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