Form factor (quantum field theory)

In quantum field theory (QFT), the term "form factor" refers to a function that describes the dependence of a scattering amplitude on the momentum transfer between particles. Form factors are used to quantify the internal structure of particles, such as hadrons (e.g., protons and neutrons), especially in processes like scattering and decay. Form factors arise when one is dealing with processes that involve composite particles, where the constituent particles do not interact in a simply point-like manner.