n. the branch of particle physics which studies collisions of particles accelerated to such high energy that new fundamental particles are generated in the process. The creation of new particles of very high energy is required to permit the study of the most fundamental relations between forms of matter, so as to understand the fundamental nature of matter. The high energies also reproduce the high-temperature conditions at the earliest phase of the big bang, allowing generation of some data relevant to understanding the nature and evolution of the universe. [ PJC ]