Measurement of the branching fraction of the doubly Cabibbo-suppressed decay $D^0\to K^+\pi^-\pi^0$ and search for $D^0\to K^+\pi^-\pi^0\pi^0$

TL;DR

This paper measures the branching fraction of a rare doubly Cabibbo-suppressed decay of the D0 meson and searches for a related decay mode, providing new experimental data and limits that test the Standard Model's flavor physics predictions.

Contribution

It provides the first measurement of the branching fraction for D0→K+π−π0 and sets an upper limit for D0→K+π−π0π0, enhancing understanding of charm quark decay dynamics.

Findings

Branching fraction of D0→K+π−π0 is approximately 3.13×10^{-4}.

No signal observed for D0→K+π−π0π0; upper limit set at 3.6×10^{-4}.

Ratios of DCS to CF decay branching fractions are consistent with theoretical expectations.

Abstract

Using $2.93\,\rm fb^{-1}$ of $e^+e^-$ collision data collected at a center-of-mass energy of 3.773\,GeV with the BESIII detector, we present a measurement of the branching fraction of the doubly Cabibbo-suppressed (DCS) decay $D^0\to K^+\pi^-\pi^0$ and a search for the DCS decay $D^0\to K^+\pi^-\pi^0\pi^0$. The branching fraction of $D^0\to K^+\pi^-\pi^0$ is determined to be $[3.13^{+0.60}_{-0.56}({\rm stat}) \pm 0.09({\rm syst})] \times 10^{-4}$. No signal is observed for $D^0\to K^+\pi^-\pi^0\pi^0$ and an upper limit of $3.6 \times 10^{-4}$ is set on the branching fraction at the 90\% C.L. We combine these results with the world-average branching fractions of their counterpart Cabibbo-favored decays to determine the ratios of the doubly Cabibbo-suppressed over the Cabibbo-favored branching fractions, ${\mathcal B}(D^0\to K^+\pi^-\pi^0)/{\mathcal B}(D^0\to K^-\pi^+\pi^0)=(0.22\pm 0.04)\%$~and ${\mathcal B}(D^0\to K^+\pi^-\pi^0\pi^0)/{\mathcal B}(D^0\to K^-\pi^+\pi^0\pi^0)<0.40\%$ at the 90\% C.L., which correspond to $(0.75\pm 0.14)\tan^{4} \theta_C$~and $1.37\times \tan^{4} \theta_C$, respectively, where $\theta_C$ is the Cabibbo angle.