U-spin symmetry in doubly Cabibbo-suppressed charmed meson decays

We prove a U-spin amplitude triangle relation among doubly Cabibbo-suppress ed (DCS) charmed meson decays, D-0 --> K(+)pi (-), D-0 --> K(0)pi (0) and D -s(+) --> (KK+)-K-0, congruent to an isospin relation among corresponding C abibbo-favored (CF) decays. U-spin breaking in relative phases between CF a nd DCS amplitudes affects time-dependent studies of D-0-(D) over bar (0) mi xing. Comparison of final state phase patterns in DCS and CF amplitude tria ngles, which can shed some light on these phases, is carried out in a pheno menological framework incorporating resonance contributions. (C) 2001 Publi shed by Elsevier Science B.V.