ABSTRACT
Fγ1γ2 = 4p1 · p2 = 4ω1ω2(1− cos θ). (A.2) For collinear beams θ = π, and
Fγ1γ2 = 4p1 · p2 = 8ω1ω2. (A.3) For one photon, p1 = ω(1, kˆ), and one fermion, p2 = E(1, β),
Fγe = 4 p1 · p2 2m
= 2γω(1− β cos θ), (A.4) where γ = E/m. For collinear beams
Fγe = 2γω(1 + β). (A.5)
In the laboratory (LAB) frame β = 0, γ = 1, and
FLABγe = 2ω. (A.6)
For no photons
Fee = 4
√ E21E
2m12m2 = √
γ21γ 2 2(1− β1β2 cos θ)2 − 1.
