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
Cluster (physics) Cluster (physics) In physics, the term clusters denotes small, multiatom particles. As a rule of thumb, any particle of somewhere between 3 and 3×10 atoms is considered a cluster. Two-atom particles are sometimes considered clusters as well. A two atom particle may also be a molecule. The term can also refer to the organization of protons and neutrons within an atomic nucleus, e.g. the alpha particle (also known as "α-cluster"), consisting of two protons and two neutrons (as in a helium nucleus). Although first reports of cluster species date back already to the 1940s, cluster science emerged as a separate