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Charm and beauty with ALICE at LHC

Charm and beauty with ALICE at LHC. Rosario Turrisi University and INFN, Padova, Italy for the ALICE Collaboration. Contents. Why heavy ions at LHC The ALICE detector The role of charm and beauty Basic performances Open flavors measurement sensitivity Conclusions and Perspectives. LHC

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Charm and beauty with ALICE at LHC

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  1. Charm and beauty with ALICE at LHC Rosario Turrisi University and INFN, Padova, Italy for the ALICE Collaboration

  2. Contents Rosario Turrisi Beach 2004 Saturday, July 03, 2004 • Why heavy ions at LHC • The ALICE detector • The role of charm and beauty • Basic performances • Open flavors measurement sensitivity • Conclusions and Perspectives

  3. LHC PbPb @ = 5.5 TeV Why heavy ions at LHC Rosario Turrisi Beach 2004 Saturday, July 03, 2004 high energy & large volume hadronic matter strong interaction plasma of quarks and gluons QGP • At SPS (CERN) and RHIC (BNL) already • observed deconfinement signals. • At LHC: • morestrictlyμB=0 • higher energy density • DEEP DECONFINEMENT! Tc~ 170 MeV (μB=0) c ~ 1 GeV/fm3 Lattice QCD with massless flavors Baryon free environment (μB=0) Exploration of the deconfined phase…

  4. rf: 50 mm 9.8 Mch z: 425 mm PIXEL CELL Two layers: r = 4 – 7 cm Solenoid magnet B<0.5 T TPC (the largest ever…): 88 m3 , 510 cm length, 250 cm radius Ar (90%) + CO2 (10%) 88 μs drift time main tracking device, dE/dx Rosario Turrisi Beach 2004 Saturday, July 03, 2004 ALICE detectors • 6 Layers, 3 technologies • Material budget < 1% of X0 per layer! • Silicon Pixels vertices resolution in xy • (0.2 m2, 9.8 Mchannels) • Silicon Drift  resolution in z • (1.3 m2, 133 kchannels) • Double-sided Strip  connection w/TPC • (4.9 m2, 2.6 Mchannels) • Central tracking system: • Inner Tracking System • Time Projection Chamber 2 * 1.8 units of pseudo-rapidity

  5. 2 * 1.8 units of pseudo-rapidity Rosario Turrisi Beach 2004 Saturday, July 03, 2004 ALICE detectors • 6 layers for: • electron/pion separation at pt>1 GeV • factor 100 rejection at 2 GeV • tracking complement, mass resolution • 100 MeV/c2 @  • high pt trigger (onia studies) • Central tracking system: • Transition Radiation Detector • Time Of Flight Multigap Resistive Plate Chambers 5 years R&D, and  < 100 ps pions, kaons, protons separation (see later) electrons/pions at low pt

  6. Cosmic rays trigger • Forward detectors: • Photon Mult. Det. • Forward Mult. D., T0, V0, Zero Degrees Cal. Rosario Turrisi Beach 2004 Saturday, July 03, 2004 ALICE detectors • Specialized detectors: • High Momentum PID • PHOton Spectrometer { MUON Spectrometer 2.4 <  < 4 +EMCal (under discussion)

  7. not covered here PbPb @ =5.5 TeV Heavy flavors and heavy-ions Rosario Turrisi Beach 2004 Saturday, July 03, 2004 Why measure heavy flavors at LHC ? • quarkonium suppression: deconfinement signature • B J/ important background • open heavy flavors as natural normalization for QQ studies • interest in its own right (discovery potential!) • probes of the medium: • early formation (initial parton-parton), most energetic phase • energy loss (medium dependent?) pp reactions, pQCD, nuclear effects (geometry, shadowing) INPUT OUTPUT medium properties

  8. Rosario Turrisi Beach 2004 Saturday, July 03, 2004 pQCD predictions • NLO pQCD (Mangano-Nason-Ridolfi), average of MRST e CTEQ5M PDF’s, EKS98 in Pb-Pb for shadowing (shadowing = modification of PDF’s, causes reduction of cross section) Taking into account F,R a factor 4 arises between min. and max. cross section… in central collisions Mesons multiplicities In acceptance: ~5 D0  K ~0.85 B  eX

  9. Performance studies Rosario Turrisi Beach 2004 Saturday, July 03, 2004 • Detector description with the state-of-the-(ALICE)-art code AliRoot • Charm/beauty signal tuned to NLO pQCD pt spectrum (custom tuning of PYTHIA) • Background from HIJING, 6000 charged particles per unit rapidity at midrapidity Priorities: • the exclusive decay of the D0  K (golden channel): • test bench for secondary vertex detection, pid • very high background • inclusive b  eX decay • secondary vertices • electron identification • “easy” measurement of cross section

