Two-photon physics
BRANCH OF PARTICLE PHYSICS CONCERNING INTERACTIONS BETWEEN TWO PHOTONS
Gamma-gamma physics; Photon-photon scattering; Photon–photon scattering; Scattering of light by light; Light-by-light scattering
Two-photon physics, also called gamma–gamma physics, is a branch of particle physics that describes the interactions between two photons. Normally, beams of light pass through each other unperturbed.