Initial and final state radiation
= Initial and final state radiation
{wiki=Initial_and_final_state_radiation}
Initial State Radiation (ISR) and Final State Radiation (FSR) are terms used in particle physics to describe phenomena related to the emission of photons during particle interactions, specifically in high-energy collisions. \#\#\# Initial State Radiation (ISR): - **Definition**: ISR refers to the emission of one or more photons by incoming particles before the primary interaction occurs.