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Harald Appelshäuser Goethe-Universität Frankfurt for the ALICE Collaboration

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  1. Particle Production at Large Transverse Momentum with ALICE Harald Appelshäuser Goethe-Universität Frankfurt for the ALICE Collaboration Harald Appelshäuser, Quark Matter 2011, Annecy, France

  2. Introduction J. D. Bjorken, FERMILAB-PUB-82-059-THY (1982) X.N. Wang and M. Gyulassy, PRL 68 (1992). Harald Appelshäuser, Quark Matter 2011, Annecy, France

  3. Introduction STAR, Quark Matter 2001 PHENIX, Quark Matter 2001 Harald Appelshäuser, Quark Matter 2011, Annecy, France

  4. RAA at RHIC - data • very detailed experimental • information available by now: • pT reach 20 GeV/c • identified hadrons, • leptons, photons • reaction plane dependence • pp and d-Au reference data Harald Appelshäuser, Quark Matter 2011, Annecy, France

  5. RAA at RHIC - models Bass et al, PRC79, 024901 • good description by theory • but extraction of medium • parameters still ambiguous Harald Appelshäuser, Quark Matter 2011, Annecy, France


  6. The Large Hadron Collider • pp up to √s=14 TeV • Pb-Pb up to • √sNN=5.5 TeV •  abundant production of hard probes 8,6 km Harald Appelshäuser, Quark Matter 2011, Annecy, France

  7. The Large Hadron Collider ALICE Collaboration, Phys. Lett. B696 (2011) day-1 physics! Harald Appelshäuser, Quark Matter 2011, Annecy, France

  8. ALICE Central Detectors: Inner Tracking System Time Projection Chamber Time-of-Flight Transition Radiation Detector Spectrometers: High Momentum PID (RICH) Photon Multiplicity Forward Multiplicity Muon Spectrometer Calorimeters: EM Calorimeter Photon Spectrometer (PHOS) Zero Degree Calorimeter Trigger: Trigger Detectors pp High-Level-Trigger Harald Appelshäuser, Quark Matter 2011, Annecy, France

  9. momentum resolution • combined TPC-ITS • momentum resolution: • σ(pT)/pT = 20% at pT = 100 GeV/c Harald Appelshäuser, Quark Matter 2011, Annecy, France

  10. Pb-Pb: charged particle spectra Talk: J. Otwinowski • charged particle spectra in • Pb-Pb at √sNN = 2.76 TeV • out to pT = 100 GeV/c • strong modification of the spectral • shape in central collisions Harald Appelshäuser, Quark Matter 2011, Annecy, France

  11. Pb-Pb: charged particle spectra Talk: J. Otwinowski • charged particle spectra in • Pb-Pb at √sNN = 2.76 TeV • out to pT = 100 GeV/c • strong modification of the spectral • shape in central collisions Harald Appelshäuser, Quark Matter 2011, Annecy, France

  12. pp: charged particle spectra Poster: M. Knichel • charged particle spectra • in pp at √s = 0.9, 2.76, 7 TeV • 2.76 TeV: reference measurement • for pp baseline Harald Appelshäuser, Quark Matter 2011, Annecy, France

  13. pp reference • pp reference spectrum derived from: • measured data points for pT≤ 5 GeV/c • extrapolation of Hagedorn fit for pT > 5 GeV/c CMS: 1104.3547 Harald Appelshäuser, Quark Matter 2011, Annecy, France

  14. RAA with new pp reference • good agreement with • published results • significant improvement of • systematic uncertainties Harald Appelshäuser, Quark Matter 2011, Annecy, France

  15. charged particle RAA • pronounced centrality • dependence below • pT = 50 GeV/c • minimum at • pT ≈ 6-7 GeV/c • strong rise in • 6 < pT < 50 GeV/c • no significant centrality • and pT dependence • at pT> 50 GeV/c Harald Appelshäuser, Quark Matter 2011, Annecy, France

  16. charged particle RAA – centrality dependence • low pT: • approximate scaling • with multiplicity density, • matching also RHIC • results Harald Appelshäuser, Quark Matter 2011, Annecy, France

  17. charged particle RAA – centrality dependence • high pT: • weak suppression, • no significant centrality • dependence • low pT: • approximate scaling • with multiplicity density, • matching also RHIC • results Harald Appelshäuser, Quark Matter 2011, Annecy, France

