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Heavy Flavor measurements with the ALICE EMCAL detector

Heavy Flavor measurements with the ALICE EMCAL detector. Mark Heinz Yale University EMCAL Meeting, Nantes, July 16, 2008. Outline . Heavy flavor physics with EMCAL The Essentials Simulation Status at CD-2 What needs to be done for PPR 2008. B-tagging algorithms

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Heavy Flavor measurements with the ALICE EMCAL detector

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  1. Heavy Flavor measurements with the ALICE EMCAL detector Mark Heinz Yale University EMCAL Meeting, Nantes, July 16, 2008

  2. Outline • Heavy flavor physics with EMCAL • The Essentials • Simulation Status at CD-2 • What needs to be done for PPR 2008. • B-tagging algorithms • The Optionals (“exciting future measurements”) • Outlook & Summary EMCAL Meeting Nantes, July 2008

  3. Testing pQCD • Current theoretical estimates for bottom and charm production at LHC still have large uncertainties. • Charm x-section measurements disagree at RHIC for STAR and PHENIX by a significant amount. Large uncertainty in cross-sections Theory Uncertainties: NLO pQCD, pp, s = 14 TeV CERN/LHCC 2005-014, hep-ph/0601164 EMCAL Meeting Nantes, July 2008

  4. Medium effects on Heavy quarks • Parton energy loss in the medium • Magnitude of Dead-cone effect and quark mass dependence within a limited kinematical range • Quark vs gluon energy loss in the medium (Color Factors) • B-jets constitute a very pure sample of quark jets. • Distinction between AdS/CFT and pQCD? WHDG, nucl-th/0512076 EMCAL Meeting Nantes, July 2008

  5. The Essentials

  6. Annual Heavy Flavor electrons vs backgrounds • More detailed rate-plot for 1 year of Pb+Pb running in EMCAL acceptance. EMCAL Meeting Nantes, July 2008

  7. Electron/Hadron ratio • We will need to identify high-pt (>10 GeV/c) electrons. How large are the hadron backgrounds? • Track-EMCAL cluster matching • Max. track-matching efficiency for electrons in Hijing events with tuned EMCAL cuts is ~90% up to 30 GeV/c ~400 EMCAL Meeting Nantes, July 2008

  8. EMCAL PID (electron vs hadron) • Using matched cluster track-pairs we determine the momentum/Energy (p/E) ratio of tracks Resolution of p/E peak for two different energies Electrons Pions EMCAL Meeting Nantes, July 2008

  9. Background Electron Sources • Full Simulation of photons in ALIROOT v4-06 include newer GEANT model of TOF-Geometry (additional material) PYTHIA+GEANT Simulation of mono-energetic photons Integrated over area of EMCAL Start of EMCAL: 454cm <10% convert before TRD/TOF EMCAL Meeting Nantes, July 2008

  10. Statistical reach of B-jets • By triggering on high-pt electrons tightly correlated with the b-jet (Cone dR<0.2) we are biasing our sample to high pt B-jets. • For 70 GeV/c B-jets we obtain about a factor 5 more statistics using a electron trigger • A sample of several hundred B-jets with momenta up to 80 Gev/c will be acquired during 1 month Pb-Pb running EMCAL Meeting Nantes, July 2008

  11. /e K Pe+K e- CDF Phys.Rev.D66 (2002)) D0 SecVtx r B- PrimVtx Lxy B-tag: A method - Displaced Vertex Method • The method pursued here has previously been used by CDF to identify secondary vertices from semi-leptonic decays. • Breakdown of method: • Find a high-pt electron trigger particle in EMCAL • Pair with all charged hadrons within a cone of radius dR. • Reconstruct “approximate” (average between B-D decay) secondary vertex and apply more cuts to reduce backgrounds from other leptonic decays. • Plot Lxy distribution and obtain B-contribution from positive/negative imbalance Lxy= r .pe+k / |pe+k| EMCAL Meeting Nantes, July 2008

  12. Charm backgrounds (dominant source) • Due to the shorter life-time secondary vertices will naturally have a narrower Lxy distribution. • To further reduce displaced vertices from charm by cutting on the electron-hadron M_inv. • Me+h < Mn + Me + Mh = MD ~ 1.9 GeV Charm (after cut) Beauty (after cut) EMCAL Meeting Nantes, July 2008

  13. Signal vs. Backgrounds Cuts used for analysis • Electron pT-cut > 10 GeV/c • Min. 6 ITS-hits on both electron/hadron track • Inv mass of (elec-kaon) mass > 1.7 GeV • Pair DCA < 200 m • B-Tag = |Lxy| > 600 m Backgrounds EMCAL Meeting Nantes, July 2008

  14. Efficiencies & Rejection More stats needed, higher pT B-jets B-jets All sources Dalitz B-jets B-jets Charm Conversions EMCAL Meeting Nantes, July 2008

  15. W backgrounds So far only a qualitative look ~10x higher stats B-jet electrons W electrons pT pT EMCAL Acceptance EMCAL Acceptance h h EMCAL Meeting Nantes, July 2008

