Derivation and quantitative analysis of the differential   self-interrogation Feynman-alpha method
  A stochastic theory for a branching process in a neutron population with two energy levels is used to assess the applicability of the differential self-interrogation Feynman-alpha method by numerically estimated reaction intensities from Monte Carlo simulations. More specifically, the variance to mean or Feynman-alpha formula is applied to investigate the appearing exponentials using the numerically obtained reaction intensities. 
Johan Anderson, Lenard Pal, Imre Pazsit, Dina Chernikova and Sara   Pozzi
nucl-ex