The upper limit on the $K^+ \to \pi^0\pi^0\pi^0e^+\nu$ decay

TL;DR

This paper reports a search for a rare kaon decay mode, setting a new upper limit on its branching ratio that is significantly lower than previous measurements, using data from the OKA experiment.

Contribution

The study provides the first stringent upper limit on the $K^+ o ext{pi}^0 ext{pi}^0 ext{pi}^0 e^+ u$ decay, improving the previous limit by a factor of 65.

Findings

No signal observed for the decay.

Upper limit on branching ratio set at 5.4×10⁻⁸.

Significantly tighter constraint than previous data.

Abstract

A search for the $K^{+} \to \pi^{0}\pi^{0}\pi^{0}e^+\nu$ decay is performed by the OKA collaboration. The search is based on $3.65 \times 10^9 ~ K^+$ decays. No signal is observed. The upper limit set is $BR(K^{+} \to \pi^{0}\pi^{0}\pi^{0}e^+\nu) < 5.4\times 10^{-8} ~ 90\%$ CL, 65 times lower than the one currently listed by PDG.