model{
  # particle extracted according to beam composition
  part ~ dbern(p.mu)   # 0: pion; 1: muon

  # 0/1 transformed into valid index 1/2 of vector p.trig  
  # (BUGS does like "p.trig[part + 1]" !)
  part.ind <- part + 1

  # trigger issued (1: YES; 0: NO), depending on particle index 
  T ~ dbern(p.trig[part.ind])
}