Measurement of branching fractions and search for CP violation in D 0 → π + π − η, D 0 → K + K − η, and D 0 → ϕη at Belle

We measure the branching fractions and CP asymmetries for the singly Cabibbo-suppressed decays D0 → π+π−η, D0 → K+K−η, and D0 → ϕη, using 980 fb−1 of data from the Belle experiment at the KEKB e+e− collider. We obtainB(D0→π+π−η)=[1.22±0.02(stat)±0.02(syst)±0.03(Bref)]×10−3,B(D0→K+K−η)=[1.80−0.06+0.07(stat)±0.04(syst)±0.05(Bref)]×10−4,B(D0→ϕη)=[1.84±0.09(stat)±0.06(syst)±0.05(Bref)]×10−4, where the third uncertainty (Bref) is from the uncertainty in the branching fraction of the reference mode D0 → K−π+η. The color-suppressed decay D0 → ϕη is observed for the first time, with very high significance. The results for the CP asymmetries areACP(D0π+π−η)=[0.9±1.2(stat)±0.5(syst)]%,ACP(D0→K+K−η)=[−1.4±3.3(stat)±1.1(syst)]%,ACP(D0→ϕη)=[−1.9±4.4(stat)±0.6(syst)]%. The results for D0 → π+π−η are a significant improvement over previous results. The branching fraction and ACP results for D0 → K+K−η, and the ACP result for D0 → ϕη, are the first such measurements. No evidence for CP violation is found in any of these decays. [Figure not available: see fulltext.]