vs cocktail Inclusive – cocktail = heavy flavor signal Inclusive electrons Cocktail calculation pT (GeV/c)

  10. Converter subtraction: idea e+ γ e- Converter e+ p e- p • introduce additional converter in PHENIX acceptance for a limited time • 1.68 % X0 brass foil close to beam pipe • increases yield of photonic electrons by a fixed factor • comparison of spectra with and without converter installed allows to separate electrons from photonic and non-photonic sources Photon Converter Reality

  11. Converter subtraction: the calculation PRL 94(2005)082301 (run2 AuAu) • electron yields: • useful definitions: • then: simulated calculated from this equation! measured

  12. RCN in p+p Run-5 Rg Expected for Pure photonic Non-photonic signal Measured RCN • RCN is ratio of “raw” electron spectra! • signal/background is LARGE (see next slide) and increases as function of pT!

  13. Cross-check: Cocktail vs Photonic (measured) Red: Measured photonic electron spectrum using the converter method Curve: Cocktail calculation pT(GeV/c) Photonic electron Measured/Cocktail=0.94±0.04 Consistent within cocktail systematic error  Used to re-normalize cocktail

  14. Singnal/Backgroud of Heavy Flavor electrons • S/B = 0.1 to ~3 • Large S/B is due to small conversion material in PHENIX acceptance

  15. Run-5 p+p Result at s = 200 GeV PRL97,25 Heavy flavor electron compared to FONLL Data/FONLL = 1.71+/- 0.019 (stat)+/- 0.18 (sys) FONLL agrees with data within errors All Run-2, 3, 5 p+p data are consistent within errors Total cross section of charm production: 567 mb+/- 57 (stat) +/- 224 (sys) Upper limit of FONLL

  16. Total Charm Crossection New charm total crossection:

  17. Run-4 Au+Au Result at sNN = 200 GeV Submitted to PRL (nucl-ex/0611018) Heavy flavor electron compared to binary scaled p+p data (FONLL*1.71) Clear high pT suppression in central collisions S/B > 1 for pT > 2 GeV/c (according to inside figure) MB p+p

  18. Nuclear Modification Factor: RAA Total error from p+p Suppression level is the almost same asp0 andhin high pT region Binary scaling works well for p’T>0.3 GeV/c integration (Total charm yield is not changed)

  19. Elliptic Flow: v2 Kaon contribution is subtracted • Elliptic flow: dN/dφ ∝ N0(1+2 v2 cos(2φ)) Collective motion in the medium • v2 forms in the partonic phase before hadrons are made of light quarks (u/d/s) →partonic level v2 • If charm quarks flow, • - partonic level thermalization • - high density at the early stage • of heavy ion collisions Non-zero elliptic flow for heavy-flavor electron → indicatesnon-zero D v2

  20. RAA and v2 of Heavy Flavor Electrons PRL, 98, 172301 (2007) • Only radiative energy loss model can not explain RAA and v2 simultaneously. • Rapp and Van Hees • Phys.Rev.C71:034907,2005 • Simultaneously describes RAA and v2 with diffusion coefficient in range: DHQ × 2πT ~ 4 – 6 • Assumption: elastic scattering is mediated by resonance of D and B mesons. • They suggest that small thermalization time τ(~ a few fm/c) and/or DHQ. Comparable to QGP life time.

  21. Heavy flavor measurement by single muons • PHENIX can measure open heavy flavor in forward rapidity via single muons • So far, results from RUN2 pp at 200 GeV is published. • Relatively large systematic unceratinties • Limited statistics • new analysis of RUN5pp data is on going with better systematic uncertainties and higher statistics hep/ex0609032 PRD in proof

  22. Dominant sources of tracks in the muon arm 0 1 2 3 4 Gap: Muon from heavy flavor (the signal) PHENIX Detector Hadron (does not interact and punches through the entire detector) A muon from hadron decay An interacting hadron (nuclear interaction) A low energy muon that ranges out due to ionization energy loss (primarily hadron decay muons) Analysis by D. Hornback (U. Tennessee)

  23. Methodology of this single muon analysis 0 1 2 3 4 PHENIX Detector Gap: Simultaneous matching of background hadron cocktail and data: 1. of measured stopped hadrons in gaps 2 and 3 2. and of z-vertex distributions for gap 4 muons from hadron decay The ~10λ of steel is a problem however.

  24. matching hadrons for simulation and data Gap 3 stopped hadron yield Gap 2 stopped hadron yield ≈1 for a a good hadron shower code ≡1 by definition A cocktail of hadrons are fully simulated in the muon arm. This background estimate is normalized to match data at gap 3.

