ABSTRACT
A small matter-antimatter asymmetry of the weak force has been experimentally established. This CP violation may be related to the small excess of matter from the big bang. This chapter discusses Kaon decay experiments demonstrating the direct CP violation. In our present universe, we observe with optical telescopes about 100 billion galaxies each of them with 100 billion stars. These stars for most of their life burn hydrogen to Helium, through nuclear fusion. During the big bang, at high temperatures above 10 degrees Kelvin, matter does not consist only of the stable building blocks which we observe in our old and cold universe, the protons and neutrons of the nucleus, and the electrons and neutrinos. In the universe today there is no indication of antimatter left over from the big bang. In the hot fireball, creation and annihilation of particles and antiparticles led to an equilibrium of approximately equal numbers of particles, antiparticles and photons.