  10. TPC + ITS projection of the full  range (front view) Total charged multiplicity Rosario Turrisi Beach 2004 Saturday, July 03, 2004 dNCH/dy (y=0) Current baseline: 6000 Tested up to: 8000 60 <  < 62

  11. pt resolution: σ= 1(2)% @ 1(10) GeV 9% @ 100 GeV EFFICIENCY pions kaons Tracking performance Rosario Turrisi Beach 2004 Saturday, July 03, 2004 impact parameter resolution:  σ= @ pt=1.3 GeV < 50 μm   < 150 μm z

  12. test beam: p id. as e = 1 % PID: e,, K, p Rosario Turrisi Beach 2004 Saturday, July 03, 2004 PbPb events dN/dy=6000 Combined π/e ~ 10-4 @ pt~1-2 GeV electrons TPC p (Gev/c) TRD TOF hadrons

  13. Selection cuts Rosario Turrisi Beach 2004 Saturday, July 03, 2004 • D0  K • decay topology • impact parameter of tracks (in bending plane, d0~100 μm) • momenta • identification ~ 0.5 D0 with |y|<1 but also 12000 charged /K in PbPb collisions impact parameters product

  14. Significance Performance: D0K Rosario Turrisi Beach 2004 Saturday, July 03, 2004 • K, MINV integrated over pt • 107 PbPb events (one-month run) • dN/dy(y=0) = 6000 (charged) measurement of pt distribution

  15. g c path length L h RAA measured at RHIC with pions: clear quenching effect Quark energy loss: basics Rosario Turrisi Beach 2004 Saturday, July 03, 2004 • Origin: parton energy loss due to gluon radiation • Average energy loss (BDMPS model): CR Casimir factor = 3 for gluons 4/3 for quarks q = medium transport coefficient  gluon density and momenta • Study to get the medium effect RAA =1 means AA is superposition of independent pp collisions Quark Matter Conference ’04 R.Baier, Yu.L.Dokshitzer, A.H.Mueller, S.Peigne' and D.Schiff, Nucl. Phys. B483 (1997) 291. C.A.Salgado and U.A.Wiedemann, Phys. Rev. D68 (2003) 014008 [arXiv:hep-ph/0302184].

  16. Energy loss with charm? Rosario Turrisi Beach 2004 Saturday, July 03, 2004 • Effect present in light mesons, what about other particles? • D meson originate from c quark Cr = 4/3, whereas light flavors originate mainly from gluons (C=3) • Dead cone effect*: due to destructive interference, gluons radiation is suppressed at angles  < mQ/EQ *Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett. B519 (2001) 199 [arXiv:hep-ph/0106202]. bars= statistical error shadow= syst. err. (MC+centrality+theory extr.) q = 4 GeV2/fm at LHC requiring same hadron suppression as at RHIC nuclear shadowing effect (shadowing = modification of PDF’s, causes reduction of cross section)

  17. q = 4 GeV2/fm at LHC requiring same hadron suppression as at RHIC Energy loss vs. dead cone Rosario Turrisi Beach 2004 Saturday, July 03, 2004 Quantitative difference heavy/light mesons measurement? E gluons/quarks energy loss ~ 2 Egluons/quarks fragmentation ~ 1/2 D/h ratio: RD/h = RAAD / RAAh dead cone makes the difference! RD/h ~ 2 in hot QGP sensitive to medium density

  18. b e+X: strategy Rosario Turrisi Beach 2004 Saturday, July 03, 2004 • Task: tag ~ 0.8 e /event from b decays among ~ 103 electrons from other sources • Main backgrounds: • pions misidentified as electrons • Dalitz decays • charm semi-electronic decays • photon conversions in the detector materials • strange decays • Strategy: • high impact parameter: c ~ 500 μm for beauty • high momenta: beauty harder than lighter flavors • electron/pion separation critical

  19. Pt and d0 comparison Rosario Turrisi Beach 2004 Saturday, July 03, 2004 beauty electrons charm electrons charged pions

  20. background cure charm electrons pt thr. light mesons electrons d0 thr. charged pions identification pT> 3 GeV pT> 2 GeV pT> 1 GeV b e+X: purity and statistics Rosario Turrisi Beach 2004 Saturday, July 03, 2004 pT>2 GeV, 180  d0 400mm • 90% purity • 50,000 B's (including TRD efficiency)

  21. pT> 3 GeV pT> 2 GeV pT> 1 GeV Conclusions & perspectives Rosario Turrisi Beach 2004 Saturday, July 03, 2004 • ALICE has a good potential to measure heavy flavors in different channels • Charm: • production cross section • pt distribution • study of charm energy loss • Beauty: • Production cross section • Coming up • b’s pt distribution • additional D, D* channels • semi-electronic b/c deconvolution • exclusive b decays 11% S/B, significance=37

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