We report the results of a search for D0-D̄0 mixing in D0→K+π- decays based on 400fb-1 of data accumulated by the Belle detector at KEKB. Both assuming CP conservation and allowing for CP violation, we fit the decay-time distribution for the mixing parameters x′ and y′, as well as for the parameter RD, the ratio of doubly Cabibbo-suppressed decays to Cabibbo-favored decays. The 95% confidence level region in the (x′2,y′) plane is obtained using a frequentist method. Assuming CP conservation, we find x′2<0.72×10-3 and -9.9×10-3<y′<6.8×10-3 at the 95% confidence level; these are the most stringent constraints on the mixing parameters to date. The no-mixing point (0,0) has a confidence level of 3.9%. Assuming no mixing, we measure RD=(0.377±0.008±0.005)%.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)