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Heavy Flavor Physics in HI at PHENIX

Heavy Flavor Physics in HI at PHENIX. Rachid Nouicer, BNL. Charmonia Suppression in A+A Collisions Cold Nuclear Matter Effects Summary and Outlook. R elativistic H eavy I on C ollider ( RHIC ). PHOBOS. BRAHMS. RHIC. PHENIX. STAR. AGS. TANDEMS.

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Heavy Flavor Physics in HI at PHENIX

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  1. Heavy Flavor Physics in HI at PHENIX Rachid Nouicer, BNL • Charmonia Suppression in A+A Collisions • Cold Nuclear Matter Effects • Summary and Outlook

  2. RelativisticHeavyIonCollider (RHIC) PHOBOS BRAHMS RHIC PHENIX STAR AGS TANDEMS -2 concentric rings of 1740 superconducting magnets - 3.8 km circumference Energies: 7-200 GeV (AA) 48-500 GeV (pp) (Proton-Proton) (Au-deuteron) (Au-Au, Cu-Cu) (U-U, Cu-Au)

  3. Motivation: Discoveries We’ve created at strongly-coupled QCD matter at high temperature and energy density with partonic collectivity v2(KET,nq) v2(pT,m) RAA(pT)=(spec)AA/(spec)pp Quark Energy-Loss: perturbative QCD (gluon radiation) Collective Expansion: ideal hydrodynamics (QGP equation-of-state) Hadronization: quark coalescence rapid thermalization, “perfect liquid”  strongly-interacting QGP

  4. e time g space VNI Simulation Schematic Time Evolution p p K f p jet J/Y Freeze-out Hadronization  Expansion ----------- QGP? Thermalization? Hard Scattering Au Au

  5. Why is Heavy Flavor Interesting? Matsui and Satz, Plys. Lett. B 178 (1986) 416 Debye screening predicted to destroy J/y (1S: cc) in QGP with other sates “melting” at different temperatures due to different sizes or binding energies. Probe deeper into the medium: Energy loss of heavy quarks • Dead-cone effect: gluon radiation suppressed at small angles (q < mQ/EQ) Radiative energy loss S. Wicks et al. Nucl. Phys. A784 (2007) 426 M. Djordjeevic et al.Nucl. Phys. A733 (2004) 265 Energy loss: Eg > ELQ > EHQ

  6. Heavy Quarks as Probe of QGP • p+p data: →baseline of heavy ion measurements →test of pQCD calculation: mc ~ 1.3 GeV, mb ~ 4.8 GeV >> Tc , ΛQCD less affected than light quarks • Due to their large mass heavy quarks are primarily produced by gluon fusion in early stage of collision. production rates calculable by pQCD (M. Gyulassy and Z. Lin, PRC 51, 2177 (1995) → • d+Au data: -assess initial state effects cold nuclear matter effects Gluon shadowing, initial energy loss, Cronin effect → → • Heavy ion data:- they travel through the created medium interacting with its constituentsStudying energy loss of heavy quarks independent way to extract propertiesof the medium. →

  7. Heavy Flavor Measurements 1) Direct:ideal but very challenging - reconstruction of all decay products e.g. D0 K-p+ (B.R.: 3.8 %) Indirect measurement Direct measurement Charm: Mc ≈ 1.5 GeV Bottom: Mb ≈ 4.75 GeV 2) Indirect (Alternative):heavy flavor semi leptonic decays contribute to single lepton and lepton pair spectra • Open heavy flavor charm (and beauty) via electrons charm (and beauty) via muons c  e+ + anything(B.R.: 9.6%) b  e+ + anything(B.R.: 10.9%) c  + + anything (B.R.: 9.5%)

  8. Measuring Heavy Flavor at PHENIX Central Arms detect electrons • |η| < 0.35 and 2 x p/2 in azimuth • pe > 0.2 GeV/c • Electron identification: - Ring Imaging Cerenkov detector - Electromagnetic Calorimeter • Silicon Vertex Tracker (VTX): - new detector installed in 2011 - measure displaced vertices of electrons at central rapidity to separate c e from b e Forward Arms detect muons • 1.2 < |η| < 2.4 and -2.2 < |η| < -1.2 • Muon Tracker reconstructs trajectories and determines momentum • Muon magnets and Muon Identifier steel absorb hadrons, pion rejection e+ e- → →

  9. Extraction of Heavy Flavor Signal • Electron: measuring first inclusive electrons: - Background subtracted method: using background cocktail composed of electron sources measured at PHENIX: photonic and non-photonic sources: Conversion of photons from hadron decays in material Dalitz decays of light mesons (p0, h, w, h’, f)Ke3 : K±  p0 e± ve vector meson decays: r, w, f  e+ e- heavy quarkonia decay - Converter subtract method:adds material of known thickness around beam pipe, measures conversion electrons by extra yield produced. Used at lower pT. Both cocktail and converter methods agree • Muon: measuring first inclusive muons: - Background subtracted method: backround removed trough hadronic cocktail subtraction. Backgrounds include: - decay muons: resulting from light hadron decay. - Punchtrough hadrons: hadrons that are not absorbed in steel absorber, look identical to muons.

