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Some Aspects of Heavy Flavor Physics in ALICE: the “Other” Hard Probe

Some Aspects of Heavy Flavor Physics in ALICE: the “Other” Hard Probe. V. Ghazikhanian UCLA.  l. Heavy Quark Production Mechanism. K +. e - /  -. e - /  -. e + /  +. J/ y. K -. e + /  +.  l. D 0. Sensitive to initial gluon density and gluon distribution.

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Some Aspects of Heavy Flavor Physics in ALICE: the “Other” Hard Probe

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  1. Some Aspects of Heavy Flavor Physics in ALICE: the “Other” Hard Probe V. Ghazikhanian UCLA ALICE-USA Collaboration Meeting, LBNL

  2. l Heavy Quark Production Mechanism K+ e-/- e-/- e+/+ J/y K- e+/+ l D0 • Sensitive to initial gluon density and gluon distribution • Sensitive to initial gluon density and gluon distribution • Energy loss when propagating through dense medium • Suppression/enhancement of charmonium in the medium is a critical signal for QGP. • Different scaling properties in central and forward region indicate shadowing, which can be due to CGC. to these one needs to add photoproduction mechanism (see Spencer’s presentation) ALICE-USA Collaboration Meeting, LBNL

  3. Parton Distribution Function A. Dainese, PhD. Thesis [arXive:nucl-ex/0311004 ALICE-USA Collaboration Meeting, LBNL

  4. path length L hard parton Parton Energy Loss • Due to medium-induced gluon radiation • Average energy loss (BDMPS model): Casimir coupling factor: 4/3 for quarks 3 for gluons Medium transport coefficient gluon density and momenta R.Baier, Yu.L.Dokshitzer, A.H.Mueller, S.Peigne' and D.Schiff, (BDMPS), Nucl. Phys. B483 (1997) 291. ALICE-USA Collaboration Meeting, LBNL

  5. ALICE Heavy Flavor Acceptance arXive:hep-ph/0311048 v1 4 Nov. 2003 ALICE-USA Collaboration Meeting, LBNL

  6. Some Heavy flavor quenching observables • Inclusive: • Suppression of dilepton invariant mass spectrum • Suppression of lepton spectra • Non-photonic electrons • Exclusive jet tagging: • High- pT lepton ( )&displaced vertex • Hadronic decay (ex. D0K-p+) &displaced vertex ALICE-USA Collaboration Meeting, LBNL

  7. Open Charm Production At LHC/ALICE A. Dainese, PhD. Thesis [arXive:nucl-ex/0311004 ALICE-USA Collaboration Meeting, LBNL

  8. Detecting D-Mesons via Hadronic Decays • Hadronic Channels: • D0  K(B.R.: 3.8%) • D0  K p r(B.R.: 6.2%  100% (rp+p-) = 6.2%) • D K p(B.R.: 9.1%) • D*±D0π (B.R.: 68%  3.8% (D0  K) = 2.6%) • Lc p K p (B.R.: 5%) Huan Huang ALICE-USA Collaboration Meeting, LBNL

  9. Detection strategy for D0 K- p+ • Weak decay with mean proper length ct = 124 μm • Impact Parameter (distance of closest approach of a track to the primary vertex) of the decay products d0 ~ 100 μm • STRATEGY: invariant mass analysis of fully-reconstructed topologies originating from (displaced) secondary vertices • Measurement of Impact Parameters • Measurement of Momenta • Particle identification to tag the two decay products A. Dainese, PhD. Thesis [arXive:nucl-ex/0311004 ALICE-USA Collaboration Meeting, LBNL

  10. Hadroniccharm Combine ALICE tracking + secondary vertex finding capabilities (sd0~60mm@1GeV/c pT) + large acceptance PID to detect processes asD0K-+ ~1 in acceptance / central event ~0.001/central event accepted after rec. and all cuts Results for 107 PbPb ev. (~ 1/2 a run) significance vs pT S/B+S ~ 37 S/B+S ~ 8 for 1<pT<2 GeV/c (~12 if K ID required) ALICE-USA Collaboration Meeting, LBNL

  11. Initial Signal Significance A. Dainese, PhD. Thesis [arXive:nucl-ex/0311004 ALICE-USA Collaboration Meeting, LBNL

  12. mc PDFs scales pp, 14 TeV down to 1 GeV/c! down ~ 0! D0 Cross section measurement ALICE-USA Collaboration Meeting, LBNL

