U-238 fission yield

Hi,

I want to evaluate the fission yield from 40 MeV proton on U-238 (more
precisely, a UC compound).
As you can see from the attached picture, I get reasonable results, even
compared to MCNPX data, but I cannot explain where does the central peak
come from, I mean the one corresponding to A=115.
I thought this fission yield shape was typical for higher proton
energies, while for 40 MeV protons I would expect a 'valley' in that
region (110 < A < 120).
The other question I have, is it possible to score just fission products
excluding nuclei emerging from other reactions?
Thanks a lot

Lucia