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Open Heavy Flavor in Heavy Ion Collisions

Open Heavy Flavor in Heavy Ion Collisions. James C. Dunlop Brookhaven National Laboratory. Motivation: Grey Probes. Wicks et al, Nucl. Phys. A784 (2007) 426. Problem: interaction with the medium so strong that information lost: “Black”

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Open Heavy Flavor in Heavy Ion Collisions

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  1. Open Heavy Flavor in Heavy Ion Collisions James C. Dunlop Brookhaven National Laboratory J.C. Dunlop, QM2009

  2. Motivation: Grey Probes Wicks et al, Nucl. Phys. A784 (2007) 426 • Problem: interaction with the medium so strong that information lost: “Black” • Significant differences between predicted RAA, depending on the probe • Experimental possibility: recover sensitivity to properties of the medium by varying probe BNL Colloquium James Dunlop

  3. Charm/Beauty: No shade of gray STAR STAR, PRL 98 (2007) 192301 PHENIX, PRL 98 (2007) 172301 • Unexpectedly strong suppression of non-photonic electrons • Tool to study mechanism of energy loss BNL Colloquium James Dunlop

  4. + e- K- e D0 D*0 B- b b B+ D0 - K+ Measurement: a wealth of decay • 4 pages D0, 10 pages of B+ decay modes in PDB • Most promising modes: • Leptons: B.R. ~10% per lepton species of B and D • Electrons: triggerable in calorimeters • Muons: no Bremsstrahlung, photonic background • Neither have full kinematic reconstuction • Pure hadronic: full kinematics • D➝Kπ, D*➝Kππ • Not easily triggerable • B➝J/Ψ + X • Clean from D contamination • B.R. ~1%, triggerable J.C. Dunlop, QM2009

  5. Non-photonic electrons in p+p: the baseline STAR, PRL 98 (2007) 192301 • Factor ~2 discrepancy between STAR and PHENIX • How to resolve this? J.C. Dunlop, QM2009

  6. Open Charm Cross-section Poster F. Jin • STAR: • D0, electrons • PRL 94(2005) 062301 • D0, muons • arXiv:0805.0364 • PHENIX: • Single electrons • PRL 97(2006) 252002 • Electron pairs • 544 ± 39(stat) ± 142 (syst) ± 200 (model) • PLB 670 (2009) 313 • Large discrepancy between extracted total cross-section from STAR and PHENIX • Large theoretical uncertainties J.C. Dunlop, QM2009

  7. PHENIX: Extrapolation issues Point not used in extrapolation PHENIX: PRL 97 (2006)252002 FONLL: arXiv:0709.252301 Single electrons: FONLL shape to extrapolate x1.8 Quoted error: 10% Dileptons: PYTHIA to convert and extrapolate Quoted error: 33% Measured region Even worse: Additional x2 uncertainty in σ beyond FONLL Uncertainty driven by low pT,where theory poorly constrained J.C. Dunlop, QM2009

  8. STAR: Minimal Extrapolation STAR: PRL 94(2005) 062301 STAR:arXiv:0805.0364 • STAR: dominated by muons,pT ~0.17-0.21 GeV/c, and direct reconstruction of D0 which fall less steeply • Total extrapolation 10%: not the dominant uncertainty J.C. Dunlop, QM2009

  9. But extrapolation isn’t the issue at high pT STAR STAR, PRL 98 (2007) 192301 • Cross section dominated by low pT, theory not well constrained • High pT not extrapolated AND theory better constrained J.C. Dunlop, QM2009

  10. Main difference: material See poster, S. Lapointe • PHENIX: low material, so low conversion background • New detectors are changing this • STAR: before run 8, Silicon Vertexing detectors • Reduces background for D, but increases background for electrons • Reconstruct conversion background, so in principle not an issue, but… • Decision: remove until higher precision silicon can be built STAR Preliminary J.C. Dunlop, QM2009

  11. STAR Preliminary Beam pipe + SVT + SSD+ Dalitz Count Beam pipe + Dalitz TPC Inner Field cage STAR: status of low material run Inclusive e/π ratio Run-3 and Run-8 Run-3 Run-8 R [cm] Material in front of TPC reduced by an order of magnitude The final results are not ready in time for this conference Analysis status Fu Jin & Xin Li, poster presentations Jörn Putschke for the STAR Collaboration, QM09, Knoxville

