Im($\eta _{+−0}){}^{2}$ = $\Gamma\mathrm {( {{\boldsymbol K}_S^0} \rightarrow {{\boldsymbol \pi}^{+}} {{\boldsymbol \pi}^{-}} {{\boldsymbol \pi}^{0}} , \boldsymbol CP-violating)}$ $/$ $\Gamma\mathrm {( {{\boldsymbol K}_L^0} \rightarrow {{\boldsymbol \pi}^{+}} {{\boldsymbol \pi}^{-}} {{\boldsymbol \pi}^{0}} )}$
INSPIRE search
$\mathit CPT$ assumed valid (i.e. Re($\eta _{+−0}$) $\simeq{}$ 0).