Search for $C\!P$ violation and measurement of branching fractions and
decay asymmetry parameters for $\Lambda_c^+\to\Lambda h^+$ and
$\Lambda_c^+\to\Sigma^{0} h^+$ ($h\!=\!K,\,\pi$)
Belle Collaboration,L. K. Li,W. Shan,K. Kinoshita,I. Adachi,H. Aihara,D. M. Asner,H. Atmacan,T. Aushev,V. Babu,S. Bahinipati,Sw. Banerjee,P. Behera,J. Bennett,M. Bessner,V. Bhardwaj,B. Bhuyan,T. Bilka,A. Bobrov,D. Bodrov,J. Borah,M. Bračko,P. Branchini,A. Budano,M. Campajola,D. Červenkov,M. -C. Chang,P. Chang,V. Chekelian,A. Chen,B. G. Cheon,K. Chilikin,H. E. Cho,K. Cho,S. -J. Cho,S. -K. Choi,Y. Choi,S. Choudhury,D. Cinabro,N. Dash,G. De Nardo,G. De Pietro,R. Dhamija,F. Di Capua,Z. Doležal,T. V. Dong,D. Epifanov,T. Ferber,A. Frey,B. G. Fulsom,V. Gaur,A. Garmash,A. Giri,P. Goldenzweig,G. Gong,E. Graziani,T. Gu,Y. Guan,K. Gudkova,C. Hadjivasiliou,K. Hayasaka,H. Hayashii,M. T. Hedges,W. -S. Hou,C. -L. Hsu,K. Inami,A. Ishikawa,R. Itoh,W. W. Jacobs,E. -J. Jang,Q. P. Ji,S. Jia,Y. Jin,K. K. Joo,C. Kiesling,C. H. Kim,D. Y. Kim,K. -H. Kim,P. Kodyš,T. Konno,A. Korobov,S. Korpar,E. Kovalenko,P. Krokovny,T. Kuhr,R. Kumar,K. Kumara,A. Kuzmin,Y. -J. Kwon,Y. -T. Lai,T. Lam,J. S. Lange,S. C. Lee,J. Li,S. X. Li,Y. Li,Y. B. Li,L. Li Gioi,J. Libby,K. Lieret,M. Masuda,S. K. Maurya,M. Merola,F. Metzner,K. Miyabayashi,R. Mizuk,R. Mussa,M. Nakao,Z. Natkaniec,A. Natochii,L. Nayak,M. Nayak,M. Niiyama,N. K. Nisar,S. Nishida,S. Ogawa,H. Ono,P. Oskin,G. Pakhlova,S. Pardi,H. Park,S. -H. Park,A. Passeri,S. Patra,S. Paul,T. K. Pedlar,R. Pestotnik,L. E. Piilonen,T. Podobnik,E. Prencipe,M. T. Prim,A. Rostomyan,N. Rout,G. Russo,D. Sahoo,Y. Sakai,S. Sandilya,A. Sangal,V. Savinov,G. Schnell,J. Schueler,C. Schwanda,A. J. Schwartz,Y. Seino,K. Senyo,M. E. Sevior,M. Shapkin,C. Sharma,C. P. Shen,J. -G. Shiu,J. B. Singh,A. Sokolov,E. Solovieva,M. Starič,M. Sumihama,K. Sumisawa,T. Sumiyoshi,W. Sutcliffe,M. Takizawa,U. Tamponi,K. Tanida,F. Tenchini,M. Uchida,T. Uglov,Y. Unno,S. Uno,Y. Usov,S. E. Vahsen,R. van Tonder,G. Varner,A. Vinokurova,A. Vossen,E. Waheed,E. Wang,X. L. Wang,M. Watanabe,S. Watanuki,O. Werbycka,E. Won,X. Xu,B. D. Yabsley,W. Yan,S. B. Yang,J. Yelton,J. H. Yin,Y. Yook,C. Z. Yuan,Z. P. Zhang,V. Zhilich,V. Zhukova
arxiv（2023）
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摘要
We report a study of $\Lambda_c^+\to\Lambda h^+$ and $\Lambda_c^+\to\Sigma^{0} h^+$ ($h\!=\!K,\,\pi$) decays based on a data sample of 980~${\rm fb}^{-1}$ collected with the Belle detector at the KEKB energy-asymmetric $e^+e^-$ collider. The first results of direct $C\!P$ asymmetry in two-body singly Cabibbo-suppressed (SCS) decays of charmed baryons are measured, $A_{C\!P}^{\rm{dir}}(\Lambda_c^+\to\Lambda K^+)\!=\!+0.021\pm0.026\pm0.001$ and $A_{C\!P}^{\rm{dir}}(\Lambda_c^+\to\Sigma^0K^+)\!=\!+0.025\pm0.054\pm0.004$. We also make the most precise measurement of the decay asymmetry parameters ($\alpha$) for the four modes of interest and search for $C\!P$ violation via the $\alpha$-induced $C\!P$ asymmetry ($A_{C\!P}^{\alpha}$). We measure $A_{C\!P}^{\alpha}(\Lambda_c^+\to\Lambda K^+)\!=\!{-0.023\pm0.086\pm0.071}$ and $A_{C\!P}^{\alpha}(\Lambda_c^+\to\Sigma^0K^+)\!=\!{+0.08\pm 0.35\pm 0.14}$, which are the first $A_{C\!P}^{\alpha}$ results for SCS decays of charmed baryons. We search for $\Lambda$-hyperon $C\!P$ violation in $\Lambda_c^+\to(\Lambda,\,\Sigma^0)\pi^+$ and find $A_{C\!P}^{\alpha}(\Lambda\to p\pi^{-})\!=\!{+0.013\pm0.007\pm0.011}$. This is the first time that hyperon $C\!P$ violation has been measured via Cabibbo-favored charm decays. No evidence of baryon $C\!P$ violation is found. We also obtain the most precise branching fractions for two SCS $\Lambda_c^+$ decays, $\mathcal{B}(\Lambda_c^+\to\Lambda K^+)\!=\!(6.57\pm0.17\pm0.11\pm0.35)\times10^{-4}$ and $\mathcal{B}(\Lambda_c^+\to\Sigma^0K^+)\!=\!(3.58\pm0.19\pm0.06\pm0.19)\times10^{-4}$. The first uncertainties are statistical and the second systematic, while the third uncertainties come from the uncertainties on the world average branching fractions of $\Lambda_c^+\to(\Lambda,\,\Sigma^0)\pi^+$.
