Photon-Photon Interactions: What Determines Pair Production vs. Scattering?

[kuartus4]

When two high energy photons collide with each other, what determines whether a pair production results or whether a photon-photon scattering results? I hope my question makes sense.

 

[mfb]

It is random (and most of the time, nothing happens), as all collisions in particle physics.
Pair production requires at least 1 MeV center of mass energy, of course.

 

[kuartus4]

So a collision that can result in pair production can just as well result in scaterring, with no reason why one occurs and not the other?

 

[Bill_K]

So a collision that can result in pair production can just as well result in scaterring, with no reason why one occurs and not the other?

That's what the man said.

 

[kuartus4]

That's what the man said.

Just checking. I thought there was more to it than that.

 

[Nabeshin]

So a collision that can result in pair production can just as well result in scaterring, with no reason why one occurs and not the other?

This is not to say that they're equally probable though.

In particular, the diagram involving pair production is at tree level whereas the interaction term is one loop.

 

[andrien]

Just checking. I thought there was more to it than that.

you can just use the mandelstam variable S(there are three) which represents total energy to decide which one has more possibility over other.for scattering in which S<< 4m_l²,the cross section σ=α⁴S³/m_l⁸,for box graph.and for
S>> 4m_l²
for single pair production,
σ≈(∏α²/S)log(s/m_l²)