U-Spin Symmetry in Doubly Cabibbo-Suppressed Charmed Meson Decays

We propose tests of U-spin symmetry in doubly Cabibbo-suppressed (DCS) charmed meson decays, $D^{0,+}\to K\pi, D^+_s\to KK$, in decays to pairs of a vector and a pseudoscalar meson, and in decays to pairs of two vector mesons. U-spin breaking in relative phases between Cabibbo-favored (CF) and DCS amplitudes affects time-dependent studies of $D^0-\od$ mixing. Comparison of final state phase patterns in DCS and CF amplitude triangles, which can shed some light on these phases, is carried out in a phenomenological framework incorporating resonance contributions.