  10. Open Heavy Flavor (c,b) via 1) single electrons (at mid-rapidity)2) single muons (at forward/backward rapidity) e (or m)

  11. Open Heavy Flavor Measurement in p + p Collisions PRL 97, 252002 (2006) Single electrons (|y| < 0.35) PRD 76, 09002 (2007) Single muons (1.4 < y < 1.9) p + p • Mid-rapidity, eHF yield is in agreement with pQCD (FONLL) calculations • Forward rapidity, mHF slightly higher that expected FONLL calculations

  12. Open Heavy Flavor Measurement in p + p Collisions PRL 97, 252002 (2006) Single electrons (|y| < 0.35) PRD 76, 09002 (2007) Single muons (1.4 < y < 1.9) p + p • Low pT HF lepton spectra is dominated by charm. So we simply extrapolate to pT = 0 GeV/c using FONLL to get charm cross section

  13. Cross Section: Open Heavy Flavor in p + p Collisions PHENIX: PRCarXiv:1204.0754 Agreement with FONLL within uncertainties.

  14. Open Heavy Flavor (eHF) Measurement in Au+Au Collisions PRL 98, 172301 (2007) • Same method as in p + p • Heavy flavor electrons from Au + Au • Compared to Ncoll scaled p + p (FONLL x 1.71) Nuclear modification factor <Nbinary>/inelp+p (Nuclear Geometry) RAA = 1 → no overall effect RAA < 1 → suppression RAA > 1 → enhancement

  15. Quantifying Medium Effects: eHF Nuclear modification factor • Heavy quarks suppressed the same as light quarks, and they flow, but less. • Collective behavior is apparent in eHF; but it is lower than v2 of  p0 for pT > 2 GeV/c. R. Nouicer arXiv:0901.0910 [nucl-ex] • This contradicts models that assumed only inelastic (radiative) in-medium energy loss, which predicted that RAA(HQ) > RAA(light quark) due to “dead cone effect”. • Separating D and B meson contributions key for establishing mass hierarchy in understanding energy loss.

  16. Open Heavy Flavor eHF in d+Au system d d Au • In peripheral d+Au collisions production expected to be similar to p+p. Consistent withunity within uncertainties. • Central d+Au indicates slight enhancement, similar to Cronin effect in hadron production. • Absence of CNM effects at mid-rapidity in d+Au system. • Large eHF suppression observedin Au+Au collisions can safely be attributed only to final state (hot nuclear matter) effects. d Au d 16

  17. Open Heavy Flavor eHF System Size Dependence:Au+Au vs Cu+Cu at 200 GeV Comparison of central Cu+Cu with semi-peripheral Au+Au at the same energy, 200 GeV, shows good agreement. Ncoll(CuCu) = 150 Ncoll(AuAu) = 91 Npart(CuCu) = 86 Npart(AuAu) = 62 No suppression is observed

  18. Open Heavy Flavor eHF System Size Dependence:Au+Au vs Cu+Cu vs d+Au at 200 GeV Ncoll Ncoll RAA consistent across systems as a function of centrality for d+Au, Cu+Cu and Au+Au at the same energy, 200 GeV.

  19. Open Heavy Flavor in Cu+Cu at 200 GeV Single electrons eHF vs single muons mHF Mid-rapidity vs forward rapidity Suppression is stronger at forward rapidity than mid-rapidity- why ? • Data in agreement with I. Vitev’s prediction that accounts for: • for final state energy loss effectswith his dissociation model • cold nuclear matter effects,such as nuclear shadowing andparton multiple scattering Indication of Cold Nuclear Matter (CMN) effects at forward rapidity in Cu+Cu system at 200 GeV

  20. The open charm spectra discussed in previous slides serve as baseline for charmonium J/y

  21. Di-leptons in p+p at 200 GeV Di-eHF: Midrapidity |y|<0.35 Di- mHF: Forward Rapidity 1.2 < |y| <2.2 PHENIX has excellent capabilities of measuring different quarkonia states in di-electron and di-muon channels.

