Search for CP violation in the decays $D^+_{(s)} \to K_S^0\pi^+$ and $D^+_{(s)} \to K_S^0K^+$

TL;DR

This study searched for CP violation in specific charmed meson decays using a large dataset, finding no evidence but providing the most sensitive measurements to date for these decay channels.

Contribution

First measurement of CP asymmetries in $D^+_{(s)}$ decays to $K_S^0 ext{+} ext{pions or kaons}$ with unprecedented sensitivity.

Findings

No evidence of CP violation observed.

Most sensitive CP asymmetry measurements for these decays to date.

Measured asymmetries are consistent with zero within uncertainties.

Abstract

We have searched for CP violation in the charmed meson decays $D^{+}_{(s)}\to K^0_S\pi^+$ and $D^{+}_{(s)}\to K^0_S K^+$ using 673 fb$^{-1}$ of data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No evidence for CP violation is observed. We report the most sensitive CP asymmetry measurements to date for these decays: $A_{CP}^{D^+\to K^0_S\pi^+}=(-0.71\pm0.19\pm0.20)%$, $A_{CP}^{D^+_s\to K^0_S\pi^+}=(+5.45\pm2.50\pm0.33)%$, $A_{CP}^{D^+\to K^0_S K^+}=(-0.16\pm0.58\pm0.25)%$, and $A_{CP}^{D^+_s\to K^0_S K^+}=(+0.12\pm0.36\pm0.22)%$, where the first uncertainties are statistical and the second are systematic.