A new limit on the CP violating decay KS→3π0 with the KLOE experiment

We have carried out a new direct search for the CP violating decay KS -> 3pi0 with 1.7 fb^-1 of e+e- collisions collected by the KLOE detector at the phi-factory DAFNE. We have searched for this decay in a sample of about 5.9 x 10^8 KS KL events tagging the KS by means of the KL interaction in the calorimeter and requiring six prompt photons. With respect to our previous search, the analysis has been improved by increasing of a factor four the tagged sample and by a more effective background rejection of fake KS tags and spurious clusters. We find no candidates in data and simulated background samples, while we expect 0.12 standard model events. Normalizing to the number of KS -> 2pi0 events in the same sample, we set the upper limit on BR(KS -> 3pi0 < 2.6 x 10^-8 at 90% C.L., five times lower than the previous limit. We also set the upper limit on the eta_000 parameter, |eta_000 | < 0.0088 at 90% C.L., improving by a factor two the latest direct measurement. We have carried out a new direct search for the CP violating decay K_S->3@p^0 with 1.7 fb^-^1 of e^+e^- collisions collected by the KLOE detector at the @F-factory DA@FNE. We have searched for this decay in a sample of about 5.9x10^8K_SK_L events tagging the K_S by means of the K_L interaction in the calorimeter and requiring six prompt photons. With respect to our previous search, the analysis has been improved by increasing of a factor four the tagged sample and by a more effective background rejection of fake K_S tags and spurious clusters. We find no candidates in data and simulated background samples, while we expect 0.12 standard model events. Normalizing to the number of K_S->2@p^0 events in the same sample, we set the upper limit on BR(K_S->3@p^0)=<2.6x10^-^8 at 90% C.L., five times lower than the previous limit. We also set the upper limit on the @h_0_0_0 parameter, |@h_0_0_0|=<0.0088 at 90% C.L., improving by a factor two the latest direct measurement.