Studies of the decays D^0 \rightarrow K_S^0K^-\pi^+ and D^0 \rightarrow K_S^0K^+\pi^-

TL;DR

This paper reports the first measurements of the coherence factor and strong-phase difference in D^0 decays to K_S^0Kπ, providing crucial inputs for improving the determination of the CKM angle gamma and understanding charm mixing.

Contribution

It presents the first experimental determination of the coherence factor and strong-phase difference in D^0 o K_S^0Kar{ ext{pi}} decays, using quantum-correlated data from ext{e}^+ ext{e}^- collisions.

Findings

Measured coherence factor R_{K_S^0Kar{ ext{pi}}} = 0.70 \, extpm \, 0.08

Measured strong-phase difference \, extdelta^{K_S^0Kar{ ext{pi}}} = (0.1 \, extpm \, 15.7)^ ext{o}

Determined the branching ratio B(D^0 o K_S^0K^+ ext{pi}^-)/B(D^0 o K_S^0K^- ext{pi}^+) = 0.592 \, extpm \, 0.044 ext{(stat)} \, extpm \, 0.018 ext{(syst)}.

Abstract

The first measurements of the coherence factor R_{K_S^0K\pi} and the average strong--phase difference \delta^{K_S^0K\pi} in D^0 \to K_S^0 K^\mp\pi^\pm decays are reported. These parameters can be used to improve the determination of the unitary triangle angle \gamma\ in B^- \rightarrow $\widetilde{D}K^-$ decays, where $\widetilde{D}$ is either a D^0 or a D^0-bar meson decaying to the same final state, and also in studies of charm mixing. The measurements of the coherence factor and strong-phase difference are made using quantum-correlated, fully-reconstructed D^0D^0-bar pairs produced in e^+e^- collisions at the \psi(3770) resonance. The measured values are R_{K_S^0K\pi} = 0.70 \pm 0.08 and \delta^{K_S^0K\pi} = (0.1 \pm 15.7)$^\circ$ for an unrestricted kinematic region and R_{K*K} = 0.94 \pm 0.12 and \delta^{K*K} = (-16.6 \pm 18.4)$^\circ$ for a region where the combined K_S^0 \pi^\pm invariant mass is within 100 MeV/c^2 of the K^{*}(892)^\pm mass. These results indicate a significant level of coherence in the decay. In addition, isobar models are presented for the two decays, which show the dominance of the K^*(892)^\pm resonance. The branching ratio {B}(D^0 \rightarrow K_S^0K^+\pi^-)/{B}(D^0 \rightarrow K_S^0K^-\pi^+) is determined to be 0.592 \pm 0.044 (stat.) \pm 0.018 (syst.), which is more precise than previous measurements.