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Non-Photonic Electron-Hadron Correlations at STAR and PHENIX

Non-Photonic Electron-Hadron Correlations at STAR and PHENIX. Bertrand Biritz University of California, Los Angeles. Outline. Motivation Analysis procedure Near-side contribution in p+p collisions Away-side broadness in A+A collisions Outlook.

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Non-Photonic Electron-Hadron Correlations at STAR and PHENIX

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  1. Non-Photonic Electron-Hadron Correlations at STAR and PHENIX Bertrand Biritz University of California, Los Angeles

  2. Outline • Motivation • Analysis procedure • Near-side contribution in p+p collisions • Away-side broadness in A+A collisions • Outlook

  3. Further supported by 3-particle correlations Motivations Conical Pattern in 2-Particle Correlations in Au+Au Collisions pTtrig= 2.5-4.0 GeV/c; pTasso = 1.0-2.5 GeV/c Conical Pattern Mark Horner (for STAR Collaboration): J. Phys. G: Nucl. Part. Phys. 34 (2007) S995 See STAR paper on 3-particle correlations at arXiv:0805.0622v2 (accepted by PRL)

  4. Near Side: what’s the contribution of B/D decay to the non-photonic electrons? trigger Motivations Conical Pattern in 2-Particle Correlations in Au+Au Collisions pTtrig= 2.5-4.0 GeV/c; pTasso = 1.0-2.5 GeV/c What if we trigger on non-photonic electrons? Mark Horner (for STAR Collaboration): J. Phys. G: Nucl. Part. Phys. 34 (2007) S995 Away Side in medium: How does B/D lose energy? Via conical emission?

  5. Study of heavy flavor via non-photonic electrons PYTHIA • D mesons have their directions well represented by the daughter electrons, above 1.5 GeV/c. • Electrons from B decays can represent the B meson momentum direction well if pT > 3 GeV/c.

  6. PHENIX central arm coverage: • || < 0.35 •  = 2 x π/2 • p > 0.2 GeV/c • typical vertex selection: |zvtx| < 20 cm • charged particle tracking using Drift Chamber (DC) and Pad Chamber 1 (PC1) • electron identification based on • Ring Imaging Cherenkov detector (RICH) • Electro-Magnetic Calorimeter (EMC) Electron ID with PHENIX Data Sample: At sNN = 200 GeV, p+p collisions in run5/6 (2006), Au+Au collisions in run7 (2007).

  7. Electron ID with STAR • TPC • || < 1.5 •  = 2π • p > 0.1 GeV/c • particle ID • BEMC/BSMD • PbSc • 20 X0 • energy and particle rejection: e and h Data Sample: At sNN = 200 GeV, p+p collisions in run5/6 (2006), d+Au collisions in run8 (2008),Cu+Cu collisions in run5 (2005), Au+Au collisions in run7 (2007). • Time Projection Chamber (TPC) • Barrel Electro-Magnetic Calorimeter (BEMC) • Barrel Shower Maximum Detector (BSMD)

  8. Decay photon conversions p0 → g g, g→ e+ e- in material Main background Dalitz decays p0 → ge+ e- Direct photon conversions Small but could be significant at high pT Heavy flavor electrons D/B → e± + X Weak Kaon decays Ke3: K± → p0e±e < 3% contribution in pT > 1 GeV/c Vector Meson Decays w, , fJ,  → e+e- < 2-3% contribution in all pT Electron signal and background Non-photonic electrons Photonic electrons

  9. PHENIX

  10. e+ (global track) (assigned as primary track) e- e- (primary track) dca  Identifying the Photonic Background • The invariant masses of the OS and SS e-pairs have different distributions. • Reconstructed photonic electrons are the result from subtracting SS from OS. • Photonic electrons are (reconstructed photonic electrons) / ε • ε is the background reconstruction efficiency calculated from simulations.

  11. Procedure to Extract the e-h Correlations All Tracks In case of low purity… Pass electron ID cuts Inclusive electrons Non-photonic electrons Photonic electrons Reco-photonic electrons = OppSign – combinatorics Not reco-photonic electrons = (1/ε-1)*(reco-photonic) – Δφhadron Semi-inclusive electrons Δφnon-pho = Δφsemi-incl + ΔφSameSign – (1/eff -1)*(ΔφOppSign – ΔφSameSign) Each element has its own corresponding Δφ histogram.

  12. Near-Side contribution in p+p

  13. Non-photonic e-h correlations in p+p 200GeV • Clear azim. correlation is observed around near and away side. • Fitting measured dn/dφ distribution from B and D decays, we can estimate B decay contribution to non-photonic electron. B D

  14. B contribution to non-photonic e in p+p 200GeV Almost fifty-fifty B and D contributions to non-photonic e’s at 5.5 < pT < 9 GeV/c and FONLL prediction is consistent with our data within errors.