  13. A.Dainese nucl-ex/0311004 q …medium transport coefficient depends on gluon density, momenta D quenching (D0K-p+ ) Ratio D/hadrons (or D/π0) enhanced and sensitive to medium properties ALICE-USA Collaboration Meeting, LBNL

  14. V2 of J/psi V2 of J/psi can differentiate scenarios ! pQCD direct J/psi should have no v2 ! Recombination J/psi can lead to non-zero v2 ! ALICE-USA Collaboration Meeting, LBNL

  15. Detecting Charm/Beauty via Semileptonic D/B Decays • Semileptonic Channels: • D0  e+ + anything(B.R.: 6.87%) • D e + anything(B.R.: 17.2%) • B e + anything(B.R.: 10.2%)  single “non-photonic” electron continuum • “Photonic” Single Electron Background: • g conversions (p0 gg) • p0, h Dalitz decays • r, f, … decays (small) • Ke3 decays (small) ALICE-USA Collaboration Meeting, LBNL

  16. J/ Y 103 Events/100 MeV 102 dN/dh=8000 5 10 15 0 c/b Quarkonia • 1 month statistics of PbPb √sNN=5.5 TeV arXive:hep-ph/0311048 v1 4 Nov. 2003 ALICE-USA Collaboration Meeting, LBNL

  17. Heavy Flavor Production Yields (I) Peter J. ALICE-USA Collaboration Meeting, LBNL

  18. Hadron and Lepton Identification ALICE PPR CERN/LHCC 2003-049 ALICE-USA Collaboration Meeting, LBNL

  19. Summary/Outlook • ALICE Heavy flavor Physics is complementary to that of RHIC and will extend x reach where Gluon structure function dominates. • just as in RHIC (and perhaps even more) one needs to follow a program of complete set of measurements (RAA, RCP, dN/dY, v2, …) for AA systems, and also need yields from pp and pA for open charm (beauty) and quarkonium states. [pp and pA will provide information on basic production rates and nuclear shadowing effects (and nuclear absorption/energy loss), respectively]. • Need to have good control over photonic vs. non-photonic electrons in semileptonic open charm/beauty decay (TRD needed in front of EMC, TOF and EMC to extend pT ~ 3-10 GeV/c in order to extend PID in the region where b contribution dominates that of c quarks)! • Trigerring on heavy flavor mesons: high pt electrons (high tower trigger in EMC, TRD), also triggering on muons in the muon spectrometer + electrons in EMC (to look for b decay chain proceeding via b -> mu + c -> e (EMC)). • more studies are needed both on theory front and experimental side [e.g., better energy loss estimates for partons in deconfined nuclear matter/QGP and for quarkonia; need further simulation on detector/trigger performance for TRD+EMC+TOF+ITS]. ALICE-USA Collaboration Meeting, LBNL

  20. The End ALICE-USA Collaboration Meeting, LBNL

  21. Nuclear Modification Factors Use number of binary nucleon-nucleon collisions to scale the colliding parton flux: N-binary Scaling  RAA or RCP = 1 simple superposition of independent nucleon-nucleon collisions ! ALICE-USA Collaboration Meeting, LBNL

  22. Y. Dokshitzer et al, J Phys G 17, 1602 (1991) Heavy Quarks and Quarkonia • For Heavy Quarks with momenta < 20–30 GeV/cv << c • Gluon radiation is suppressed at angles • “dead-cone” effect • Contributes to the harder fragmentation of heavy quarks and implies lower energy loss for heavy quarks relative to light quarks D mesons quenching reduced Ratio D/hadrons (or D/p0) enhanced and sensitive to medium properties Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett. B519 (2001) 199 [arXiv:hep-ph/0106202]. ALICE-USA Collaboration Meeting, LBNL

  23. Heavy Flavor Production Yields (II) arXive:hep-ph/0311048 v1 4 Nov. 2003 ALICE-USA Collaboration Meeting, LBNL

  24. Heavy Flavor Production Yields (III) arXive:hep-ph/0311048 v1 4 Nov. 2003 ALICE-USA Collaboration Meeting, LBNL

  25. Charm pT Spectra D0 and e combined fit Power-law function with parameters dN/dy, <pT> and n to describe the D0 spectrum Generate D0e decay kinematics according to the above parameters Vary (dN/dy, <pT>, n) to get the min. 2 by comparing power-law to D0 data and the decayed e shape to e data <pT>=1.20  0.05(stat.) GeV/c in minbias Au+Au <pT>=1.32  0.08(stat.) GeV/c in d+Au ALICE-USA Collaboration Meeting, LBNL

