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Heavy-Flavour Production in Nucleus-Nucleus Collisions: From RHIC to LHC

Heavy-Flavour Production in Nucleus-Nucleus Collisions: From RHIC to LHC. Andr é Mischke. ERC-Starting Independent Research Group QGP - Utrecht. Hirschegg 2010 Strongly Interacting Matter under Extreme Conditions

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Heavy-Flavour Production in Nucleus-Nucleus Collisions: From RHIC to LHC

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  1. Heavy-Flavour Production in Nucleus-Nucleus Collisions: From RHIC to LHC André Mischke ERC-Starting Independent Research Group QGP - Utrecht Hirschegg 2010 Strongly Interacting Matter under Extreme Conditions 38nd International Workshop on Gross Properties of Nuclei and Nuclear ExcitationsHirschegg, Kleinwalsertal, Austria, January 17 - 23, 2010

  2. Outline • Introduction • - heavy-flavour production and energy loss in QCD matter • Total charm production cross section • Nuclear modification factor • Heavy-flavour azimuthal correlations • Summary I will not talk about collectivity and Quarkonia Andre Mischke (UU)

  3. Probing hot and dense QCD matter Quark-Gluon Plasma p+p collision Au+Au collision after the collision • Simplest way to establish the properties of a system • calibrated probe • calibrated interaction • suppression pattern tells about density profile • Heavy-ion collisions • hard processes serve as calibrated probe (pQCD) • traversing through the medium and interact strongly • suppression provides density measure • General picture: energy loss via medium induced gluon radiation (Bremsstrahlung) Nuclear modification factor: Andre Mischke (UU)

  4. Light hadron spectra at RHIC photons K.J. Eskola et al., Nucl. Phys. A747 (2005) 511 light charged hadrons,neutral pions central RAA data increasing density • Strong suppression in central Au+Au collisions • Suppression well described by energy loss models • Medium density 30-50 times normal nuclear matter • Surface bias effectively leads to saturation of RAA with density • Limited sensitivity to the region of highest energy density

  5. Heavy quark production Charm, PYTHIA 6.208 “Thermalizationof QGP” Hadronisation Quarkonia meltsand flow develops ~0.1 ~1 ~10 1015 Parton energy loss time scale (fm) Heavy-flavour production ~ h/2mQ • Primarily produced by gluon fusion in early stage of collision: production rates calculable in pQCD • Sensitivity to initial state gluon distribution M. Gyulassy and Z. Lin, Phys. Rev. C51, 2177 (1995) • Heavy quarks provide information about the hottest initial phase of the collision • Higher penetrating power: mQ>> Tc, QCD

  6. Energy loss of heavy quarks hot and dense medium parton • Probe deeper into the medium • Dead-cone effect: gluon radiation suppressed at small angles (q < mQ/EQ)Dokshitzer & Kharzeev, PLB 519, 199 (2001), hep-ph/0106202 • Less energy loss: Eg > ELQ > EHQ Wicks et al, NPA784, 426 (2007) Bottom Charm Gluon radiation probability: Andre Mischke (UU)

  7. Semileptonic decay of charm and bottom mesons first evidence for heavy-flavour particles F.W. Buesser et al. (CCRS), Nucl. Phys. B113, 189 (1976) robust electron trigger needs handle on photonic background Full reconstruction of open charmed mesons direct clean probe: signal in invariant mass distribution difficulty: large combinatorial background; especially in a high multiplicity environment event-mixing and/or vertex tracker needed Detection of heavy-flavour particles single or non-photonic electron Andre Mischke (UU)

  8. Single electron spectra Phys. Rev. Lett. 98 (2007) 192301 Phys. Rev. Lett. 98, 172301 (2007) Au+Au Au+Au 0-5% 10-40% 40-80% d+Au p+p p+p • Spectra measured up to 10 GeV/c • Integrated yield follows binary collision scaling • Yield strongly suppressed at high pT for central Au+Au Andre Mischke (UU)

