Energy loss in a specific process

I am now investigating what happens when a photon enters a detector.
There is a problem that the energy is not conserved, so I am comparing the energy before and after the step.
I’m thinking the photon passed all its energy to the neutron and so on and then disappeared.
However, I am struggling because there is no way to prove my thoughts.
If anyone knows how, please help. Thanks.

In photoNuclear, the photon is absorbed by a nucleus (not a neutron); that’s why it goes to zero energy. The nucleus then emits a neutron, or maybe a proton, or something else if the photon is energetic enough.

First of all, thank you for reply.
I totally agreed with you, but the name of the particle I’m saving now is the particle after reaction.
Also, even if the photon gave energy to the nucleus, it could not find that energy.

I triedto check the deposit energy or sum the energy of the particles produced after the reaction.
Is there anything I missed?

There should have been either an EnergyDeposit recorded, or (if you have the “proton cut” set to zero) the recoiling nucleus should have shown up as a secondary. Do you see the neutron (or a proton, or whatever) as an outgoing secondary from the interaction?