[phkahler]

>> Basically two photons with enough energy to interact via virtual pairs created.

Or could it be that a photon bends space-time as though it had mass, and they simply follow the local curvature and it looks like scattering? Just speculating, because for some purposes photons act like a solid particle with their energy equivalent mass traveling at speed c.

[jessriedel]

It is not gravitational. That effect would be far, far too weak.

[Florin_Andrei]

For that to happen, the energy-equivalent of the photons would have to be close to the Planck mass. That's an unbelievably high value for photons. We're not going to see that reproduced experimentally any time soon.