  9. D0 reconstruction in STAR Cu+Cu 200 GeV A. Shabetai, QM 2008 d+Au 200 GeV PRL 94 (2005) 062301 Au+Au 200 GeV arXiv:0805.0364 [nucl-ex] • First identified open charmed mesons in heavy-ion collisions • Current measurements limited to low-pT Andre Mischke (UU)

  10. Charm cross section in STAR Use all possible signals - D0 mesons - electrons - muons Charm cross section is well constrained - 90% of total cross section - direct measurement - D0 mesons and muons constrain the low-pT region D0 muon electron Andre Mischke (UU)

  11. Di-electron measurement in PHENIX c dominant b dominant after subtraction of cocktail Phys. Lett. B670, 313 (2009) • “Cocktail” of backgrounds constructed from measured background sources • Comparison to charm, bottom and Drell-Yan from PYTHIA • In good agreement with single electrons (PRL 103, 082002 (2009)) scc= 518 ± 47(stat) ± 135(sys) ± 190(model) mb sbb= 3.9 ± 2.4(stat) +3/-2(sys) mb Andre Mischke (UU)

  12. Inclusive charm production cross section x4.5 x2 R. Vogt, Eur. Phys. J. Spec. Topic 155, 213 (2008) • Factor ~2 difference between STAR and PHENIX; but consistency with NLO pQCD (large uncertainties; primarily from scale choice and parton density functions) • Checks • - removal of silicon vertex detectors (STAR) • - better control over background contributions (PHENIX): 1/3 of single electrons are from J/ decays for pT > 5 GeV/c  up to 16% decrease in open heavy • Cross section follows binary collision scaling Andre Mischke (UU)

  13. Open-charmed meson spectra from CDF pp@ 1.96 TeV 5.8 pb-1 ¯ • Deviation of 50-100% at moderate and high-pT, but consistent within errors • Theoretically not fully understood …even in pp collisions Andre Mischke (UU)

  14. Charm production cross section (cont’d) NLO pQCD, CTEQ6M parton densities R. Vogt, private communication, 2009 LHC: 7-10 TeV • Large uncertainties  more data needed to constrain model parameters • Parton spectra from pQCD input for energy loss models Andre Mischke (UU)

  15. Charm cross section in ALICE • First promising decay channels • D*  D0s, D0 K, D+ K-++ • D,B  e + X • ALICE has the capability to measure open charm down to pT = 0 in pp and p-Pb (1 GeV/c in Pb-Pb) • ITS: impact parameter resolution better than 50mm for pT > 1.5 GeV/c Andre Mischke (UU)

  16. c g 0 g MC@NLOLO PYTHIA cbar  like-sign e-K pairs flavor creation (LO) gluon splitting (NLO) 3 < pT < 7 GeV/c c cbar g g g g NLO processes: gluon splitting A. M., PLB 671, 361 (2009) • e-D0 correlations at 200 GeV • away-side peak: Good agreement of peak shape between LO PYTHIA and MC@NLO • near-side: small gluon splitting contribution (6.5%) • Gluon splitting rate at RHIC consistent with MC@NLO LHC ? MC@NLO Gluon jet energy (GeV) Andre Mischke (UU)

  17. D* - jet azimuthal correlations at LHC Full Pythia simulation, pp@10 TeV jet axis D*  candidates  background ☐ signal 300k jets, <Ejet> ~ 30 GeV gluon splitting(z < ~0.5) gluon splitting + flavour creation • Different fragmentation characteristic: soft charm FF for gluon jets • Results promising; more statistic needed Andre Mischke (UU)

  18. Nuclear modification factor Andre Mischke (UU)

  19. Single electron RAA One of the most surprising results from RHIC STAR PHENIX light hadrons • Electron yield at high-pT stronger suppressed than expected • Models implying D and B energy loss are inconclusive yet • Large suppression requires extreme conditions; DGLV: dNg/dy = 3500 Andre Mischke (UU)

  20. Hope? – AdS/CFT • Heavy quarks lose momentum according to dp/dt = −p/Q + stochastic • Equilibration times Qare roughly consistent with single electron RAA Andre Mischke (UU)

