Search for the Decay $K_L \to \pi^0 \mu^+ \mu^-$

TL;DR

This paper reports a search for the rare decay $K_L o \pi^0 \mu^+ \mu^-$, aiming to investigate CP violation and potential new physics, setting an upper limit on its branching ratio based on Fermilab data.

Contribution

First experimental search for $K_L o \pi^0 \\mu^+ \\mu^-$ decay, providing constraints on CP violation and new physics beyond the Standard Model.

Findings

Observed 2 events with expected background of 0.87 ± 0.15

Set an upper limit on the branching ratio: < 3.8 x 10^{-10} at 90% CL

Results support ongoing investigations into CP violation mechanisms.

Abstract

We report on a search for the decay \klpimumu carried out as a part of the KTeV experiment at Fermilab. This decay is expected to have a significant $CP$ violating contribution and a direct measurement will either support the CKM mechanism for CP violation or point to new physics. Two events were observed in the 1997 data with an expected background of $0.87 \pm 0.15$ events, and we set an upper limit \BR{\klpimumu} $ <3.8 \times 10^{-10}$ at the 90% confidence level.