Study of Cabibbo suppressed decays of the Ds+ charmed-strange meson involving a KS0

We study the decay of Ds+ mesons into final states involving a KS0 and report the discovery of Cabibbo suppressed decay modes Ds+→KS0π−π+π+ (179±36 events) and Ds+→KS0π+ (113±26 events). The branching fraction ratios for the new modes are Γ(Ds+→KS0π−π+π+)Γ(Ds+→KS0K−π+π+)=0.18±0.04±0.05 and Γ(Ds+→KS0π+)Γ(Ds+→KS0K+)=0.104±0.024±0.014.