Search for the K_S → 3π⁰ decay with the KLOE detector

Institute of Physics, Jagiellonian University, PL-30-059 Cracow, Poland

^a e-mail: Michal.Silarski@lnf.infn.it

Abstract

The K_S → 3π⁰ decay is a pure CP violating process which, assuming CPT invariance, gives access to the CP – violating phase of the weak decay amplitude into I=1 final states. This decay has not been observed so far, and the best upper limit on the branching ratio BR(K_S → 3π⁰) < 1.2 · 10⁻⁷ is two orders of magnitude larger than predictions based on the Standard Model. In this article we present the search for the K_S → 3π⁰ decay performed with the KLOE detector operating at the DAΦNE ϕ – factory at the Frascati Laboratory. We describe the analysis techniques used for the background rejection and signal events selection leading to the result of an almost five times lower upper limit on the K_S → 3π⁰ branching ratio. We also discuss the perspectives for a new measurement using the KLOE – 2 apparatus equipped with a new inner tracker and the calorimeters at low θ angle.