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Simulation codes for the neutron-deuteron breakup experiment at 16.0 and 19.0 MeV at the Triangle Universities Nuclear Laboratory (TUNL) are being developed as part of the CREST sub-project 2 computational effort in support of low-energy few-body nuclear physics experiments. The neutron-deuteron (nd) breakup cross-section data at incident neutron energies of 16.0 and 19.0 MeV were recently acquired using the accelerator facility at the Triangle Universities Nuclear Laboratory (TUNL) located on the Duke University campus in Durham, NC. Those data were taken at coplanar-star (CS) and space-star (SS) configurations to study the space-star anomaly in nd breakup. In this experiment, the neutron beam is incident on a deuteron target (CD2 foil). We detect one of the neutrons from the breakup event in a neutron detector in coincidence with the scattered proton in the detector telescope (energy, E, and ?E detectors) in the proton arm.

Theoretical calculations of the cross sections are performed using the ideal conditions of particles detected with 100% efficiency at a single point in space, referred to as a point-geometry calculation. To compare the theory to our measured cross sections performed with realistic detectors that have a finite solid angle acceptance, the point-geometry calculation results [Glo96] need to be smeared over the detector solid angle acceptances. A simulation code that represents the target and detector configuration is therefore needed in order to compare measured data to the theoretical calculations.

We are developing two such codes to simulate this nd breakup experiment. One is a FORTRAN computer language version based on a “home-built” program written at TUNL and the other is constructed using the GEANT4 code package. GEANT4 is a C++ computer language based Monte Carlo code developed by physicists at the European Center for Nuclear Research (CERN) to model particle interactions in target and detector configurations [S. Agostinelli et al. (GEANT4 Collaboration) Nucl. Inst. Meth. A 506, 250 (2003)]. Our goal is to have two working simulation codes for this experiment to evaluate our data and the apparatus.