Time direction and CP symmetry breaking

In 1957 it was proved that the P symmetry is broken in the beta decay of 60Co. The same year it was also proved that the P and C symmetry are broken in the decay of charged pions. The CP violation was discovered for the first time in 1964 in kaon systems, this discovery implied automatically the breaking of the T symmetry because of the Lorentz invariance principle that imposes the CPT symmetry for all systems. A direct confirmation of the violation of the T symmetry was acquired in 1998 through the study of the decay of kaons and anti-kaons. It appears that the CP symmetry is described by one parameter in the standard model and is linked to the existence of 3 families of quarks. The T symmetry breaking seems to be linked to the difference of behaviour between a particle and its anti-particle counterpart. (A.C.)