# ICHEP2018 SEOUL

Jul 4 – 11, 2018
COEX, SEOUL
Asia/Seoul timezone

## Status of $K_L^0 \rightarrow \pi^0 \gamma \gamma$ in the KOTO Experiment at J-PARC

Jul 6, 2018, 6:30 PM
2h
COEX, SEOUL

Poster

### Speaker

Mr Chieh Lin (National Taiwan University)

### 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.

### Primary author

Mr Chieh Lin (National Taiwan University)

### Co-author

Yee Hsiung (National Taiwan University (TW))

### Presentation materials

There are no materials yet.