why does a photon split into an electron and an antiproton when it strikes a heavy nucleus?

please explain in detail

I think you have got the question wrong there. Photons are packets/quanta of energy. They are not conventional particles like protons or electrons. So they can’t split into them like that.

i am quite sure the q is right

Actually photon does not split into an electron and an antiproton.

But, The neutrino theory of light is the proposal that the photon is a composite particle formed of a neutrino–antineutrino pair. It is based on the idea that emissionand absorption of a photon corresponds to the creation and annihilation of a particle–antiparticle pair. The neutrino theory of light is not currently accepted as part of mainstream physics, as according to the standard model the photon is an elementary particle, a gauge boson.