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

Extensive Air Shower

Atmospheric muons Nm (Em >15 GeV) Direction Energy 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 >15 GeV) Direction Energy

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

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

Alice environment

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

Tracking muons in the TPC and ITS

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

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 @ 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

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