# Experimental search for the decay long-lived neutral kaon going to muonium

#### Abstract

An experimental study of very rare decays of neutral kaons has been carried out at a new neutral beam line at the Alternating-Gradient Synchrotron at Brookhaven National Laboratory. One focus of this study was a search for the lepton-flavor violating decay $K\sbsp{L}{0}\to\mu e$. No candidate events indicating occurrence of this process were found. Measurement of the experimental sensitivity was performed by simultaneous observation of the decay $K\sbsp{L}{0}\to\pi\sp+\pi\sp-$. This yielded a limited at the 90% confidence level on the branching ratio $B(K\sbsp{L}{0}\to\mu e$) $<$ 2.2 $\times$ 10$\sp{-10}$. This limit represents a substantial improvement over previous limits on the rate for this process.

Particle physics

#### Recommended Citation

Urheim, Jon Erik, "Experimental search for the decay long-lived neutral kaon going to muonium" (1990). Dissertations available from ProQuest. AAI9026663.
https://repository.upenn.edu/dissertations/AAI9026663

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