Search for $CP$ Violation in the Decays $D_{(s)}^{+}\to K_S^0{\pi }^{+}$ and $D_{(s)}^{+}\to K_S^0{K}^{+}$

We have searched for $CP$ violation in the charmed meson decays $D_{(s)}^{+}\to K_S^0{\pi }^{+}$ and $D_{(s)}^{+}\to K_S^0{K}^{+}$ using $673{\mathrm{fb}}^{-1}$ 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: $A_{CP}^{D^{+}\to K_S^0{\pi }^{+}}=(-0.71\pm 0.19\pm 0.20)\%$, $A_{CP}^{D_s^{+}\to K_S^0{\pi }^{+}}=(+5.45\pm 2.50\pm 0.33)\%$, $A_{CP}^{D^{+}\to K_S^0{K}^{+}}=(-0.16\pm 0.58\pm 0.25)\%$, and $A_{CP}^{D_s^{+}\to K_S^0{K}^{+}}=(+0.12\pm 0.36\pm 0.22)\%$, where the first uncertainties are statistical and the second are systematic.