Simulated liquid argon interactions with neutrons

Abstract

The GEANT4 physics simulation program is known to have errors in how hadronic interactions are implemented. This has the potential to cause errors in the Monte Carlos used to determine the expected neutron backgrounds in the MiniCLEAN single phase liquid argon WIMP detector. Elastic and inelastic collisions between neutrons and argon nuclei as well as neutron captures were simulated independently in order to characterize the accuracy of the implementation by GEANT4.9.3.pOl and GEANT4.9.5. The effective cross sections, angular distributions, photons, decay schemes, energy conservation, and momentum conservation were determined through analysis of the neutron tracks created by GEANT4. A large proportion of the interactions behave as expected, however energy and momentum are not conserved by varying degrees of severity with some GEANT4.9.3.pOl inelastic collisions resulting in over twice the correct amount of energy.