  21. Open heavy-flavour in Pb+Pb in ALICE D0 Kp Open bottom reconstruction through displaced electrons D0 Kp S/B ≈ 10 % S/(S+B) ≈ 40 1 year @ nominal luminosity 107(109) central Pb+Pb(p+p) events B  e+X mb = 4.8 GeV Andre Mischke (UU)

  22. Heavy-flavour energy loss at LHC Colour charge dependence Mass hierarchy • More details on heavy-flavour quenching mechanism • RcAA/RbAA ratio different for pQCD and AdS/CFT Andre Mischke (UU)

  23. Single electron – D0 correlations Andre Mischke (UU)

  24. compilation by A.M. 2009 D and B contribution to single electrons • FONLL has large uncertainty around the Be / Decrossing point (RHIC: 3 < pT < 10 GeV/c) • Crossing point at LHC similar to that at RHIC • Separate De and Be contribution experimentally − c  e± + X (BR = 9.6%) -- b  e± + X (BR = 10.86%) M. Cacciari et al., PRL 95, 122001 (2005) Andre Mischke (UU)

  25. Single electron-tagged correlations trigger NLO pQCD: D/B meson crossing point is largely unknown Near side: study D/B decay contribution to single electrons? M. Cacciari et al., PRL 95, 122001 (2005) A. M., PLB 671, 361 (2009) PYTHIA, pp@200 GeV bottom dominant Away side: study in-medium D/B lose energy? conical emission? charm dominant Andre Mischke (UU)

  26. Electron-hadron correlations in STAR • B and D contributions comparable at pT > 5 GeV/c and consistent with FONLL • Similar result from PHENIX (PRL 103, 082002) • Bottom stronger suppressed than expected? Andre Mischke (UU)

  27. Single electron RAA at LHC Pyquen: Pb+Pb(5%)@5.5 TeV H. van Hees and R. Rapp, 2007 T0 = 1 GeV t0 = 0.15 fm/c # quark flavours: 2 I. Vitev, A. Adil & H. van Hees, 2007 • Pyquen • Pythia afterburner • Radiative (generalisation of BDMPS) and collisional energy loss (high-pT approximation) Andre Mischke (UU)

  28. Single electron – D0 angular correlations 2 < pTtrigger ele< 4 GeV/c Pythia Pyquen • Near side: B decays + gluon splitting charm • Away side: charm flavour creation 900M events Andre Mischke (UU)

  29. NLO processes charm GS charm + B decays GS charm only E. Norrbin and T. Sjostrand, Eur. Phys. J. C17, 137 (2000) bottom NLO processes (such as gluon splitting) become important at LHC Andre Mischke (UU)

  30. Df(e, D0): Near-side width and IAA 2 < pTtrigger ele< 4 GeV/c IAA of near-side yield • Broader peak for Pyquen than Pythia • Suppression of D0 yield for Pyquen • Next: fragmentation function Andre Mischke (UU)

  31. Summary • Heavy quarks are particularly good probes to study the properties of hot QCD matter (especially transport properties) • RHIC (200 GeV) • energy loss of heavy quarks in the medium larger than expected  energy loss mechanism not fully understood yet (bottom stronger suppressed as expected ?) • LHC (14 and 5.5 TeV) • - pp data are important baseline measurements • inclusive charm production cross section & spectral shape: test pQCD- relevant for suppression measurements of Quarkonia states • NLO processes (like gluon splitting) become important: accessible by “charm content in jets” measurements • Jet-like heavy-flavour particle correlations: modification of the fragmentation function • First heavy-ion collisions anticipate in fall 2010 • Exciting time ahead of us… Pythia  pp Pyquen  PbPb Andre Mischke (UU)

  32. Backup Andre Mischke (UU)

  33. Electron identification Data MC (p0+Ke3) p0 Dalitz and g conversion (MC) Ke3 decays (MC) • PHENIX • Electromagnetic calorimeter and RICH at mid rapidity • pT< 5 GeV/c • STAR • ToF + TPC • pT< 4 GeV/c • EMCal + TPC • pT > 1.5 GeV/c E/p Andre Mischke (UU)

