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The Performance of the ALICE experiment for cosmic ray physics

The Performance of the ALICE experiment for cosmic ray physics. B. Alessandro , V. Canoa, A. Fernández, M. Rodríguez, M. Subieta for the ALICE Collaboration. ALICE Experiment at LHC. ALICE located 40 m. underground 30 m of rock (molasse) 10 m of air Threshold Muon Energy ~ 15 GeV.

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The Performance of the ALICE experiment for cosmic ray physics

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  1. The Performance of the ALICE experiment for cosmic ray physics B. Alessandro, V. Canoa, A. Fernández, M. Rodríguez, M. Subieta for the ALICE Collaboration

  2. ALICE Experiment at LHC ALICE located 40 m. underground 30 m of rock (molasse) 10 m of air Threshold Muon Energy ~ 15 GeV

  3. ALICE Experiment during assembly

  4. Detectors used for cosmics in the central region : Trigger : ACORDE, TOF, SPD Tracking : TPC Detectors used for horizontal muons : Trigger Muon Chambers Tracking Muon Chambers

  5. Study of the cosmic runs taken during Summer 2009 and February 2010 • Data Summer 2009 • Muons with central detectors • Triggers: SPD, TOF, ACORDE Tracking : TPC • Muon multiplicity distribution • Angular distribution • Momentum and Ratio m+/m- (vertical muons 0o-20o) • Muons with forward muon spectrometer • Trigger and Tracking • Type of events and selections • Momentum and Ratio m+/m- (horizontal muons 70o-80o) Data February 2010 • Muon Multiplicity Distribution • High Multiplicity events

  6. Trigger Detectors ACORDE : 60 scintillators Trigger coincidence of two scintillators : AMU TOF cylinder of MRPC surrounding the TPC two types of trigger : 1 pad up  1 pad down +- 3 pads : TOF Single (OB3) 4 pads everywhere : TOF Cosmic (OCP) SPD small detector trigger when muon cross two layers : SCO

  7. Tracking Detector and type of events TIME PROJECTION CHAMBER (TPC) : ALICE TPC Collaboration, J. Alme et al., "The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events.", Physics. Ins-Det/10011950 (2010). Muon Interaction Event Standard Muon Event (multimuon)

  8. Single muon A muon is reconstructed by the TPC as two tracks : up , down up up down down A matching algorithm connects track up with down to count one muon The momentum is given for the two tracks : Pup and Pdown

  9. Algorithm for matching TPC tracks • Find parallel tracks, match the TPC tracks, count the muons (single TPC track, matched TPC tracks) • N. TCP clusters > 30 (matched tracks) • N. TPC clusters > 50 (single tracks) • P > 0.5 GeV • Cos(DeltaDirection) > 0.990 • |Z-Zo| < 250 cm |X-Xo| < 250 cm • DeltaDist < 2 cm for matching • Tested with real multimuon events (up to ~ 200 muons)

  10. Reconstruction of CR - events with ACORDE , SPD + TPC Run: 109547 (Feb. 2010) Event: 3723 # of TPC tracks: 182 # of muons: 89 Some TPC tracks fail the N.of cluster cut

  11. DATA TAKING: SUMMER 2009

  12. Trigger Type Distribution

  13. Muon Multiplicity Distribution for the 4 Triggers

  14. Muon Multiplicity Distribution : Data and Simulation Real data 2.5 days live time Estimation 30 days live time

  15. Angular Distributions Zenith Angle y Zenith & Azimuth Angles for Cosmics muon A Side C Side Y z Azimuth Angle x C Side Z A Side X

  16. A SIDE Zenith Angle C SIDE y A Side C Side z Azimuth Angle x SHAFT SHAFT

  17. Uncorrected Muon Momentum Distribution with Pcov Pcov : Momentum obtained fitting the whole track length of the muon (up and down as one track) Vertical muons 0o< Teta<20° No shaft effect Estimated error around 25% at P=100 GeV/c using Pcov

  18. Ratio m+/m- (vertical muons) Alice Uncorr. Ratio~ 1.31 P<100 GeV/c World Ratio~ 1.28 P<100 GeV/c

  19. Study of Horizontal Muons with Forward Muon Spectrometer Qy negative Qy positive • Muon momentum threshold ~ 40GeV/c (due to the rock) • Detector length ~ 17 m (from the interaction point) • Detector length ~ 13 m (from first tracking station)

  20. Data Sample • Runs of August and September 2009 • Total time ~ 216 h → 9 days • Magnetic field → 0.7 T • N. Total Events → 200372 • N. Events with at least one muon → 8194 • N. Good events (selected) → 5876

  21. Variables for Horizontal Muons y y ThetaY ThetaY < 0 y ThetaY > 0 muon z z ThetaY = arctg(Py/Pz) Zenith Cosmic = 90o - |ThetaY| ThetaX = arctg(Px/Pz) A Side C Side z Y ThetaX x Z A Side C Side X

  22. Selection of good events Cut to select “good events” : ThetaY > 0  5876 events

  23. Angular Distributions and Selection of the events 70o< Zenith < 80o 5876 events after these cuts  2862 events 85o< Azimuth < 95o

  24. Energy loss from Surface to ALICE Simulation to obtain the energy loss by m+ and m- crossing the rock from Surface to ALICE experiment at different Zenith Angles

  25. Uncorrected Muon Momentum Distribution (700-800) SURFACE LEVEL ALICE LEVEL

  26. Uncorrected Ratio m+/m- at Surface level (700-800)

  27. DATA TAKING: FEBRUARY 2010 Trigger : ACORDE and SPD Time : 2.2 effective days Two events with high muon multiplicity

  28. High Muon Multiplicity Events Simulation Time : 30 effective days Time : 2.2 effective days 89 muons 182 muons

  29. Main Characteristics : Event with 182 m Mean Zenith Angle : 40° Mean Azimuth Angle : 212° Density of muons : 12 m/m2 Mean Momentum : 123 GeV/c

  30. Main Characteristics : Event with 89 m Mean Zenith Angle : 41° Mean Azimuth Angle : 69° Density of muons : 6 m/m2 Mean Momentum : 189 GeV/c

  31. Muon Density and Primary Energy Estimate (Simulation) • A density of 6 m/m2 at ALICE level is obtained with : • Primary with 1016 eV • In the core of the shower 89 muons : 6 m/m2 Eprimary >= 1016eV 182 muons : 12 m/m2 Eprimary > 1016 eV

  32. Final Remarks • ALICE can study atmospheric muons with central detectors (vertical muons) measuring : Num. of muons, Momentum, Charge, Direction. • In the future analysis of the correlations of these quantities for composition studies ???? • Measurement of the Ratio m+/m- for vertical muons with the central detectors (00-200) and for horizontal muons with muon spectrometer (700-800) in progress. • Study and search of events of very high muon multiplicity can be a test for hadron interaction models

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