Machine induced backgroung in pp collision mode

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Machine induced backgroung in pp collision mode

• ALICE dimuon Meeting
• Le Mont Dore
• 25/03 29/03
• Rachid GUERNANE
• IPN Orsay

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Overview

• Introduction
• Sources of beam-related background
• Simulation
• Fluxes in trigger chambers

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Introduction

• Proton losses up(down)stream of the IP induce
  fluxes of secondary particles
• affect the radiation environment in the
  corresponding IR
• detector background
• Machine induced background is proportional to the
  beam current while particle fluxes produced in pp
  collisions scale with luminosity at IP
• relative effect of MIB
• depend on machine operating conditions
• is different for different run scenarios

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Sources of the MIB

• Secondary particles cascades can be initiated in
  the IR
• (In)elastic beam particles scattering on
• machine elements
• residual gas in the vacuum pipe (H, O and C)
• Cleaning inefficiency
• pp collisions in high luminosity IP
• give energetic protons transported to and
  lost in the next IR

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Details of simulation

• Original proton interactions with the nucleus of
  the residual gas were simulated along the whole
  length of the LHC Ring sectors at
• New gas pressure estimates (LHC Project Note 273)
• All types of possible beam proton losses in the
  corresponding sectors of LHC were included in the
  simulations
• Transport of secondaries
• overall threshold of 20 MeV on the particle
  kinetic energy
• High energy hadrons and muons are considered
• main component (critical to the detector
  performance)
• component (and as well) not studied

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ALICE Simulation Framework

• AliRoot v3-07-04 with ROOT v3-02-07
• AliGenHaloProtvino event generator
• input file in ASCII format containing the result
  of the calculation of the muon beam halo at
• muons coming from both sides
  
• Set-up configuration
• L3 magnet
• exp. hall
• central detectors ITS, TPC
• muon spectrometer
• V0R detector

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Muon background at
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Hadronic background (charged)
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Fluxes in Trigger Chamber 1
Only muons
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Flux in Trigger Chamber 1
All particles
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Fluxes in Trigger Chamber 1
all particles
only muons
Both sides