It is known that high energy gamma photons can decay into electron-positron pairs in a strong background field via the multi-photon Breit-Wheeler process. This real photon is first emitted by an energetic electron, therefore this is a two-step process. There exist also one-step process, where the intermediate photon is virtual, thus one electron can directly create the pair in a strong laser field. For the trident production rate I found formulas in the literature, which is implemented in EPOCH for instance, but in the code the energy of newly created particles is zero. In the case of two-step process it is clear that the total energy of pair is equal to the photon energy, but I could not find any clear expression for this initial energy in the case of trident. I think it is assumed that their initial momentum is relatively small and their recoil effect is negligible, that's why it is approximated by zero in order to reduce the computation in PIC codes. However, I could not find any paper supporting this statement. Can someone help me in this ?