Geometry Optimization in NOvA with Geant4

NOvA is a neutrino beam experiment, designed to detect neutrino oscillations. There are two detectors, placed at distances of 1km and 810 km from the proton target. The detectors are made of PVC filled with liquid scintillator. In simulating the experiment, an important aspect is the detector geometry, which is input to Geant4 using the GDML markup language. I will present studies in which the geometry description was systematically varied to find a configuration which preserved the modeling accuracy required by the experiment while minimizing the CPU time required for the simulation.