By analyzing $e^+e^-$ annihilation data corresponding to an integrated luminosity of $2.93\,\rm fb^{ -1}$ collected at the center-of-mass energy of 3.773\,GeV with the BESIII detector, we report the first observations of the doubly Cabibbo-suppressed decays $D^+\to K^+\pi^0\pi^0$ and $D^+\to K^+\pi^0\eta$. The branching fractions of $D^+\to K^+\pi^0\pi^0$ and $D^+\to K^+\pi^0\eta$ are measured to be $(2.1 \pm 0.4_{ \rm stat} \pm 0.1_{ \rm syst})\times 10^{ -4}$ and $(2.1 \pm 0.5_{ \rm stat} \pm 0.1_{ \rm syst})\times 10^{ -4}$ with statistical significances of 8.8$\sigma$ and 5.5$\sigma$, respectively. In addition, we search for the subprocesses $D^+\to K^{ *}(892)^{ +}\pi^0$ and $D^+\to K^{ *}(892)^{ +}\eta$ with $K^{ *}(892)^+\to K^+\pi^0$. The branching fraction of $D^+\to K^{ *}(892)^{ +}\eta$ is determined to be $({ 4.4^{ +1.8}_{ -1.5}}_{ \rm stat}\pm0.2_{ \rm syst})\times10^{ -4}$, with a statistical significance of 3.2$\sigma$. No significant signal for $D^+\to K^{ *}(892)^{ +}\pi^0$ is found and we set an upper limit on the branching fraction of this decay at the 90\% confidence level to be $5.4\times10^{ -4}$.
Categories: hep-ex