Form factors of elementary particles

Abstract

How BIG ARE the elementary particles? How is their charge distributed? These questions are tackled with form factors, which are measures of the charge and magnetic‐moment distributions in the particles. Scattering of electrons on nucleons, and recent measurements made with electron–positron colliding beams, give form factors for the proton, neutron and pion. The behavior of the pion form factor can be fairly well understood by the “rho‐dominance model,” but the nucleon form factors are not so easy to understand. Different models are currently being examined in an attempt to solve this basic problem in strong‐interaction physics.