Search for $CP$ violation in $D$ decays to radiative and hadronic decays and search for rare $D$ decay at Belle

TL;DR

This paper reports on measurements of $D$ meson decays to radiative and hadronic final states, including the first observation of $D^0 ightarrow ho^0\gamma$, $CP$ asymmetry measurements, and a new upper limit on the rare decay $D^0 ightarrow \gamma\gamma$ using Belle data.

Contribution

It presents the first observation of $D^0 ightarrow ho^0\gamma$, new $CP$ asymmetry measurements, and the most restrictive upper limit on $D^0 ightarrow \gamma\gamma$ decay.

Findings

First observation of $D^0 ightarrow ho^0\gamma$ decay.

$CP$ asymmetry in $D^0 ightarrow K^0_S K^0_S$ consistent with no violation.

Most restrictive upper limit on $D^0 ightarrow \gamma\gamma$ decay.

Abstract

Using the large data sample accumulated by the Belle experiment at KEKB asymmetry energy $e^+e^-$ Collider, we report the preliminary measurements of the branching fractions of the radiative decays $D^0 \rightarrow V\gamma$, where $V$ = $\phi,\bar{K^*}^0, \rho^0$. This is the first observation of the decay $D^0 \rightarrow \rho^0\gamma$ and also present the preliminary results of the first measurement of $CP$ asymmetry in these decays. We present the preliminary result of the $CP$ asymmetry of the $D^0 \rightarrow K^0_S K^0_S$ decay, which is consistent with no $CP$ violation and improves the uncertainty with respect to the previous measurement of this quantity by more than a factor of three. Finally, we present the results of the rare charm decay $D^0 \rightarrow \gamma\gamma$, resulting in the most restrictive upper limit to date.