Comparison of MCEEP and SIMC using a Small Collimator in each simulation
In order to check the two simulations and make comparisons without worrying about any differences in spectrometer models, I did simulations with radiation on and off using a small collimator model in each. The collimator I used was placed 110.9 cm from the target and was +/- 2.218 cm in vertical extent and +/- 1.109 cm in horizontal extent. For MCEEP, the collimator model is included in the input file, whereas for SIMC, it is hard-coded into the spectrometer model subroutine.
After changing the form factor models to be the same in both simulations, they were run in the same modes for both radiation (and all energy losses) on and off. The ratios of integrated yield for MCEEP/SIMC were,
- NO radiation or energy loss: ratio = 1.02
- Radiation ON; ratio = 1.04
As can be seen in the W2 distribution, the tails of both simulations with radiation on are in pretty good agreement; MCEEP is the black trace; SIMC is the green (radiated) or red (non-radiated) trace. The plots of some HRS variables (in-plane, out-of-plane and scattering angles, delta-P etc.) again show good agreement. The differences between the simulations at the edges of the in-plane and out-of-plane angles in the spectrometer might be due to differences in the apertures in the spectrometer models - this is still an open issue that needs more investigating .
The non-radiated W2 distributions show a resolution difference as SIMC is more smeared than MCEEP; again this difference lies in the details of the two codes.
The full encapsulated postscript versions of the plots shown are available here:-