Search for CP violation in K0 --> 3 pi(0) decays

Using data taken during the year 2000 with the NA48 detector at the CERN SPS, a search for the CP violating decay KS→3π0 has been performed. From a fit to the lifetime distribution of about 4.9 million reconstructed K-0/K-0bar→3π0 decays, the CP violating amplitude η000=A(KS→3π0)/A(KL→3π0) has been found to be Re(η000)=−0.002±0.011±0.015 and Im(η000)=−0.003±0.013±0.017. This corresponds to an upper limit on the branching fraction of Br(KS→3π0)<7.4×10−7 at 90% confidence level. The result is used to improve knowledge of Re(ε) and the CPT violating quantity Im(δ) via the Bell–Steinberger relation.