Amplitude analysis and branching fraction measurement of the decay $D^0 \to K^+K^-π^0π^0$

Abstract

An amplitude analysis of the singly Cabibbo-suppressed decay $D^0 \to K^+ K^- π^0 π^0$ is performed, for the first time, to determine the relative magnitudes and phases of different intermediate processes. The analysis uses $e^+e^-$ collision data collected with the BESIII detector at the center-of-mass energy 3.773~GeV corresponding to an integrated luminosity of 20.3 $\rm fb^{-1}$. The absolute branching fraction of $D^0 \to K^+ K^- π^0 π^0$ is measured to be \BF. The dominant intermediate process is $D^0 \to K^{*}(892)^+K^{*}(892)^-$, with a branching fraction of $(2.79 \pm 0.13_{\rm{stat.}} \pm 0.11_{\rm{syst.}}) \times 10^{-3}$. Amplitude analysis reveals that the $D^0 \to K^{*}(892)^+K^{*}(892)^-$ decay is S-wave dominant. The longitudinal polarization fraction of $D^0 \to K^{*}(892)^+ K^{*}(892)^-$ is measured to be $0.468\pm0.046_{\rm{stat.}}\pm0.011_{\rm{syst.}}$.

Figures (4)

• Figure 1: Topological diagrams contributing to the decay $D^0 \rightarrow K^{*}(892)^+K^{*}(892)^-$ with (a) color-allowed external W-emission tree diagram and (b) color-suppressed internal $W$ emission and $W$-exchange diagram.
• Figure 2: Projections on (a) $M_{\rm BC}^{\rm tag}$ and (b) $M_{\rm BC}^{\rm sig}$ from the 2D fit. The points with error bars are data. The solid blue lines are the total fit result, the dotted red lines are the signal, and the dotted green lines are the background.
• Figure 3: Projections of the data sample and the fit result on the invariant mass distributions. The data are represented by points with error bars, the fit results by colored lines, and the background by blue histograms. The combinations of two identical $\pi^0$s are added due to the exchange symmetry.
• Figure 4: Fits to the $M_{\rm BC}$ distributions of the ST candidates for $\bar{D}^0 \to K^+ \pi^-$ (a), $\bar{D}^0 \to K^+ \pi^- \pi^0$ (b) and $\bar{D}^0 \to K^+ \pi^- \pi^- \pi^+$ (c). The points with error bars are data. The blue curves are the fit projections. The dotted red curves are the signal. The dotted green curves are the fitted combinatorial background shapes.