Measurement of the Branching Ratio of $K_L \to e^+e^- \gamma\gamma$
T. Nakaya · 1995
This thesis presents new measurement of the $K_L \to e^+e^- \gamma\gamma$ branching ratio in Fermilab experiment E799. The decay $K_L \to e^+e^- \gamma\gamma$ is dominated by a $K_L$ Dalitz decay, $K_L \to e^+e^- \gamma$, with an internal bremsstrahlung photon. In addition, the decay $K_L \to e^+e^- \gamma\gamma$ has a small fraction from the direct emission process. This decay is important in order to understand the long distance physics, such as the $K_L \to \gamma\gamma^*$ form factor and the $K_L \to \gamma\gamma\gamma^*$ direct emission process. This decay mode also has been a focus on general attention as the most serious background to the CP violating decay $K_L \to \pi^0 e^+e^-$. We observed 58 $K_L \to e^+e^- \gamma\gamma$ events, and measured the branching ratio to be:...