Initial and final state radiation Initial and final state radiation In particle physics, initial and final state radiation refers to certain kinds of radiative emissions that are not due to particle annihilation. It is important in experimental and theoretical studies of interactions at particle colliders. Particle accelerators and colliders produce collisions (interactions) of particles (like the electron or the proton). In the terminology of the quantum state, the colliding particles form the "Initial State". In the collision, particles can be annihilated or/and exchanged, producing possibly different sets of particles, the "Final States". The Initial and Final States of the interaction relate through the so-called scattering
Radiation length beyond leptons and photons, the presence of the stronger hadronic and nuclear interaction makes it a far less interesting characterisation of the material; the nuclear collision length and nuclear interaction length are more relevant. Comprehensive tables for radiation lengths and other properties of materials are available from the Particle Data Group Radiation length In physics, the radiation length is a characteristic of a material, related to the energy loss of high energy particles electromagnetically interacting with it. In materials of high atomic number (e.g. W, U, Pu) the electrons of energies >~10 MeV predominantly lose energy by bremsstrahlung, and high-energy