  12. But electrons won’t answer the question B. Biritz, 5D A. Dion, 5D Even when we resolve discrepancy in electrons: Both charm and beauty contribute in an unpredicted way Quenching can, hopefully will, change eB/eD J/Ψ are important, according to PHENIX What is the RAA of high pT J/Ψ? 1/3 of e from J/Ψ decays! 9 1 pT [GeV/C] J.C. Dunlop, QM2009

  13. Towards eB/eD B. Biritz, 6D Until we have precise vertexing: correlation measurements provide constraints Exclude original radiative calc. 9 1 pT [GeV/C] PHENIX, arXiv:0903.4851 J.C. Dunlop, QM2009

  14. J/Ψ Feeddown into electrons D. Kikola, 2D E. Atomssa, 2D • PHENIX: J/Ψ➔e ~1/3 of non-photonic electrons for pT>5 GeV • Large uncertainties for both STAR and PHENIX at high pT • At face value, consistent within uncertainties • Expect large improvements (x5) in STAR statistics runs 9 and 10 • Uncertainties further complicate the interpretation of electrons J.C. Dunlop, QM2009

  15. STAR Preliminary The other way: B feeddown into J/Ψ D. Kikola, 2D C. Perkins, 1D • B→J/Ψ the “golden channel” for B with vertex detectors • Until we have precision vertexing, constrained by correlations • STAR p+p: B→J/Ψ/All J/Ψ (13 ± 5)%, in agreement with CDF at this pT • Model dependence: depends on tuned PYTHIA p+p d+Au J.C. Dunlop, QM2009

  16. Other correlations T. Engelmore, 6D B. Biritz, 6D • Electron-muon: low backgrounds • Electron-hadron in heavy systems: away-side modification? • Proof-of-principle, await higher statistics, better background rejection for conclusion J.C. Dunlop, QM2009

  17. Outlook: Precision Vertexing STAR Heavy Flavor Tracker VTX Entering prime years for heavy flavor with precision vertexing Complementary capabilities and systems ALICE: LHC, where c becomes a “light” quark PHENIX: Focus on electrons and muons STAR: Focus on fully reconstructed kinematics J.C. Dunlop, QM2009

  18. The “simple”: eB vs. eC A. Dainese, 5D PHENIX Projection Expected with VTX (0.4/nb) • At ALICE, c a “light quark”, eB/eC sensitive to B energy loss • Main focus of PHENIX VTX: isolation of eB from eD • Expected DCA resolution ~50 μm, STAR SVT had achieved ~200 μm • Warning: cτ of D+~ cτ of B and what matters is βγcτ • More discriminating: multi-hadron correlations, mB>>mD,or B→J/Ψ J.C. Dunlop, QM2009

  19. The other lepton: muons A. Dion, 5D PHENIX Projection with FVTX • Muons an independent check BUT limited by systematics • PHENIX FVTX to reduce backgrounds • ALICE: muon detectors with clean B signal, pT<~20 GeV/c • STAR studying upgrade: mid-rapidity Muon Telescope Detector J.C. Dunlop, QM2009

  20. The harder: direct reconstruction STAR RAA D+ Kpp A. Dainese, 5D Poster, J. Bouchet • Direct reconstruction with full kinematic information • Only possible for charm: • D+, D0, Λc • No ambiguities D0 B  e + X mC = 1.2 GeV mC = 0 Λc J.C. Dunlop, QM2009

  21. Charm Elliptic Flow STAR A. Dion, 5D STAR Projection Current measurements: large elliptic flow of electrons • Ambiguities: B vs D fraction, decay kinematics • Are electrons even in the pT region where hydro is applicable? Solution: direct reconstruction at low pT e D0 J.C. Dunlop, QM2009

  22. Summary • Current open heavy flavor measurements • Total cross-section: need to measure where the yield is • Non-photonic electrons: ongoing program to increase precision, decrease systematics, and resolve the STAR/PHENIX discrepancy • Correlations to constrain contribution of charm • J/Ψ may affect B, and B may affect J/Ψ • Future: entering the age of precision vertex detectors • Separate charm and beauty contributions to electrons • Direct reconstruction of charm • Elliptic flow: need to measure where hydro is J.C. Dunlop, QM2009

  23. + c g e- K- g c e D0 D*0 B- c c b g b g B+ D0 g g - K+ Heavy Flavor Correlations Isolate b from c Isolate production mechanism In medium: what is losing energy, and how much? Flavor creation  gluon splitting/fragmentation 0 BNL Colloquium James Dunlop

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