Introduction

The outer space surrounding us and the entire Universe as a whole are filled with high-energy particles of matter—photons, electrons, protons, hydrogen atoms, helium, heavier atoms, the nuclei of which can consist of several tens of nucleons. All of them perform, interacting with each other, as well as with gravitational and electromagnetic fields. In most cases, the particle–particle interactions are treated in terms of collision events, between which the particles move along smooth continuous trajectories. It is in such collisions particles can vanish, being absorbed by other particles, change their momentum being scattered by other particles, and produce new particles, sometimes in rather large numbers (multiple production).