Im($\eta _{000}$) = Im($\boldsymbol A$( ${{\boldsymbol K}_S^0}$ $\rightarrow$ ${{\boldsymbol \pi}^{0}}{{\boldsymbol \pi}^{0}}{{\boldsymbol \pi}^{0}}$ )/$\boldsymbol A$( ${{\boldsymbol K}_L^0}$ $\rightarrow$ ${{\boldsymbol \pi}^{0}}{{\boldsymbol \pi}^{0}}{{\boldsymbol \pi}^{0}}$ ))
INSPIRE search
${{\mathit K}_S^0}$ $\rightarrow$ ${{\mathit \pi}^{0}}{{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ violates $\mathit CP$ conservation, in contrast to ${{\mathit K}_S^0}$ $\rightarrow$ ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \pi}^{0}}$ which has a $\mathit CP$-conserving part.