PNNL

We report a study of the decay D0 ? K0SK0S using 921 fb-1 of data collected at or near the ?ð4SÞ and ?ð5SÞ resonances with the Belle detector at the KEKB asymmetric energy eþe- collider. The measured time-integrated CP asymmetry is ACPðD0 ? K0 SK0S Þ ¼ ð-0.02 1.53 0.02 0.17Þ%, and the branching fraction is BðD0 ? K0 SK0S Þ ¼ ð1.321 0.023 0.036 0.044Þ × 10-4, where the first uncertainty is statistical, the second is systematic, and the third is due to the normalization mode (D0 ? K0Sp0). These results are significantly more precise than previous measurements available for this mode. The ACP measurement is consistent with the standard model expectation.