Open Heavy Flavor in Heavy Ion Collisions James C. Dunlop Brookhaven National Laboratory 04/02/ J.C. Dunlop, QM2009

10/30/2007BNL Colloquium James Dunlop 2 Motivation: Grey Probes Problem: interaction with the medium so strong that information lost: “Black” Significant differences between predicted R AA, depending on the probe Experimental possibility: recover sensitivity to properties of the medium by varying probe Wicks et al, Nucl. Phys. A784 (2007) 426

10/30/2007BNL Colloquium James Dunlop 3 Charm/Beauty: No shade of gray Unexpectedly strong suppression of non-photonic electrons Tool to study mechanism of energy loss STAR, PRL 98 (2007) PHENIX, PRL 98 (2007) STAR

Measurement: a wealth of decay 4 pages D 0, 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/  + X Clean from D contamination B.R. ~1%, triggerable 04/02/2009J.C. Dunlop, QM K-K- b b B-B- D *0 D0D0 ++ e e-e- B+B+ -- K+K+ D0D0

Non-photonic electrons in p+p: the baseline Factor ~2 discrepancy between STAR and PHENIX How to resolve this? 04/02/2009J.C. Dunlop, QM STAR, PRL 98 (2007)

Open Charm Cross-section 04/02/2009J.C. Dunlop, QM Large discrepancy between extracted total cross-section from STAR and PHENIX Large theoretical uncertainties STAR: D 0, electrons PRL 94(2005) D 0, muons arXiv: PHENIX: Single electrons PRL 97(2006) Electron pairs 544 ± 39(stat) ± 142 (syst) ± 200 (model) PLB 670 (2009) 313 Poster F. Jin

PHENIX: Extrapolation issues 04/02/2009J.C. Dunlop, QM Even worse: Additional x2 uncertainty in σ beyond FONLL Uncertainty driven by low p T, where theory poorly constrained Single electrons: FONLL shape to extrapolate x1.8 Quoted error: 10% Dileptons: PYTHIA to convert and extrapolate Quoted error: 33% Measured region Point not used in extrapolation PHENIX: PRL 97 (2006) FONLL: arXiv:

STAR: Minimal Extrapolation STAR: dominated by muons,p T ~ GeV/c, and direct reconstruction of D 0 which fall less steeply Total extrapolation 10%: not the dominant uncertainty 04/02/2009J.C. Dunlop, QM STAR:arXiv: STAR: PRL 94(2005)

STAR But extrapolation isn’t the issue at high p T Cross section dominated by low p T, theory not well constrained High p T not extrapolated AND theory better constrained 04/02/2009J.C. Dunlop, QM STAR, PRL 98 (2007)

Main difference: material 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 04/02/2009J.C. Dunlop, QM See poster, S. Lapointe STAR Preliminary

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

But electrons won’t answer the question Even when we resolve discrepancy in electrons: Both charm and beauty contribute in an unpredicted way Quenching can, hopefully will, change e B /e D J/Ψ are important, according to PHENIX What is the R AA of high p T J/Ψ? 04/02/2009J.C. Dunlop, QM A. Dion, 5D 1/3 of e from J/Ψ decays! p T [GeV/C] 1 9 B. Biritz, 5D

Towards e B /e D Until we have precise vertexing: correlation measurements provide constraints Exclude original radiative calc. 04/02/2009J.C. Dunlop, QM p T [GeV/C] 1 9 B. Biritz, 6D PHENIX, arXiv:

J/Ψ Feeddown into electrons PHENIX: J/Ψ ➔ e ~1/3 of non-photonic electrons for p T >5 GeV Large uncertainties for both STAR and PHENIX at high p T –At face value, consistent within uncertainties –Expect large improvements (x5) in STAR statistics runs 9 and 10 Uncertainties further complicate the interpretation of electrons 04/02/2009J.C. Dunlop, QM D. Kikola, 2DE. Atomssa, 2D

The other way: B feeddown into J/Ψ 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 p T –Model dependence: depends on tuned PYTHIA 04/02/2009J.C. Dunlop, QM STAR Preliminary d+Au D. Kikola, 2DC. Perkins, 1D p+p

Other correlations Electron-muon: low backgrounds Electron-hadron in heavy systems: away-side modification? Proof-of-principle, await higher statistics, better background rejection for conclusion 04/02/2009J.C. Dunlop, QM T. Engelmore, 6D B. Biritz, 6D

Outlook: Precision Vertexing 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 04/02/2009J.C. Dunlop, QM STAR Heavy Flavor Tracker VTX

The “simple”: e B vs. e C At ALICE, c a “light quark”, e B /e C sensitive to B energy loss Main focus of PHENIX VTX: isolation of e B from e D –Expected DCA resolution ~50 μm, STAR SVT had achieved ~200 μm Warning: c  of D + ~ c  of B and what matters is  c  –More discriminating: multi-hadron correlations, m B >>m D, or B→J/Ψ 04/02/2009J.C. Dunlop, QM A. Dainese, 5D Expected with VTX (0.4/nb) PHENIX Projection

The other lepton: muons Muons an independent check BUT limited by systematics –PHENIX FVTX to reduce backgrounds ALICE: muon detectors with clean B signal, p T <~20 GeV/c STAR studying upgrade: mid-rapidity Muon Telescope Detector 04/02/2009J.C. Dunlop, QM A. Dion, 5DPHENIX Projection with FVTX

The harder: direct reconstruction Direct reconstruction with full kinematic information Only possible for charm: –D +, D 0, Λ c No ambiguities 04/02/2009J.C. Dunlop, QM B  e + X R AA D +  K  m C = 1.2 GeV m C = 0 STAR A. Dainese, 5D D0D0 Poster, J. Bouchet ΛcΛc

Charm Elliptic Flow Current measurements: large elliptic flow of electrons Ambiguities: B vs D fraction, decay kinematics Are electrons even in the p T region where hydro is applicable? Solution: direct reconstruction at low p T 04/02/2009J.C. Dunlop, QM STAR A. Dion, 5D STAR Projection D0D0 e

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 04/02/2009J.C. Dunlop, QM

10/30/2007BNL Colloquium James Dunlop 23 Heavy Flavor Correlations Isolate b from c Isolate production mechanism In medium: what is losing energy, and how much? K-K- b b B-B- D *0 D0D0 ++ e e-e- B+B+ -- K+K+ D0D0 c c g g gluon splitting/fragmentation g g g g c c  0  Flavor creation