This is the $\mathit CP$-violating asymmetry
$\mathit A$= ${\mathit N_{{\mathrm {sin\phi~}}{\mathrm {cos~\phi~}}>0.0}−\mathit N_{{\mathrm {sin\phi~}}{\mathrm {cos~\phi~}}<0.0}\over \mathit N_{{\mathrm {sin\phi~}}{\mathrm {cos~\phi~}}>0.0}+\mathit N_{{\mathrm {sin\phi~}}{\mathrm {cos~\phi~}}<0.0}}$
where $\phi $ is the angle between the ${{\mathit e}^{+}}{{\mathit e}^{-}}$ and ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ planes in the ${{\mathit K}_L^0}$ rest frame.