Upper limit on the $etatopi^{+}pi^{-}$ branching fraction with the KLOE experiment

Based on an integrated luminosity of 1.61 fb$^{-1}$ $e^+e^-$ collision data collected with the KLOE detector at DA$Phi$NE, the Frascati $phi$-factory, a search for the $P$- and $CP$-violating decay $etatopi^{+}pi^{-}$ has been performed. Radiative $phitoetagamma$ decay is exploited to access the $eta$ mesons. No signal is observed in the $pi^{+}pi^{-}$ invariant mass spectrum, and the upper limit on the branching fraction at 90% confidence level is determined to be ${mathcal B}(etatopi^{+}pi^{-})<4.9times10^{-6}$, which is approximately three times smaller than the previous KLOE result. From the combination of these two measurements we get ${mathcal B}(etatopi^{+}pi^{-}) < 4.4times10^{-6}$ at 90% confidence level.