Breit frame

In particle physics, the Breit frame (also known as "brick wall" frame or infinite-momentum frame) is a frame of reference used to describe scattering experiments of the form A + B → A + ∑ C i , that is experiments in which particle A scatters off particle B, possibly producing particles C i in the process. The frame is defined so that the particle A has its momentum reversed in the scattering process.