Study of D + and D + s Decay Properties at Belle

We report the first observation of the doubly Cabibbo-suppressed decay, D s → K Kπ and the significantly improved measurement of the doubly Cabibbo-suppressed decay, D → Kππ using 605 fb of data collected with the Belle detector at the KEKB asymmetric-energy ee collider. The branching ratio with respect to its Cabibbo-favored counterpart are B(D s → KKπ)/B(D s → K Kπ) = 0.229 ± 0.028 ± 0.012)% and B(D → Kππ)/B(D → Kππ) = (0.569± 0.018± 0.014)%, where the first uncertainties are statistical and the second is systematic. We also report the improved measurement of D → K SK + and D s → K 0 Sπ + branching ratios using the same amount of data samples. The measured branching ratios with respect to the Cabibbo-favored modes are B(D → K SK )/B(D → K Sπ ) = (0.1899 ± 0.0011 ± 0.0018) and B(D s → K 0 Sπ )/B(D s → K 0 SK ) = (0.0803 ± 0.0024 ± 0.0012).