The ALICE Cosmic Ray Physics Program

1
The ALICE Cosmic Ray Physics Program

• Idea to create a task force to study this topic
• PPR volume 2 chapter 6
• Torino, Catania, Bologna, Bari, Mexico
• Starting from these works (2005) and continuing
  the job.
• Some run with cosmic ray trigger in february

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Extensive Air Shower
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Atmospheric muons
Rock composition over Alice
Element H C O Na Mg
Al Si K Ca Fe
0.8 4.3 48.5 0.7 4.2 3.7 21.5
2.3 10.0 4.0

• Nm (Em gt15 GeV)
• Direction
• Energy

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Main topics

• Distribution of muon bundles (composition)
• Measure on inclusive muons (single muon)
• Study of muon interactions in the TPC
• Cosmic ray events correlated with other LHC
  experiment
• Study of the hadronic interaction models

5
First works ? AliRoot

• Update and check the geometry of ACORDE in
  AliRoot
• Test the Alice Environment molasse, hall,
  shafts
• Generate muons at the ground
• Muons for allignment and calibration

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Alice environment
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Different Muon Generation

• Flat muon distribution at fixed energy
• Real inclusive muon generation
• Muon coming from p, Fe primaries for the study of
  c.r. composition

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Tracking muons in the TPC and ITS
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Trigger condition

• Running during standard Alice data taking imposes
  stringent conditions for cosmic trigger
• low trigger rate (few Hz)
• live time constrictions (statistical problems)
• We have to understand the trigger rate with the
  actual ACORDE geometry

10
The Trigger Background

• What is the influence of p-p events on cosmic
  trigger ?
• What is the influence of p-gas interactions on
  cosmic trigger
• Answered only the first question with old
  geometry
• simulation of 2000 p-p events MB _at_ 14 TeV
  (kPythia6 in Config.C) using AliRoot 4.02
• measure particles in a 5x5 m2 above the magnet
• Only about 3 of events have charged particle
  background above the magnet

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Conclusions

• Task force to start cosmic ray physics
• Insert and check in AliRoot
• ACORDE geometry, ALICE environment, Muon
  generations, Tracking in TPC and ITS
• Alignment and Calibration (are in progress)
• The Trigger conditions
• Start physics topics and more refinated studies
  (inclusive muon, composition, point sources .)
• People interested are welcome