  18. charged particle RAA - models • pronounced pT dependence • of RAA at LHC • sensitivity to details of the energy loss distribution Harald Appelshäuser, Quark Matter 2011, Annecy, France

  19. reaction plane dependent RAA Talk: A Dobrin Harald Appelshäuser, Quark Matter 2011, Annecy, France

  20. particle identification: dE/dx Talk: A Kalweit π • almost constant separation of pions to K, p above p = 3 GeV/c Harald Appelshäuser, Quark Matter 2011, Annecy, France

  21. pion identification at high pT Poster: P. Christiansen from TPC dE/dx Harald Appelshäuser, Quark Matter 2011, Annecy, France

  22. charged pion fraction • no centrality dependence of pion-to-charged ratio for pT > 6 GeV/c Harald Appelshäuser, Quark Matter 2011, Annecy, France

  23. charged pion spectra • charged pion spectra • out to pT = 20 GeV/c Harald Appelshäuser, Quark Matter 2011, Annecy, France

  24. charged pion RAA • agrees with charged particle RAA • - in peripheral events • - for pT > 6 GeV/c • is smaller than charged particle RAA for pT < 6 GeV/c Harald Appelshäuser, Quark Matter 2011, Annecy, France

  25. secondary vertex reconstruction e+ e- π0  γγ  e+e-e+e- Λ  π- p K0s  π+π- e+ e- Harald Appelshäuser, Quark Matter 2011, Annecy, France

  26. photon conversions Talk: K. Reygers • ALICE material budget (11.4% X0up to middle of TPC) • agrees within +3.4%/-6% with its implementation in GEANT Harald Appelshäuser, Quark Matter 2011, Annecy, France

  27. π0 spectra in pp and Pb-Pb Talk: G. Balbastre Harald Appelshäuser, Quark Matter 2011, Annecy, France

  28. π0 - RAA: comparison to π++ π-- RAA • good agreement • between charged pion • and π0 -RAA Harald Appelshäuser, Quark Matter 2011, Annecy, France

  29. π0 - RAA: comparison to charged particle RAA • good agreement • between charged pion • and π0 -RAA • compatible with charged • particle RAAin • peripheral events • is lower in central • events at • 2 < pT < 5 GeV/c Harald Appelshäuser, Quark Matter 2011, Annecy, France

  30. Λ and K0s -RCP • K0s - RAA very similar to that of • charged particles: • strong suppression of K0s at • high pT • Λ - RAA significantly larger than • charged at intermediate pT: • enhanced hyperon production • counteracting suppression • for pT > 8 GeV/c, Λ and K0s - RAA • similar to charged particle RAA: • strong high-pT suppression also • of Λ Talk: S. Schuchmann Harald Appelshäuser, Quark Matter 2011, Annecy, France

  31. Λ -RCP: comparison to RHIC • K0s - RAA very similar to that of • charged particles: • strong suppression of K0s at • high pT • Λ - RAA significantly larger than • charged at intermediate pT: • enhanced hyperon production • counteracting suppression • above 8 GeV/c, Λ and K0s - RAA • are similar to charged: • strong high-pT suppression also • of Λ • Λ enhancement reaches out • to higher pT than at RHIC • magnitude of RCPcompatible Harald Appelshäuser, Quark Matter 2011, Annecy, France

  32. Λ and K0s - RAA • high-pT: suppression of Λ and K0s similar to charged particles • intermediate pT: moderate enhancement in peripheral collisions •  central RAA similar to RCP Harald Appelshäuser, Quark Matter 2011, Annecy, France

  33. Λ and K0s - RAA: comparison to RHIC • strong nuclear enhancement of Λ observed at RHIC not seen at the LHC Harald Appelshäuser, Quark Matter 2011, Annecy, France

  34. summary • charged particle pT spectra in Pb-Pb at √sNN = 2.76 TeV measured • with ALICE at the LHC • new reference pT spectrum derived from pp collisions at √s = 2.76 TeV • strong suppression charged particle production observed at pT < 50 GeV/c • comparison to RHIC data suggests that suppression scales with the • charged particle density • at pT > 50 GeV/c, no strong centrality dependence of charged particle • production is observed • results on identified particles will allow to disentangle the interplay • between quark and gluon energy loss, and recombination mechanisms • at intermediate pT Harald Appelshäuser, Quark Matter 2011, Annecy, France

  35. Harald Appelshäuser, Quark Matter 2011, Annecy, France

  36. comparison ALICE-CMS Harald Appelshäuser, Quark Matter 2011, Annecy, France