Neutron-antineutron oscillation and parity and CP symmetries

Understand

It is shown that the neutron-antineutron oscillation per se does not necessarily imply CP violation in an effective local Lorentz invariant description of the neutron which preserves CPT, contrary to a recent analysis in the literature.

• A CP- and baryon number-violating term can be transformed into a CP conserving one, thus rendering the CP violation spurious and unusable in the analysis of baryogenesis, for example.
• It is also shown that the neutron-antineutron oscillation in a $\Delta B=2$, Lorentz and CPT invariant interaction can occur only when parity is violated, irrespective of the CP properties; when parity is conserved, it is the ordinary quantum transition from neutron to antineutron which takes place.
• Those statements are proven by explicitly analyzing all the possible combinations with P, C and CP violation or their conservation.