Validation of the Simulation of Collision Events at the LHC

The procedures of validating simulation of particle physics events at the LHC are summarized. Because of the strongly fluctuating particle content of LHC events and detector interactions, particle based Monte Carlo methods are an indispensable tool for data analysis. Simulation in particle physics is founded on factorization and thus its global validation can be realized by validating each individual step in the simulation. This can be accomplished by adopting results of previous measurements, in - situ studies and models. Important in particle physics is to quantify how well simulation is validated such that a systematic uncertainty can be assigned to a measurement. The simulation is tested for a wide range of processes and agrees with data within the assigned uncertainties.