Speaker
Description
$K_L^0 \rightarrow \pi^0 \gamma \gamma$ has been predicted by $\mathscr{O}(6)$ calculation in chiral perturbation theory (ChPT) with the inclusion of the vector meson exchange terms. An effective coupling constant $\alpha_V$ was introduced to incorporate with the vector meson contributions. This decay mode is also crucial for the determination of the direct CP violation amplitude of $K_L^0 \rightarrow \pi^0 l^+ l^-$. Fermilab E832 and CERN NA48 had measured the branching ratio and pole parameter $\alpha_V$ around $1.3 \times 10^{-6}$ and $-0.4$ respectively.
In 2017, a trigger based on the number of EM-shower clusters by Clock Distribution and Trigger (CDT) module was commissioned to collect $K_L^0 \rightarrow \pi^0 \gamma \gamma$ events more effectively. The analysis status based on 2017 run data will be presented.
