Coincidence scoring in ΔE–E detector shifts Residual-E peaks

Dear FLUKA team and community,

I am simulating a ΔE–E detector with an alpha source (three energy peaks). The setup includes:

  • A thin Delta-E (ΔE) detector in front.
  • A thicker Residual-E detector behind it.

I score:

  1. Energy deposition in ΔE.
  2. Energy deposition in Residual-E.
  3. Coincidence: energy in ΔE only when the same particle also hits Residual-E.

Without coincidence, the Residual-E peaks for the alfa show the expected energy loss.
With coincidence active:

I believe this should not happen. Any advice would be very appreciated.

Thank you.

It looks like there is a syntax error in your last two DETECT cards: in order to distinguish between detector and trigger region, you need to input the latter with the minus sign.