Picture 5.
We can use picture 1 and 2 for this as an analogy. We imagine now, what would happen if there would exist only left-handed electrons and right-handed positrons. Afterwards we replaced the electron by the neutrino.
C only for the passage of pic.1a to pic.1c has been prohibited: left-handed anti neutrinos do not exist.
PC combination for the passage of pic.1a to pic.1c has been permitted: right-handed anti-neutrinos surely exist.
P only for the passage of pic.2a to pic.2b has been prohibited: right-handed neutrinos do not exist.
CTP combination for the passage of pic.2a to pic.2d has been permitted: right-handed anti-neutrinos surely exist.
Back to Space-time diagrams.