  26. Charm Total Cross Section Charm total cross section per NN interaction 1.13  0.09(stat.)  0.42(sys.) mb in 200GeV minbias Au+Au collsions 1.4  0.2(stat.)  0.4(sys.) mb in 200GeV minbias d+Au collisions Charm total cross section follows roughly Nbin scaling from d+Au to Au+Au considering errors Indication of charm production in initial collisions Systematic error too large ! ALICE-USA Collaboration Meeting, LBNL

  27. Charm and Non-photonic Electron Spectra 1.13  0.09(stat.)  0.42(sys.) mb in 200GeV minbias Au+Au collsions Total charm  Binary Scaling suppression at high pT ALICE-USA Collaboration Meeting, LBNL

  28. Charm Nuclear Modification Factor RAA suppression for single electron in central Au+Au similar to charged hadrons at 1.5<pT<3.5 GeV/c Heavy flavor production IS also modified by the hot and dense medium in central Au+Au collisions at RHIC Suppressions!! STAR: Phys. Rev. Lett. 91 (2003) 172302 ALICE-USA Collaboration Meeting, LBNL

  29. electrons hadrons d K p p electrons High pT Electron ID dE/dx from TPC SMD from EMC ALICE-USA Collaboration Meeting, LBNL

  30. electrons hadrons High pT Electron ID p/E from EMC After all the cuts ALICE-USA Collaboration Meeting, LBNL

  31. STAR non-photonic electrons from EMC ALICE-USA Collaboration Meeting, LBNL

  32. Does Charm Quark Flow Too ? Reduce Experimental Uncertainties !! Suppression in RAA Non-zero azimuthal anisotropy v2 ! ALICE-USA Collaboration Meeting, LBNL

  33. HG Color Screening • J/ • Small: r ~ 0.2 fm • Tightly bound: Eb ~ 640 MeV QGP • Observed in dileptons invariant mass spectrum • Other charmonia • ’~ 8% •  ~ 32% ALICE-USA Collaboration Meeting, LBNL

  34. QCD Color Screening:(T. Matsui and H. Satz, Phys. Lett. B178, 416 (1986)) A color charge in a color medium is screened similar to Debye screening in QED  the melting of J/y. Charm quarks c-c may not bind Into J/y in high T QCD medium c c The J/y yield may be increased due to charm quark coalescence at the final stage of hadronization (e.g., R.L. Thews, hep-ph/0302050) J/psi Suppression and Color Screening Recent LQCD Calculation: ALICE-USA Collaboration Meeting, LBNL

  35. J/y Quark Potential Model ALICE-USA Collaboration Meeting, LBNL

  36. Lattice QCD Calculations ALICE-USA Collaboration Meeting, LBNL

  37. J/psi is suppressed in central Au+Au Collisions ! Factor ~ 3 the same as that at SPS Satz: Only c states are screened both at RHIC and SPS. Alternative: Larger suppression in J/psi at RHIC due to higher gluon density, but recombination boosts the yield up ! ALICE-USA Collaboration Meeting, LBNL

  38. J/y Suppression or Not Nuclear Absorption of J/y important at low energy important (SPS) ! Both QCD color screening and charm quark coalescence are interesting, which one is more important at RHIC? At RHIC the J/y measurement requires high luminosity running! Centrality and pT dependence important ! ALICE-USA Collaboration Meeting, LBNL

  39. Collisions at high pT (pQCD) At sufficiently large transverse momentum, let us consider the process: p + p hadron + x • 1) f(x,m2) – parton structure function • 2) sab->cd – pQCD calculable at large m2 • 3) D(zh,m2) – Fragmentation function To produce heavy quark pairs, the CM energy must>2m ALICE-USA Collaboration Meeting, LBNL

  40. TOF electron measurements 2/ndf = 65/46 2/ndf = 67/70 Electrons can be separated from pions. But the dEdx resolution is worse than d+Au Log10(dEdx/dEdxBichsel) distribution is Gaussian. 0.3<pT<4.0 GeV/c |1/-1|<0.03 2 Gauss can not describe the shoulder shape well. • Exponential + Gaussian fit is used at lower pT region. • 3 Gaussian fit is used at higher pT region. ALICE-USA Collaboration Meeting, LBNL

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