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2

There is not, because the combined transformation $CPT$ is a symmetry of all Lorentz-invariant systems. The $P$-violating decay distribution observed by Wu et al. is also a $C$-violating distribution, because polarized anti-cobalt would have had the opposite sign of asymmetry. (However no one has ever made, or probably will ever make, polarized anti-cobalt,...


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The QCD Lagrangian that has a CP violating symmetry is $$ {\cal L}~=~-\frac{g^2}{4}F_{ab}F^{ab}~-~\frac{g^2\theta}{4} {F_{ab}}^* F^{ab}~+~\bar\psi(i\gamma^a D_a~-~me^{i\gamma_5\theta})\psi $$ where the angle $\theta$ is the chiral phase and a field that mixes fields. It is even proposed to look for this angle or field in its mixing of electromagnetic $\vec E$...


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The simple answer to your question will be to just say that this is due to the non-perturbative effects of the QCD vacuum. As you rightly said in QED, the term $F\cdot \tilde{F}$ doesn't contribute anything - since it is a total divergence, hence no observable consequence in equation of motion simply because this surface term vanishes at spatial infinity. ...



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