  15. B contribution to non-photonic e in p+p 200GeV

  16. Large bottom quark energy loss? RAA for non-photonic electrons is consistent with hadron’s. This indicates a large energy loss for not only charm but also bottom quarks. non-γ e hadron With the measurements of r @ pp and RAA, we can derive a relationship between

  17. together with models • Dominant uncertainty is normalization in RAA analysis • ; B meson is also suppressed • prefer Dissociate (II) and • Resonance (III) model (large b energy loss) pT > 5 GeV/c STAR preliminary I: Djordjevic,Gyulassy, Vogt and Wicks,Phys. Lett. B 632 (2006) 81; dNg/dy = 1000 II: Adil and Vitev, Phys. Lett. B 649 (2007) 139 III: Hees, Mannarelli, Greco and Rapp,Phys. Rev. Lett. 100 (2008) 192301

  18. Non-photonic e-h correlations have been measured in p+p collisions to retrieve B and D contributions to non-photonic electrons up to pT~9 GeV/c. • Comparable B and D contributions for electron pT from 5.5~9 GeV/c. • FONLL prediction and the eB/(eB+eD) results are consistent with each other within errors. • The measured B/D ratio would imply considerable b quark energy loss in medium based on RAA measurement from central Au+Au collisions. One more measurement is needed: or r for A+A. Near-side Summary

  19. Away-side broadness in A+A p+p and d+Au collisions serve as a reference for the cold nuclear matter…

  20. 3 < pTtrig< 6 GeV/c & 0.15 < pTasso< 0.5 GeV/c Non-photonic e-h correlations in d+Au 200 GeV STAR Preliminary Non-photonic e-h azimuthal correlation is measured for π range, and open markers are reflections.The away-side correlation can be well described by PYTHIA calculations for p+p i.e. no medium effectsseen.

  21. about 40% non-flow or fluctuation (Gang Wang, Nucl. Phys. A 774 (2006) 515.) 0 – 20%: 3 < pTtrig< 6 GeV/c & 0.15 < pTasso< 0.5 GeV/c Non-photonic e-h correlations in Cu+Cu 200 GeV Upper limits of v2 used are 60% of hadron v2 values measured with the v2{EP} method (equivalent to v2{2}). On the away side, there’s a broad structure or a possible double-hump feature, even before v2 subtraction. PYTHIA fit has a big χ2.

  22. Possible interpretations The away side in e-h is similar to what has been observed in h-h correlations, and consistent with Mach Cone calculations etc. The charm jet deflection provides an alternative interpretation.

  23. 0 – 20%: 3 < pTtrig< 6 GeV/c & 0.15 < pTasso< 0.5 GeV/c Non-photonic e-h correlations in Au+Au 200 GeV STAR Preliminary Upper limits of v2 used are 80% of hadronv2 values measured with the v2{EP} method. Non-photonic e-h correlation is broadened on the away side. PYTHIA fit has a big χ2.

  24. Using the d+Au collision as a reference, the shape of non-photonic e-h azimuthal correlation function is found to be modified in central Cu+Cu and Au+Au collisions due to the presence of the dense medium created in these collisions. • Away-side: Hint of a broad structure, similar shape to that from h-h correlations. • Induced by heavy quark interaction with the dense medium? • Quantitative measure and investigation of the nature of the possible conical emission pattern will require more statistics. DAQ1000 will help us there. Should also try 3-particle correlations. Away-side Summary

  25. Thank you

  26. Back up slides

  27.    HQ Production Mechanism    flavor creation • Due to large mass, HQ productions are considered as point-like pQCD processes • HQ is produced at the initial via leading gluon fusion, and sensitive to the gluon PDF • NLO pQCD diagrams show that Q-Qbar could be not back-to-back in transverse plane • We need to study this smearing effect with models   0 gluon splitting

  28. PYTHIA simulations B Each pt bin is weighted with their relative yields, and then they are summed up. For each pt bin, the non-photonic e-h correlations B_corr and D_corr are combined according to B’s and D’s relative contributions to the non-photonic electrons: (eB*B_corr + eD*D_corr) / (eB+eD) D

  29. PuritydAu, CuCu, AuAu: above 98% for 3 < pT < 6 GeV/cp+p collisions: above 98% for 3 < pT < 6 GeV/c; 80% for 9 GeV/c. Electron ID in STAR calibrated Log(dE/dx) With BEMC and BSMD, the electron peak is enhanced in the energy loss distribution, and we obtain a very pure electron sample.

  30. 3 < pTtrig < 6 GeV/c & 0.15 < pTasso < 0.5 GeV/c PYTHIA simulations weighted with CuCu yields B D Here we assume the B/D contribution in CuCu is similar to that in p+p. Even if they are not similar, we don’t expect the double-hump without a medium.

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