Decay Process

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Decay Process

• Makoto Asai (SLAC)
• On behalf of Hisaya Kurashige (Kobe Univ.)
• Geant4 Users Workshop _at_ SLAC
• Feb. 19th, 2002

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Decay process

• G4Decay Class is a process which manages
• Decay at Rest
• AtRestDoIt
• mean life time ?
• Decay in Flight
• PostStepDoIt
• mean free path c????
• Decay mode is given by Decay Table Information
• G4DecayTable is a list of G4VDecayChannel.
• G4VDecayChannel describes each decay mode.
• Branching Ratio
• Daughter Particle List
• Decay Kinematics given by DecayIt method

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Decay Channel

• G4VDecayChannel is an abstract class
• Its derived classes are
• G4PhaseSpaceDecayChannel phase space
• G4DalitzDecayChannel p0 dalitz
• G4MuonDecayChannel m -gt e n n decay
• G4KL3DecayChannel Kon semileptonic
• G4NeutronBetaDecayChannel neutron beta decay
• See Physics ReferenceManual for details of
  these decay modes
• Users can easily define his new decay mode

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Class Diagram
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G4DecayGPIL
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G4DecayDoIt
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PreAssignedDecay

• User can assign
• Decay time
• Decay modes
• to each primary track in its rest frame by using
• PreAssignedDecayProperTime
• PreAssignedDecayProducts
• in G4DynamicParticle
• Example Decay by Event Generator
• If daughter particles are written in HEPEVT
  format,
• the parent keeps these information in
  PreAssignedDecayProducts
• Decay time can be set by using G4PrimaryParticle
  SetProperTime()

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Radioactive decay

• Long-term (gt1?s) radioactive decay induced by
  spallation interactions can represent an
  important contributor to background levels in
  space-borne ?-ray and X-ray instruments, as the
  ionisation events that result often occur outside
  the time-scales of any veto pulse.
• The Radioactive Decay Model (RDM) treats the
  nuclear de-excitation following prompt
  photo-evaporation by simulating the production of
  ?, ?-, ?, ? and anti-?, as well as the
  de-excitation ?-rays.
• The model can follow all the descendants of the
  decay chain, applying, if required, variance
  reduction schemes to bias the decays to occur at
  user-specified times of observation.

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Radioactive decay
Ion from G4 tracking defined by A, Z, Q,
nuclear and atomic excitation state
Sample decay profile to determine time of decay.
If stable do not process
User input defines times of observation for
biasing decay curve, splitting of nuclei, and
nuclide decays to ignore
Sample branching ratios
Geant4 Tracking process control
User input defines Biasing of branching ratios
Sample secondaries and commit to stack. Determine
nuclear recoil.
RDM-specific user inputs
a, b, n
Geant4 data sources
Apply photonuclear de- excitation process
g
Geant4 simulation