First Observation of A? plus and A?- Signals near the ?KN(I=1) Mass Threshold in Ac plus ? A? plus ? plus ?- Decay
Y. Ma,J. Yelton,K. Tanida,I. Adachi,J. K. Ahn,H. Aihara,S. Al Said,D. M. Asner,H. Atmacan,T. Aushev,R. Ayad,V. Babu,S. Bahinipati,Sw. Banerjee,P. Behera,K. Belous,J. Bennett,M. Bessner,B. Bhuyan,T. Bilka,D. Biswas,A. Bobrov,D. Bodrov,J. Borah,A. Bozek,M. Bracko,P. Branchini,T. E. Browder,A. Budano,M. Campajola,D. Cervenkov,M-C Chang,A. Chen,B. G. Cheon,K. Chilikin,H. E. Cho,K. Cho,S-J Cho,S-K Choi,Y. Choi,S. Choudhury,D. Cinabro,S. Das,G. De Nardo,G. De Pietro,R. Dhamija,F. Di Capua,J. Dingfelder,Z. Dolezal,T. Dong,D. Epifanov,T. Ferber,D. Ferlewicz,B. G. Fulsom,R. Garg,V. Gaur,A. Garmash,A. Giri,P. Goldenzweig,B. Golob,E. Graziani,K. Gudkova,C. Hadjivasiliou,S. Halder,K. Hayasaka,H. Hayashii,M. T. Hedges,W-S Hou,C-L Hsu,K. Inami,N. Ipsita,A. Ishikawa,R. Itoh,M. Iwasaki,W. W. Jacobs,E-J Jang,S. Jia,Y. Jin,A. B. Kaliyar,K. H. Kang,T. Kawasaki,C. Kiesling,C. H. Kim,D. Y. Kim,Y-K Kim,K. Kinoshita,P. Kodys,A. Korobov,S. Korpar,E. Kovalenko,P. Krizan,P. Krokovny,R. Kumar,K. Kumara,Y-J Kwon,T. Lam,J. S. Lange,S. C. Lee,P. Lewis,L. K. Li,Y. Li,L. Li Gioi,J. Libby,K. Lieret,Y. -r. Lin,D. Liventsev,T. Luo,M. Masuda,T. Matsuda,D. Matvienko,S. K. Maurya,F. Meier,M. Merola,F. Metzner,K. Miyabayashi,G. B. Mohanty,R. Mussa,I. Nakamura,T. Nakano,M. Nakao,Z. Natkaniec,A. Natochii,L. Nayak,M. Nayak,N. K. Nisar,S. Nishida,S. Ogawa,H. Ono,P. Oskin,P. Pakhlov,G. Pakhlova,S. Pardi,H. Park,J. Park,S. Patra,S. Paul,R. Pestotnik,L. E. Piilonen,T. Podobnik,E. Prencipe,M. T. Prim,A. Rostomyan,N. Rout,G. Russo,S. Sandilya,L. Santelj,V. Savinov,G. Schnell,J. Schueler,C. Schwanda,Y. Seino,K. Senyo,M. E. Sevior,W. Shan,M. Shapkin,C. Sharma,C. P. Shen,J-G Shiu,F. Simon,A. Sokolov,E. Solovieva,M. Staric,M. Sumihama,T. Sumiyoshi,W. Sutcliffe,M. Takizawa,U. Tamponi,F. Tenchini,M. Uchida,S. Uehara,T. Uglov,Y. Unno,K. Uno,S. Uno,P. Urquijo,Y. Usov,S. E. Vahsen,R. van Tonder,G. Varner,A. Vinokurova,A. Vossen,D. Wang,M-Z Wang,M. Watanabe,S. Watanuki,O. Werbycka,E. Won,X. Xu,B. D. Yabsley,W. Yan,S. B. Yang,J. H. Yin,C. Z. Yuan,L. Yuan,Z. P. Zhang,V. Zhilich,V. Zhukova
PHYSICAL REVIEW LETTERS（2023）
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摘要
Using the data sample of 980 fb-1 collected with the Belle detector operating at the KEKB asymmetric -energy e+e- collider, we present the results of an investigation of the Az+ and Az- invariant mass distributions looking for substructure in the decay A+c -> Az+z+z-. We find a significant signal in each mass distribution. When interpreted as resonances, we find for the Az+ (Az-) combination a mass of 1434.3 +/- 0.6(stat) +/- 0.9(syst) MeV=c2 [1438.5 +/- 0.9(stat) +/- 2.5(syst) MeV=c2], an intrinsic width of 11.5 +/- 2.8(stat) +/- 5.3(syst) MeV=c2 [33.0 +/- 7.5(stat) +/- 23.6(syst) MeV=c2] with a significance of 7.5u (6.2u). As these two signals are very close to the over bar KN threshold, we also investigate the possibility of a over bar KN cusp, and find that we cannot discriminate between these two interpretations due to the limited size of the data sample.
