New limit on the $K^0_L \to \pi^0 \nu \bar{\nu}$ decay rate

TL;DR

This paper reports a new experimental upper limit on the rare decay rate of $K^0_L o pi^0 u ar{ u}$, improving constraints on this process and contributing to understanding CP violation and new physics.

Contribution

First dedicated experiment by E391a sets a new upper limit on the decay's branching ratio, advancing the search for rare kaon decays.

Findings

Upper limit of $2.1 imes 10^{-7}$ at 90% confidence level

Used about 10% of collected data during initial data taking

Provides tighter constraints on the decay rate of $K^0_L o pi^0 u ar{ u}$

Abstract

The first dedicated experiment for the rare kaon decay $K^0_L \to \pi^0 \nu \bar{\nu}$ has been performed by the E391a collaboration at the KEK 12-GeV proton synchrotron. A new upper limit of $2.1 \times 10^{-7}$ at the 90% confidence level was set for the branching ratio of the decay $K^0_L \to \pi^0 \nu \bar{\nu}$ using about 10% of the data collected during the first period of data taking.