2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/206070Using data from the FOCUS (E831) experiment at Fermilab, we present a new measurement of the branching ratio for the Cabibbo-favored decay mode $D^0 \to K^-K^+π^-π^+$. From a sample of $2669 \pm 101$ fully reconstructed $D^0 \to K^-K^+π^-π^+$ events, we measure $Γ(D^0 \to K^-K^+π^-π^+)/Γ(D^0 \to K^-π^-π^+π^+) = 0.0295 \pm 0.0011(stat.) \pm 0.0008(syst.)$. A coherent amplitude analysis has been performed to determine the resonant substructure of this decay mode. This analysis reveals a dominant contribution from $D^0 \to K_1^+ K-$ modes.19 pages, 6 figures, to be submitted to Physics Letters BHigh Energy Physics - Experimenttext