Measurement of branching fractions and search for $CP$ violation in $D^{0}\to\pi^{+}\pi^{-}\eta$, $D^{0}\to K^{+}K^{-}\eta$, and $D^{0}\to\phi\eta$ at Belle

• Main Authors: Schwartz, A. J, Aihara, H, Asner, D. M, Aulchenko, V, Behera, P, Bessner, M, Bilka, T, Biswal, J, Bonvicini, G, Bozek, A, Branchini, P, Browder, T. E, Budano, A, Campajola, M, Chang, M. -C, Chekelian, V, Chen, A, Chen, Y. Q, Chilikin, K, Cho, K, Cho, S. -J, Choi, S. -K, Choi, Y, Choudhury, S, Dash, N, De Pietro, G, Dhamija, R, Di Capua, F, Ferber, T, Garg, R, Gaur, V, Goldenzweig, P, Golob, B, Graziani, E, Hayasaka, K, Hou, W. -S, Inami, K, Iwasaki, Y, Jacobs, W. W, Jang, E. -J, Jia, S, Jin, Y, Kang, K. H, Karyan, G, Kim, C. H, Kim, D. Y, Kim, K. -H, Kim, Y. -K, Korobov, A, Kri\v, P, Krokovny, P, Kumar, M, Kumara, K, Kuzmin, A, Laurenza, M, Gioi, L. Li, Masuda, M, Miyabayashi, K, Mori, T, Nakao, M, Natkaniec, Z, Natochii, A, Nayak, M, Nisar, N. K, Nishimura, K, Pardi, S, Park, S. -H, Pestotnik, R, Piilonen, L. E, Popov, V, Prencipe, E, Rout, N, Sandilya, S, Sangal, A, Schwanda, C, Seino, Y, Senyo, K, Shapkin, M, Sharma, C, Shwartz, B, Sokolov, A, Stari\v, M, Takizawa, M, Tenchini, F, Uchida, M, Uglov, T, Uno, K, Uno, S, Vahsen, S. E, Van Tonder, R, Waheed, E, Wang, P, Watanuki, S, Won, E, Yabsley, B. D, Yan, W. B, Yang, S. B, Ye, H, Yusa, Y, Zhukova, V
• Format: Journal Article
• Language: English
• Published: 08.06.2021
• Subjects: Physics - High Energy Physics - Experiment
• DOI: 10.48550/arxiv.2106.04286

JHEP09(2021)075 We measure the branching fractions and $CP$ asymmetries for the singly Cabibbo-suppressed decays $D^{0}\to\pi^{+}\pi^{-}\eta$, $D^{0}\to K^{+}K^{-}\eta$, and $D^{0}\to\phi\eta$, using 980 fb$^{-1}$ of data from the Belle experiment at the KEKB $e^+e^-$ collider. We obtain \begin{eqnarray} \mathcal{B}(D^{0}\to\pi^{+}\pi^{-}\eta) & = & [1.22\pm 0.02\,({\rm stat})\pm 0.02\,({\rm syst})\pm 0.03\,(\mathcal{B}_{\rm ref})]\times 10^{-3}\,, \nonumber \\ \mathcal{B}(D^{0}\to K^{+}K^{-}\eta) & = & [1.80\,^{+0.07}_{-0.06}\,({\rm stat})\pm 0.04\,({\rm syst})\pm 0.05\,(\mathcal{B}_{\rm ref})]\times 10^{-4}\,, \nonumber \\ \mathcal{B}(D^{0}\to\phi\eta) & = & [1.84\pm 0.09\,({\rm stat})\pm 0.06\,({\rm syst})\pm 0.05\,(\mathcal{B}_{\rm ref})]\times 10^{-4}\,, \nonumber \end{eqnarray} where the third uncertainty ($\mathcal{B}_{\rm ref}$) is from the uncertainty in the branching fraction of the reference mode $D^{0}\to K^{-}\pi^{+}\eta$. The color-suppressed decay $D^{0}\to\phi\eta$ is observed for the first time, with very high significance. The results for the $CP$ asymmetries are \begin{eqnarray} A_{CP}(D^{0}\to\pi^{+}\pi^{-}\eta) & = & [0.9\pm 1.2\,({\rm stat})\pm 0.5\,({\rm syst})]\%\,, \nonumber \\ A_{CP}(D^{0}\to K^{+}K^{-}\eta) & = & [-1.4\pm 3.3\,({\rm stat})\pm 1.1\,({\rm syst})]\%\,, \nonumber \\ A_{CP}(D^{0}\to\phi\eta)&= & [-1.9\pm 4.4\,({\rm stat})\pm 0.6\,({\rm syst})]\%\,. \nonumber \end{eqnarray} The results for $D^{0}\to\pi^{+}\pi^{-}\eta$ are a significant improvement over previous results. The branching fraction and $A_{CP}$ results for $D^{0}\to K^{+}K^{-}\eta$, and the $A_{CP}$ result for $D^{0}\to\phi\eta$, are the first such measurements. No evidence for $CP$ violation is found in any of these decays.