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Measurement of branching fractions and search for CP violation in D0π+πη, D0K+Kη, and D0ϕη at Belle

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We measure the branching fractions and CP asymmetries for the singly Cabibbo-suppressed decays D0π+πη, D0K+Kη, and D0ϕη, using 980 fb1 of data from the Belle experiment at the KEKB e+e collider. We obtain

$$ {\displaystyle \begin{array}{c}\mathcal{B}\left({D}^0\to {\pi}^{+}{\pi}^{-}\eta \right)=\left[1.22\pm 0.02\left(\mathrm{stat}\right)\pm 0.02\left(\mathrm{syst}\right)\pm 0.03\left({\mathcal{B}}_{\mathrm{ref}}\right)\right]\times {10}^{-3},\\ {}\mathcal{B}\left({D}^0\to {K}^{+}{K}^{-}\eta \right)=\left[{1.80}_{-0.06}^{+0.07}\left(\mathrm{stat}\right)\pm 0.04\left(\mathrm{syst}\right)\pm 0.05\left({\mathcal{B}}_{\mathrm{ref}}\right)\right]\times {10}^{-4},\\ {}\mathcal{B}\left({D}^0\to \phi \eta \right)=\left[1.84\pm 0.09\left(\mathrm{stat}\right)\pm 0.06\left(\mathrm{syst}\right)\pm 0.05\left({\mathcal{B}}_{\mathrm{ref}}\right)\right]\times {10}^{-4},\end{array}} $$

where the third uncertainty (\( \mathcal{B} \)ref) is from the uncertainty in the branching fraction of the reference mode D0Kπ+η. The color-suppressed decay D0ϕη is observed for the first time, with very high significance. The results for the CP asymmetries are

$$ {\displaystyle \begin{array}{c}{A}_{CP}\left({D}^0\ {\pi}^{+}{\pi}^{-}\eta \right)=\left[0.9\pm 1.2\left(\mathrm{stat}\right)\pm 0.5\left(\mathrm{syst}\right)\right]\%,\\ {}{A}_{CP}\left({D}^0\to {K}^{+}{K}^{-}\eta \right)=\left[-1.4\pm 3.3\left(\mathrm{stat}\right)\pm 1.1\left(\mathrm{syst}\right)\right]\%,\\ {} ACP\ \left({D}^0\to \phi \eta \right)=\left[-1.9\pm 4.4\left(\mathrm{stat}\right)\pm 0.6\left(\mathrm{syst}\right)\right]\%.\end{array}} $$

The results for D0π+πη are a significant improvement over previous results. The branching fraction and ACP results for D0K+Kη, and the ACP result for D0ϕη, are the first such measurements. No evidence for CP violation is found in any of these decays.


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The Belle collaboration., Li, L.K., Schwartz, A.J. et al. Measurement of branching fractions and search for CP violation in D0π+πη, D0K+Kη, and D0ϕη at Belle. J. High Energ. Phys. 2021, 75 (2021).

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  • Branching fraction
  • Charm physics
  • CP violation
  • e +-e Experiments