QCD theta angle
= QCD theta angle
{c}
{title2=$\bar\theta$}
The physical <QCD theta angle> is $\bar\theta=\theta_{\rm QCD}+\arg\det(M_uM_d)$. An anomalous chiral quark <rotation> shifts the two terms oppositely, so only their sum is invariant.
= QCD theta angle
{c}
{title2=$\bar\theta$}
The physical <QCD theta angle> is $\bar\theta=\theta_{\rm QCD}+\arg\det(M_uM_d)$. An anomalous chiral quark <rotation> shifts the two terms oppositely, so only their sum is invariant.