Measurement of branching fractions of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">Λ</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup><mml:mo stretchy="false">→</mml:mo><mml:mi>η</mml:mi><mml:mi mathvariant="normal">Λ</mml:mi><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>η</mml:mi><mml:msup><mml:mrow><mml:mi mathvariant="normal">Σ</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Λ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>1670</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>η</mml:mi><mml:mi mathvariant="normal">Σ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>1385</mml:mn><mml:msup><mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>
J. Y. Lee, K. Tanida, Yuji Katō, S. K. Kim, S. B. Yang, I. Adachi, J. K. Ahn, H. Aihara, S. Al Said, D. M. Asner, T. Aushev, R. Ayad, V. Babu, S. Bahinipati, P. K. Behera, C. Beleño, J. V. Bennett, M. Bessner, B. Bhuyan, T. Bilka, J. P. Biswal, G. Bonvicini, A. Bożek, M. Bračko, T. E. Browder, M. Campajola, L. Cao, D. Červenkov, M.-C. Chang, P. Chang, V. Chekelian, A. Chen, B. G. Cheon, K. Chilikin, K. Cho, S. K. Choi, Y. Choi, S. Choudhury, D. Cinabro, S. Cunliffe, G. De Nardo, F. Di Capua, Z. Doležal, T. V. Dong, S. Eidelman, D. Epifanov, T. Ferber, B. G. Fulsom, R. B. Garg, V. Gaur, A. Garmash, A. Giri, P. Goldenzweig, B. Golob, C. Hadjivasiliou, O. Hartbrich, K. Hayasaka, H. Hayashii, M. T. Hedges, M. Hernández Villanueva, C.-L. Hsu, K. Inami, A. Ishikawa, R. Itoh, M. Iwasaki, W. W. Jacobs, E.-J. Jang, S. Jia, Y. Jin, C. Joo, K. K. Joo, K. Kang, G. Karyan, H. Kichimi, C. Kiesling, B. H. Kim, D. Y. Kim, Kyoungmin Kim, K. T. Kim, S. H. Kim, Y. J. Kim, Y. K. Kim, K. Kinoshita, P. Kodyš, S. Korpar, D. Kotchetkov, P. Križan, R. Kroeger, P. Krokovny, T. Kuhr, R. Kulasiri, K. Kumara, A. Kuzmin, Y.-J. Kwon, S. C. Lee, C. H. Li, L. K. Li, Y. B. Li, L. Li Gioi, J. Libby
Abstract
We report branching fraction measurements of four decay modes of the ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}$ baryon, each of which includes an $\ensuremath{\eta}$ meson and a $\mathrm{\ensuremath{\Lambda}}$ baryon in the final state, and all of which are measured relative to the ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ decay mode. The results are based on a $980\text{ }\text{ }\mathrm{f}{\mathrm{b}}^{\ensuremath{-}1}$ data sample collected by the Belle detector at the KEKB asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider. Two decays, ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\ensuremath{\eta}{\mathrm{\ensuremath{\Sigma}}}^{0}{\ensuremath{\pi}}^{+}$ and $\mathrm{\ensuremath{\Lambda}}(1670){\ensuremath{\pi}}^{+}$, are observed for the first time, while the measurements of the other decay modes, ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\ensuremath{\eta}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\pi}}^{+}$ and $\ensuremath{\eta}\mathrm{\ensuremath{\Sigma}}(1385{)}^{+}$, are more precise than those made previously. We obtain relative branching fractions of $\mathcal{B}({\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\ensuremath{\eta}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\pi}}^{+})/\phantom{\rule{0ex}{0ex}}\mathcal{B}({\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})=0.293\ifmmode\pm\else\textpm\fi{}0.003\ifmmode\pm\else\textpm\fi{}0.014$, $\mathcal{B}({\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\ensuremath{\eta}{\mathrm{\ensuremath{\Sigma}}}^{0}{\ensuremath{\pi}}^{+})/\mathcal{B}({\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})=0.120\ifmmode\pm\else\textpm\fi{}0.006\ifmmode\pm\else\textpm\fi{}0.010$, $\mathcal{B}({\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}(1670){\ensuremath{\pi}}^{+})\ifmmode\times\else\texttimes\fi{}\mathcal{B}(\mathrm{\ensuremath{\Lambda}}(1670)\ensuremath{\rightarrow}\ensuremath{\eta}\mathrm{\ensuremath{\Lambda}})/\mathcal{B}({\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})=(5.54\ifmmode\pm\else\textpm\fi{}0.29\ifmmode\pm\else\textpm\fi{}0.73)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$, and $\mathcal{B}({\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\ensuremath{\eta}\mathrm{\ensuremath{\Sigma}}(1385{)}^{+})/\mathcal{B}({\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})=0.192\ifmmode\pm\else\textpm\fi{}0.006\ifmmode\pm\else\textpm\fi{}0.016$. The mass and width of the $\mathrm{\ensuremath{\Lambda}}(1670)$ are also precisely determined to be $1674.3\ifmmode\pm\else\textpm\fi{}0.8\ifmmode\pm\else\textpm\fi{}4.9\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $36.1\ifmmode\pm\else\textpm\fi{}2.4\ifmmode\pm\else\textpm\fi{}4.8\text{ }\text{ }\mathrm{MeV}$, respectively, where the uncertainties are statistical and systematic, respectively.