  22. J/ψ Production at p+p at 200 GeV arXiv: 1105.1966v1 PRL 98, 232002 (2007) Total J/ψ cross-section : 181 +/- 22 nb (stat. + sys.)

  23. Open Heavy Flavor eHF in Au+Au at 200 GeV Mid-rapidity (eHF) vs forward rapidity (mHF) arXiv: 1103:6269 Suppression is stronger at forward rapidity than mid-rapidity- why (CNM) ? SPS: NA50, 17.2 GeV Suppression in mid-rapidity is comparable to that measured at SPS energies. No obvious pattern of the suppression with energy density.

  24. What are the CNM effects that are contributing in J/y production? d Au J/y in d+Au  CNM thickness dependence CNM effects appear to provide a large fraction of the observed suppression based on these models. eHF : |y| <0.35 mHF : |y| Reasonable agreement withEPS90model for central but not peripheral CGC calculations can’t reproduce mid-rapidity(Nucl. Phys. A 770(2006) 40). EPS90with linear thickness dependence fails to describe centrality dependence of forward rapidity region.

  25. What Next? Nuclear modification factor B+D-mesons via single electrons (NPE) Ralf F. Rapp Elliptic Flow Ralf F. Rapp Ralf F. Rapp • Separating D and B meson contributions key for establishing mass hierarchy in understanding energy loss… D  eHF + Xand B  eHF + X Nuclear modification factor

  26. e Life time (ct) D0 : 123 mm B0 : 464 mm Layer 4 DCA Layer 3 D p Layer 2 p B Layer 1 e Barrel 4 Barrel 3 Barrel 2 Barrel 1 Barrel 1 Barrel 2 Barrel 3 Barrel 4 D  eHF and B  eHF with PHENIX Silicon Vertex Tracker (VTX) Installed in 2010 data in Run-11 and 12 To understand these medium effects in more detail it is imperative to directly measure the nuclear modification and flow of D- and B-mesons independently (c  eHF and b  eHF).

  27. PHENIX-VTX at RHIC: Display of Single Event VTXRUN-12: p+p at 200 GeV VTXRUN-11: Au+Au at 200 GeV Primary vertex single event Beam size Primary Vertex: BBC vs VTX Data: AuAu at 200 GeV Data: AuAu 200 GeV Data: AuAu 200 GeV

  28. Performance Plot: Extracting b and c Signals Electron DCA vs Charged Hadron DCA • DCA distributions of electrons are broader than that of all charged • The difference can be due to heavy flavor signal • Large DCA tail: Can it be b-signal? • Needs comparison with expected shape from MC

  29. Summary • In p+p collisions, eHF yields have been measured and agree with pQCD calculations (FONLL) • Open Heavy Flavor shows medium effects similar to those light hadrons in central Au+Au collisions • Initial states effects do not appear to explain eHF suppression in Au+ Au • consistent with creation of a very dense and strongly interacting deconfined medium • However, initial state effects apparent at forward rapidity • Recent Cu+Cu and d+Au measurements indicate additional sizable cold nuclear matter effects in different kinematic regions. • New PHENIX-VTX detector open new era to make precise measurements of open heavy Flavor: separating D and B meson contributions key for establishing mass hierarchy in understanding energy loss…

  30. Outlook PHENIX Forward Vertex Detector (FVTX) • Design to measure displaced vertices of muons detected by PHENIX muon detectors VTX FVTX • Two detectors are forward and backward rapidity with 4 stations each, covering 1.2 < |h| < 2.4 and 2p in azimuth (f). • Commissioned in Run-12.

  31. Auxiliary Slides 9/21/2014 rachid.nouicer@bnl.gov

  32. Theory: D  eHF and B  eHF QCD Predictions for Charm and Bottom Quark Production at RHIC Matteo Cacciari et al. PRL 95 (2005) 122001

  33. Nuclear modification factor B+D-mesons via single electrons (NPE) Ralf F. Rapp Motivation: Theoretical Calculations for HF • Ralf F. Rapp, private communication To be published by Ralf F. Rapp et al. Realistic hydro (fit to multistrange and bulk particles) with heavy-quark diffusionin the QGP, hadronization via resonance recombination/fragmentation, followed by hadronic diffusion. There is no tuning of the HQ physics. Elliptic flow B+D-mesons via single electrons (NPE) Ralf F. Rapp

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