Observation of the decay mode K_L -> pi^+ pi^- e^+ e^-

TL;DR

This paper reports the experimental observation of the rare decay mode K_L -> pi^+ pi^- e^+ e^-, measuring its branching ratio and confirming consistency with theoretical predictions.

Contribution

First experimental measurement of the K_L -> pi^+ pi^- e^+ e^- decay branching ratio, validating theoretical models.

Findings

Branching ratio measured as (4.4 +- 1.3(stat) +- 0.5(syst)) x 10^{-7}

Observed 13.5 +- 4.0 events

Results agree with theoretical predictions

Abstract

We report on results of an experimental search for the K_L -> pi^+ pi^- e^+ e^- decay mode. We found 13.5 +- 4.0 events and determined its branching ratio to be (4.4 +- 1.3(stat) +- 0.5(syst))*10^{-7}. The result agrees well with the theoretical prediction.