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ALICE d N ch / dη analysis for the “common plots”

Minimum Bias and Underlying Event Working Group 06-07 September 2010. ALICE d N ch / dη analysis for the “common plots”. C. Zampolli. Outline. INEL > 0 analysis Results at 900 GeV Outlook and Conclusions. INEL>0. Defined as a new class of events…

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ALICE d N ch / dη analysis for the “common plots”

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  1. Minimum Bias and Underlying Event Working Group 06-07 September 2010 ALICE dNch/dη analysis for the “common plots” C. Zampolli

  2. Outline • INEL > 0 analysis • Results at 900 GeV • Outlook and Conclusions C. Zampolli

  3. INEL>0 • Defined as a new class of events… • Selecting the events with at least one particle in |η| < 0.8 and pT > pT, cut • …where the charged multiplicity pseudorapidity density is determined by the number of tracks in the same η and pT range • Tracks in |η| < 0.8 and pT > pT, cut • pT, cut set at 0.5, 1. GeV, for the common plots • In addition, pT,cut at 0.15 GeV considered, as this is ALICE intrinsic pT,cutoff C. Zampolli

  4. Previous Results from ALICE • So far: results obtained counting the tracklets reconstructed in the ITS (6 layer silicon detector) • Using the 2 layers of the SPD detector • No pT measurement (intrinsic cut at about 50 MeV) • Now: full tracking in ALICE required • Using ITS + TPC • pT measurement from 0.15 GeV C. Zampolli

  5. ALICE Tracking arxiv:1007.0719 ALICE Tracking Efficiency ALICE Tracklets Efficiency ALICE Performance pT (GeV/c) SPD physics efficiency for primaries (2009 configuration, 80% active) ALICE full tracking, intrinsic pT cutoff at 0.15 GeV Primary particles = charged particles produced in the collision and their decay products excluding weak decays from strange particles C. Zampolli

  6. all events all events all events no trigger no trigger no trigger no trigger no vertex no vertex no vertex no vertex no vertex The Analysis • Following the same method used for the previous dNch/dη measurements • Basically: to which • Track-to-particle correction • Track level • Vertex reconstruction correction • Track and event level • Trigger bias correction • Track and event level have to be applied From J.F. Grosse-Oetringhaus, Rencontres de Moriond, 14. – 19. March 2010 C. Zampolli

  7. Some Numbers • Number of Events: • Correction Factors: C. Zampolli

  8. Event Selection Efficiency pT > 0.15 GeV pT > 0.5 GeV pT > 1.0 GeV C. Zampolli

  9. Systematic Uncertainties C. Zampolli

  10. dNch/dη, |η|<0.8, pT>0.15 GeV C. Zampolli

  11. dNch/dη, |η|<0.8, pT>0.5 GeV C. Zampolli

  12. dNch/dη, |η|<0.8, pT>1.0 GeV C. Zampolli

  13. Results’ Comparison C. Zampolli

  14. Summary and Conclusions • A new event class definition has been introduced and studied • Event class: INEL>0|η|<0.8, pT > 0.15, 0.5, 1.0 GeV • Tracks: |η|<0.8, pT > 0.15, 0.5, 1.0 GeV • The analysis has been performed in ALICE at √s = 0.9 TeV • Analysis at √s = 7 TeV not yet approved • Different MC seem to agree better with the data at different pT cuts C. Zampolli

  15. Thanks to… • H. Appelshaeuser • A. Dainese • M. Floris • J.F. Grosse-Oetringhaus • J. Otwinowski • F. Noferini • …and many more… C. Zampolli

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