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Background in ALICE: comparison between data and simulation A. Alici

Background in ALICE: comparison between data and simulation A. Alici. Outline. Comparison between data and simulation for charged particles in the ALICE central barrel @ 900GeV and 7TeV Comparison between data and simulation for muons in the Muon Spectrometer @ 7 TeV.

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Background in ALICE: comparison between data and simulation A. Alici

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  1. Background in ALICE: comparison between data and simulation A. Alici LBS meeting

  2. Outline • Comparison between data and simulation for charged particles in the ALICE central barrel @ 900GeV and 7TeV • Comparison between data and simulation for muons in the Muon Spectrometer @ 7 TeV LBS meeting

  3. Reminder: ALICE trigger detectors in the central barrel V0A BEAM1 ITS V0C SPD V0C rin=8 cm rout= 76 cm V0A rin=8 cm rout=100 cm 340 cm 90 cm SPD: silicon pixel detector, 2 innermost layers of Inner Tracking System V0: small angle detector consisting of two arrays of scintillator counters (V0A and V0C). Time spectra allow beam-gas events rejection LBS meeting

  4. Reminder: trigger classes CINT1B  (SPD FO || V0A || V0C) && beam1 && beam2  collisions + beam background + noise CINT1A  (SPD FO || V0A || V0C) && beam1 && (!beam2)  beam background + noise CINT1C (SPD FO || V0A || V0C) && (!beam1) && beam2  beam background + noise CINT1E (SPD FO || V0A || V0C) for fixed “empty” BXs  noise Beam-Background (BG) = CINT1A + CINT1C – 2 CINT1E * * assuming the same bunch intensities for colliding/non-colliding beam1/beam2 LBS meeting

  5. Comparison between data and simulation in the central barrel: SPD clusters Machine Induced Background simulation: simulated beam1 + beam-halo on a scoring plane 20m away from the IP (simulation provided by R. Appleby ), then particles transport, full detector simulation and trigger emulation. The distributions are normalized to the number of events. 900 GeV 7 TeV LBS meeting

  6. Comparison between data and simulation in the central barrel: V0 multiplicity Charged-particle multiplicity distribution @ 900 GeV LBS meeting

  7. Comparison between data and simulation in the central barrel: V0 multiplicity Charged-particle multiplicity distribution @ 7 TeV LBS meeting

  8. Comparison between data and simulation in the central barrel: TPC tracks Pt distribution of reconstructed TPC tracks (loose cuts) @ 7 TeV Outer radius = 250cm Inner radius = 85cm LBS meeting

  9. Comparison between data and simulation: muons Muon Spectrometer -4.0 < η < -2.5 -503cm ≤ z ≤- 90cm BEAM1 LBS meeting

  10. Comparison between data and simulation: muons Muon pt distribution measured with the Muon Spectrometer @ 7 TeV Distribution normalized to number of events, but in real case μ(CINT1A)/ μ(CINT1B) ~ 0.1% LBS meeting

  11. Comparison between data and simulation: muons rapidity distribution @ 7 TeV dca (distance of closest approach ) @ 7 TeV • most of the background comes from beam-halo • background can be treated with ALICE control triggers LBS meeting

  12. Background over CINT1B Fill number 1059 1117 1118 1122 1133 1250 1267 2b_1_1_1 6b_3_3_3 8b_4_4_4 13b_8_8_8 25b_16_16_16 117220 117222 120504 120616 120822 120824 126432 127729 128820 128836 128850 Run number Ratio BG/CINT1B in the range 0.1 – 0.5%; this is not an issue for the analysis with minimum-bias trigger in the central barrel. If we apply the physics selection cuts (see M. Floris, LBS 19/04/2010), the ratio BG/CINT1B goes below 0.1%. LBS meeting

  13. Conclusions and Outlook • Good agreement between data and simulations • Dedicated runs needed to contribute to the cross talk between IPs studies. LBS meeting

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