  16. DVM Comparison: B-jet vs W B-jets W Blue = Signal = right - left Standard cuts Standard cuts + Minv> 1.7 GeV (charm rejection) Standard cuts + Minv> 1.7 GeV + Max ITS-hits EMCAL Meeting Nantes, July 2008

  17. Electrons from all sources (before DVM method) Electrons from all sources (after DVM method) Displaced Vertex simulation results After applying DVM cuts the signal efficiency is ~30-40%, whereas the backgrounds are factor ~100 suppressed. EMCAL Meeting Nantes, July 2008

  18. What needs to be done ?(short-term until PPR)

  19. PPR 2008 • Physics Performance Report (PPR) will be prepared for EMCAL for end of 2008. • Effort lead by Rene Bellwied • 6 different topical working groups formed • All current studies need to be upgraded with more statistics and current version of AliRoot • Electron-Hadron-ID needs to be checked with results from 2007 Testbeam to ensure stability EMCAL Meeting Nantes, July 2008

  20. Preliminary work matrix (PPR) EMCAL Meeting Nantes, July 2008

  21. non phot. el. Non-photonic Electron R-AA • Most importantly compare to measurements in Alice with TPC and TPC+TRD to identify a kinematic regime where EMCAL is unique. • How will the EMCAL triggering help enhance our yields ? • Determine photonic conversion probabilities and develop conversion vertex rejection methods ? EMCAL Meeting Nantes, July 2008

  22. B-tagging • Start of with jet-finding algorithm • A brief overview of some different algorithms for b-tagging (see studies by CDF,D0,CMS…) • Secondary, displaced vertex type algorithm (Karlsruhe) • Soft lepton tag (INFN) • Track-impact parameter based (INFN PISA) • In the end several tags can always be combined in a linear discriminant (LDA) method. EMCAL Meeting Nantes, July 2008

  23. CMS Secondary Vertex Tracker (Weiser et al.) CMS Note 2006/14 EMCAL Meeting Nantes, July 2008

  24. B-Tagging: Track Impact Parameter Based Tagging Variables • More details in CMS-Note (Rizzi et al, INFN Pisa) 2006/19 First studies were started in Alice by Bonvini, Antinori et al (PWG3, Sep 2007) EMCAL Meeting Nantes, July 2008

  25. “Exciting new measurements” My personal selection of QM 08 high-lights High-Pt J/Y Electron-Charm correlations

  26. Electron-Charm correlations EMCAL Meeting Nantes, July 2008

  27. w/ non-photonic electron trigger Clear D0 signal w/o background subtraction (K) invariant mass distribution w/o electron trigger EMCAL Meeting Nantes, July 2008

  28. Electron – Charm correlations (2) A. Mischke (HP 2008) EMCAL Meeting Nantes, July 2008

  29. J/ at high-pT • Investigate heavy quarkonium production mechanism and hadronization • In p+p collision • Gluon fusion • Charm fragmentation • Feed down • In heavy ion collision • Gluon energy loss • Heavy quark energy loss • Hot-wind dissociation in QGP Zebo Tang (STAR) QM08 EMCAL Meeting Nantes, July 2008

  30. High-pT J/ Dissociation or not? • Double the pT range to 10GeV/c • Consistent with no suppression at high pT: RAA(pT>5 GeV/c) = 0.9±0.2 • Low pT: RAA(pT<4 GeV/c) = ~0.5 • Indicates RAA increase from low pT to high pT • Most models expect a decrease RAA at high pT: AdS/CFT: • H. Liu, K. Rajagopal and U.A. Wiedemann, • PRL 98, 182301(2007) and hep-ph/0607062 • Two Component Approach: • X. Zhao and R. Rapp, hep-ph/07122407 • private communication Zebo Tang (STAR), QM08 EMCAL Meeting Nantes, July 2008

  31. J/Psi – hadron correlations EMCAL Meeting Nantes, July 2008

  32. J/Psi – hadron correlations Zebo Tang (STAR), QM08 EMCAL Meeting Nantes, July 2008

  33. Summary • Baseline studies were performed for US CD-2 document in Dec 2007 • Need to be updated and improved • EMCAL Physics Performance Report (PPR) is next deadline • Structure & meetings are in place • We need to continue to watch new results from RHIC • More studies of other observables need to be started now with a goal of having simulations beyond the PPR EMCAL Meeting Nantes, July 2008

  34. Backup EMCAL Meeting Nantes, July 2008

  35. Z-Boson decay into electrons Dielectron decays: • Main source of background are jets from misidentified pions. • An isolation cut is mandatory. A track i is rejected if it is found a track j with • pt > 2 GeV/c • ||  0.1 && ||  0.1 rad Zaida . , HP2008 R. Bailhache et al: Proc. QM08, EMCAL Meeting Nantes, July 2008

  36. D0 measurement of weak boson PRL 1995 EMCAL Meeting Nantes, July 2008

  37. Z/W predictions from Tevatron toLHC • Probe PDF’s EMCAL Meeting Nantes, July 2008

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