Measurement of the strong-phase difference between $D^0$ and $\bar{D^0}\to K^+K^-\pi^+\pi^-$ in bins of phase space

Abstract

A first determination of the strong-phase difference between $D^0$ and $\bar{D^0}\to K^+K^-\pi^+\pi^-$ is performed using $e^+e^-\to\psi(3770)\to D\bar{D}$ data collected by the BESIII detector corresponding to an integrated luminosity of $20.3$ fb$^{-1}$. The measurements are made in four pairs of bins in phase space, which are chosen to provide optimal sensitivity to the angle $\gamma$ of the Unitarity Triangle in $B^\pm \to DK^\pm$ decays. From these measurements, it follows that the $C\!P$-even fraction of the decay is $F_+ = 0.754 \pm 0.010_{\rm \, stat.} \pm 0.008_{\rm \, syst.}$. In addition, the branching fraction of $D^0 \to K^+K^-\pi^+\pi^-$ is measured to be $(2.863 \pm 0.028_{\rm \, stat.} \pm 0.045_{\rm \, syst.})\times10^{-3}$, which is twice as precise as previous results obtained at other experiments.