  34. Photonic electron background -g e+ + e-(small for Phenix) - p0g + e+ + e- - h, w, f, etc. Phenix is almost material free  their background is highly reduced compared to STAR Background is subtracted by two independent techniques - very good consistency between them - converter method (1.68% X0) - cocktail method STAR determines photonic background using invariant mass Phenix e+ e- e- dca  mass (GeV/c2) Electron background sources STAR Andre Mischke (UU)

  35. Electron-hadron correlations in PHENIX p+p • Use e-K invariant mass • Statistics limited • Mid-rapidity electron and forward-rapidity muon -> promissing… arXiv:0903.4851 Andre Mischke (UU)

  36. Charmonium contribution to single electrons • New study takes J/ e±+X contribution into account • 1/3 of single electrons are from J/ decays for pT > 5 GeV/c  up to 16% decrease in open heavy • But what is RAA of high-pT J/ ? • Background contribution from K0s decays may also play a role (especially at low-pT)  under investigation 1/3 of e from J/ decays Andre Mischke (UU)

  37. Charm and bottom RAA pT > 5 GeV/c • Knowing RAA of single electrons and relative B contribution rB in p+p collisions, one can study RAA(b) as a function of RAA(c): • Exclude original radiative calculation • D and B measurements in A+A necessary RAA = rB RAA(b) + (1-rB) RAA(c) I: Djordjevic, Gyulassy, Vogt and Wicks, PLB 632 (2006) 81; dNg/dy = 1000 II: Adil and Vitev, PLB 649 (2007) 139 III: Hees, Mannarelli, Greco and Rapp, PRL 100 (2008) 192301 Andre Mischke (UU)

  38. Single electron-hadron correlations in Au+Au STAR preliminary • Away-side modification? • Improved statistics and better background rejection needed • Similar analysis in PHENIX Andre Mischke (UU)

  39. D* in jets UA1 jet reconstruction - cone size 0.4 - Ethr = 10 GeV/c2 Andre Mischke (UU)

  40. Heavy-flavour production at LHC system, sNN pp @ 14 TeV Pb+Pb (0-5%) @ 5.5 TeV 11.2 / 0.5 4.3 / 0.2 0.16 / 0.006 115 / 4.6 • Heavy flavour copiously produced • Charm and bottom yields (NLO pQCD predictions using MNR PDF) Andre Mischke (UU)

  41. Kinematics for c-cbar pairs ALICE (central barrel) acceptance Δϕ Δη Gluon splitting Andre Mischke (UU)

  42. Df(e,D0) correlations for like-sign pairs Andre Mischke (UU)

  43. Near-side width and yield Andre Mischke (UU)

  44. Near-side IAA Andre Mischke (UU)

  45. Relevant heavy-flavour decay modes • Charm • charmed meson modes c  D0 + X (BR = 56.5%)c  D+ + X (BR = 23.2%)c  D*+ + X (BR = 23.5%) • semileptonic channelc  e+ + X (BR = 9.6%)  single (non-photonic) electron continuum • Bottom • charmed meson modes b  D0 + X (BR = 59.6%) b  D- + X (BR = 23.5%)b  D*+ + X (BR = 17.3%) • semileptonic channelb  e+ + X (BR = 10.86%) Based on e+e- data from CLEO/ARGUS and LEP experiments Review of Particle Physics, C. Amstler et al. (Particle Data Group), Physics Letters B667, 1 (2008). Andre Mischke (UU)

  46. LHC running conditions pp nominal run Pb-Pb nominal run Ldt dt = 3.1030 cm-2 s-1 x 107 s 5.1037 cm-2 for pp run, 14 TeV Npp collisions = 2 .1012 collisions Ldt = 5.1026 cm-2 s-1 x 106 s 5.1032 cm-2 PbPb run, 5.5 TeV NPbPb collisions = 2 .109 collisions   Muon triggers: ~ 100% efficiency, < 1kHz Muon triggers: ~ 100% efficiency, ~ 1kHz Electron triggers: ~ 50% efficiency of TRD L1 20 physics events per event Electron triggers: Bandwidth limitation NPbPb central = 2 .108 collisions Hadron triggers: Npp minb = 2 .109 collisions Hadron triggers: NPbPb central = 2 .107 collisions   Andre Mischke (UU) 46

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