  25. matching z-vertex distributions at gap 4 pT=1.0-1.25 pT=1.25-1.5 pT=1.5-1.75 pT=1.75-2.0 invariant yield pT=2.0-2.25 pT=2.25-2.5 pT=2.5-2.75 pT=2.75-3.0 Z (cm) Black: data Blue: total cocktail Redand green: pion/kaon components Matching z-vertex distribution slopes → proper hadron decay muon determination

  26. Heavy flavor muon invariant cross section • p+p at 200 GeV. Run5 prelimianry result

  27. Comparison with RUN2 results • The new RUN5 muon data is somewhat lower than the RUN2 results (nucl-ex/0609032; accepted in PRD) run2

  28. Comparison with electron data • Observed cross sections are similar to that of electron at y~0 • Data/FONLL ratio is ~ 2 for high pT

  29. Measurement of b/c ratioviaelectron-hadron charge correlation

  30. Using the charge correlation to measure ce So far we do not separate ce and be components of heavy-flavor electrons. Here we separate ce component using the charge correlation of K and e from D-meson decay. If D-meson decays into charged kaon and electron, their charges are opposite: Thus one can determine the fraction of ce component by measuring the fraction associated with opposite sign kaon, or opposite sign charged hadron Charged kaon and lepton from D decay has opposite charge Actual analysis is done as e-h charge correlation (i.e. no kaon PID) for higher statistic

  31. Details of the Analysis unlike sign e-h pairs contain large background from photonic electrons. like sign pair subtraction (Ntag is from semi-leptonic decay) Ntag = Nunlike - N like From real data analysis Nc(b)e is number of electrons from charm (bottom) Nc(b)tag is Ntag from charm (bottom) edata can be written by only charm and bottom component From simulation (PYTHIA and EvtGen) The tagging efficiency is determined only decay kinematics and the production ratio of D(B)hadrons to the first order(85%~). Main uncertainty of ec and eb  • production ratios (D+/D0, Ds/D0 etc) • contribution from NOT D(B) daughters Analysis by Y. Moritno

  32. edata 0.029 +- 0.003(stat) +- 0.002(sys) X 1/Nnon-phot e From real data count Electron pt 2~5GeV/c Hadron pt 0.4~5.0GeV/c unlike pair like pair bottom production charm production Details of the Analysis(2) After like-sign subtraction From simulation (PYTHIA and EvtGen (B decay MC) ) charm ec = 0.0364 +- 0.0034(sys) bottom eb = 0.0145 +- 0.0014(sys) Electron pt 2~5GeV/c Hadron pt 0.4~5.0GeV/c unlike pair like pair (unlike-like) /# of ele Charge correlation in b-decay and/or for high mass are due to charge conservation

  33. Result theoretical uncertainty is NOT included. comparison of data with simulation (0.5~5.0 GeV) pt(e) 2~5GeV/c c2 /ndf 58.4/45 @b/(b+c)=0.34 Yield of (unlike-like) in the data is between the expectation of ce and be Extract b/c ratio from the data/simulation comparison

  34. Tagging efficiency as function of pT • If electrons are purely from charm decay, tagging efficiency should increase with increasing electron pT. • The tagging efficiency of pure b-decay is small and almost constant. The data is in between, indicating that the b fraction increase with pT. Yield of (unlike – like) hadron per leading electron

  35. Result: b/(b+c) ratio as function of pT(e) (b max) and (c min) (b min) and (c min) (b max) and (c max) (b min) and (c max) FONLL: Fixed Order plus Next to Leading Log pQCD calculation

  36. Summary of e-h correlation analysis • be/(ce + be) has been studied in p+p collisions at √s =200GeV(RUN5) • Invariant mass distributions of simulation agree well with the data. • Experimental result is somewhat higher than FONLL calculation (almost consistent) Outlook • Extension of the analysis for higher pT (pT(e)>5 GeV/c) • RUN6 analysis for more statistics(~X3).

  37. Measurement of DK p p • Reconstruct D0K+p-p0 decay in pp • p0 identified via p0 gg decay • No charged hadron pid. • Advantages of D0K+p-p0 mode: • Relatively large BR (14.1%) • Can be triggered by p0 Direct Measurement: DKpp p+ p0 Trigger EMCal Trigger

  38. Invariant Mass Distribution • Year5 p+p s=200GeV data set is used • Observe 3s significant signal in pT D range 5 ÷ 15 GeV/c • No clear signal is seen for pT D < 5 GeV/c • The signal is undetectably small for pT D > 15 GeV/c Analysis by S. Butyk (LANL)

  39. Momentum Dependence • Observe clear peak in all pT bins from 5 GeV/c to 10 GeV/c • Fits are parabola + gaussian • Background is uniform within fitting range • Mass is systematically lower then PDG value  Trying to resolve by improving momentum and energy calibration

  40. Summary of DKpp analysis • Clear peak of D0 meson observed in Run5 p+p data in D0K+p-p0 decay channel • Signal statistic significantly enhanced by use of high momentum photon trigger • Signal is measurable in 5 to 15 GeV/c pT bins • Analysis is under way to determine invariant cross section for the production

  41. Summary • PHENIX has rich open heavy flavor measurement • Main work has done so far in single electron channel • Observation of strong suppression of heavy flavor electrons • Observation of large v2 of heavy flavor electrons • New analyses in pp • b/c measurement via e-h charge correlation • Single muon measurement • Direct observation of D K p p

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