First search for $K_{L}\to\pi^{0}\pi^{0}\nu\bar{\nu}$

TL;DR

This paper reports the first experimental search for the rare decay of a neutral kaon into two neutral pions and a neutrino-antineutrino pair, setting upper limits on its branching ratio.

Contribution

It presents the first search results and upper limits for the decay mode $ ext{K}_L o ext{pi}^0 ext{pi}^0 u ar{ u}$ and related decay modes, using data from the E391a experiment.

Findings

Upper limit of $4.7 imes 10^{-5}$ on the branching ratio for $ ext{K}_L o ext{pi}^0 ext{pi}^0 u ar{ u}$

First experimental limits for the decay mode $ ext{K}_L o ext{pi}^0 ext{pi}^0 P$ with a pseudoscalar particle P

Constraints on rare kaon decay modes from initial data analysis

Abstract

The first search for the rare kaon decay $\kppnn$ has been performed by the E391a collaboration at the KEK 12-GeV proton synchrotron. An upper limit of $4.7\times10^{-5}$ at the 90 % confidence level was set for the branching ratio of the decay $\kppnn$ using about 10 % of the data collected during the first period of data taking. First limits for the decay mode $\kppP$, where $P$ is a pseudoscalar particle, were also set.