Measurement of branching fractions and search for CP violation in D0→π+π−η, D0→K+K−η, and D0→ϕη at Belle

Journal of High Energy Physics. 2021.

Aushev T., Pakhlova G., Uglov T., Mizuk R., Попов В. Е.

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 obtain

(𝐷0→𝜋+𝜋−𝜂)=[1.22±0.02(stat)±0.02(syst)±0.03(ref)]×10−3,(𝐷0→𝐾+𝐾−𝜂)=[1.80+0.07−0.06(stat)±0.04(syst)±0.05(ref)]×10−4,(𝐷0→𝜙𝜂)=[1.84±0.09(stat)±0.06(syst)±0.05(ref)]×10−4,B(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 are

𝐴𝐶𝑃(𝐷0 𝜋+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)]%.ACP(D0 π+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.

Keywords: CP violation, Branching fraction, Charm physics

Publication based on the results of: Investigation of the nature of the bottomonium states on the data of the Belle experiment and development of new research methods in charm and tau-lepton physics in experiments on electron-positron colliders (2021)