1. Detection of atmospheric muon bundles using ALICE detectors A. Fernández Tellez Universidad Autonoma de Puebla for the ALICE Collaboration VIII Simposio Latinoamericano de Física de Altas Energías - SILAFAE 2010 Valparaíso, Chile Dec. 10th 2010

2. Detection of atmospheric muon bundles using ALICE detectors M. Rodríguez, A. F. (BUAP) B. Alessandro, M. A. Zubieta (Torino) V. Canoa (Cinvestav) E. Cuautle (UNAM)

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

4. Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010 ALICE experimental hall during assembly

5. Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010 ALICE subsystems Detectors used for cosmics in the central part : Trigger : ACORDE, TOF, SPD, Tracking : TPC Detectors used for horizontal muons : Trigger Muon Chambers Tracking Muon Chambers

6. Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010 Outline  Muons with central detectors : August-Sept, 2009, Feb. 2010  Triggers: SPD, TOF, ACORDE  Tracking : TPC  Angular distribution  Muon multiplicity distribution  Momentum resolution analysis  Momentum spectrum  Muons with muon spectrometer : August-Sept, 2009 Trigger and Tracking Event and selection Momentum spectrum - Final Remarks

7. Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010 Trigger detectors SPD : triggers when a muon crosses two layers of SPD detector: SCO. ACORDE : 60 scintillators Trigger coincidence of two scintillators : AMU or SL0 (Multi and Single Muon Trigger) 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)

8. Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010 ACORDE ACORDE geometry scheme

9. Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010 TOF The TOF detector covers an effective area for all φ and 45 ≤ θ ≤ 135. This area is around 160 m 2. It will identify charged particles. Temporal resolution < 100 ps Efificiency > 95 %

10. Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010 TOF TOF trigger TOF clusters (magnetic field: 0.5 T) TOF clusters (magnetic field: 0 T) Tracks reconstructed by the TPC

11. Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010 Tracking detector and type of events Muon Interaction Event Standard Muon Event (multimuon) 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).

12. A muon is reconstructed by the TPC as two tracks : up, down up down A matching algorithm connects track up with down to count one muon The momentum is given for the two tracks : Pup and Pdown Single muon Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

13. 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| < 165 cm DeltaDist < 2 cm for matching Tested with real multimuon events (up to 200 tracks) Algorithm for matching TPC tracks Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

14. # RunTime [h] # Events OB3 OCP AMU # Events Mu > 0 OB3 OCP AMU Purity Rate OB3 [Hz] Purity Rate OCP [Hz] Purity Rate AMU [Hz] # Interaction Events # Multi- Mu Events 838119.4834225997198322010.03152 837751.2758092514866630.11.80.052919 838021.053829858183020.51.10.031815 841486.42720090682773281.60.0410398 842054.5168117142433124.71.40.048476 8425472330994587554221.30.039981 843892.2359972315164217.810.033334 844205.12195877649529225.41.40.048092 844554.43 188398247849328.31.60.049882 84479 13779859676125.41.50.041918 84993 1.5246038912029120.71.20.031724 85024 1.3549387012855424.91.40.0418 85031 0.5130487279945412.40.06910 85032 0.431438837592.30.130.00410 85034 113906585102359024.41.40.04197161 Total 57.295223313957880 Run table conditions Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

15. Trigger type distribution Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

16. Muon multiplicity distribution, 4 trigger types Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

17. MMD: TOF single and cosmic Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

18. C Side A Side Zentih & Azimuth Angles for Cosmics x Azimuth Angle C Side A Side Zenith Angle y z muon Z Y X Angular distributions Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

19. Zenith and azimuth distribution of muons Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

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

21. : From simulation studies we see that the measurement of the momentum using the fit of the whole muon track length (Pcov) instead of using up and down separately (Pweight) improve the resolution by a factor ~ 3. : Resolution at 100 GeV/c ~ 50% using up and down separately (Pweight) Resolution at 100 GeV/c ~ 20% using the whole muon track length (Pcov) Muon momentum resolution with data Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

22. Vertical muons 0 o <Teta<20 o Estimated error around 20% at P=100 GeV/c using Pcov. Uncorrected muon momentum distribution Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010

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

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

25. Main Characteristics : Event with 182  Mean Zenith Angle : 40° Mean Azimuth Angle : 212° Density of muons : 12  /m 2 Mean Momentum : 123 GeV/c

26. Main Characteristics : Event with 89  Mean Zenith Angle : 41° Mean Azimuth Angle : 69° Density of muons : 6  /m 2 Mean Momentum : 189 GeV/c

27. Arturo Fernández Téllez - Dec. 10th. 2010, SILAFAE 2010 Ratio World ratio ~ 1.3, P < 100 GeV/c ALICE uncorrected ratio ~1.31, P < 100 GeV/c

28. Θ y negative Θ y positive Muon momentum threshold ~ 4GeV/c (due presence of absorbers) Length detector ~ 17 m (from the interaction point) Length detector ~ 13 m (from first tracking station) Study of horizontal muons

29. Runs of August and September 2009 Total time ~ 240 h → 10 days Magnetic field → 0.5 T N. Total Events → 200372 N. Events with at least one muon → 8194 N. Good events (selected) → 5876 Data sample

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

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

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

33. Uncorrected Muon Momentum Distribution (70 0 -80 0 ) ALICE LEVEL SURFACE LEVEL

34. 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  +/  - for vertical muons with the central detectors (0 0 -20 0 ) and for horizontal muons with muon spectrometer (70 0 -80 0 ) in progress. Study and search of events of very high muon multiplicity can be a test for hadron interaction models