Observation of the CP-conserving $K_{S} \rightarrow \pi^{+}\pi^{- }\pi^{0}$ decay amplitude

The interference between CP-conserving $\ks$ and $\kl \rightarrow \threepi$ decay amplitudes was observed by studying the decay rate asymmetries between initial $\ko$ and $\kob$ separately for the phase space regions $E_{\mbox{\rm \scriptsize CM}}(\pi^+)> E_{\mbox{\rm \scriptsize CM}}(\pi^-)$ and $E_{\mbox{\rm \scriptsize CM}}(\pi^+)< E_{\mbox{\rm \scriptsize CM}}(\pi^-)$. For the parameter $\lambda$ we found $\mbox{\rm Re}(\lambda )=0.036\pm0.010(\mbox{\rm stat.}) ^{+0.002}_{-0.003} (\mbox{\rm syst.)}$ and $\mbox{Im}(\lambda)$ consistent with zero, leading for the CP-conserving $\ks \rightarrow \threepi$ decay, to a branching ratio $\mbox{\rm B} = \left[4.1 ^{+2.5}_{-1.9 } (\mbox{\rm stat.}) ^{+0.5} _{-0.6} (\mbox{\rm syst.)}\right] \times 10^{-7}$.