Measurement of e + e − → π + π − ψ ( 2 S ) via initial state radiation at Belle

• Published in: Physical review. D, Particles, fields, gravitation, and cosmology Particles, fields, gravitation, and cosmology, 2015-06, Vol.91 (11), Article 112007
• Main Authors: Wang, X. L., Yuan, C. Z., Shen, C. P., Wang, P., Abdesselam, A., Adachi, I., Aihara, H., Al Said, S., Arinstein, K., Asner, D. M., Ayad, R., Bakich, A. M., Bansal, V., Bhuyan, B., Bobrov, A., Bonvicini, G., Bračko, M., Browder, T. E., Červenkov, D., Chang, P., Chekelian, V., Chen, A., Cheon, B. G., Chilikin, K., Chistov, R., Cho, K., Chobanova, V., Choi, S.-K., Choi, Y., Cinabro, D., Dalseno, J., Danilov, M., Doležal, Z., Drásal, Z., Drutskoy, A., Dutta, K., Eidelman, S., Farhat, H., Fast, J. E., Ferber, T., Gaur, V., Garmash, A., Getzkow, D., Gillard, R., Goh, Y. M., Haba, J., Hayasaka, K., Hayashii, H., He, X. H., Hou, W.-S., Iijima, T., Inami, K., Ishikawa, A., Itoh, R., Iwasaki, Y., Joffe, D., Julius, T., Kang, K. H., Kato, E., Kawasaki, T., Kiesling, C., Kim, D. Y., Kim, H. J., Kim, J. B., Kim, J. H., Kim, M. J., Kim, S. H., Kim, Y. J., Kinoshita, K., Ko, B. R., Kodyš, P., Korpar, S., Križan, P., Krokovny, P., Kuzmin, A., Kwon, Y.-J., Lange, J. S., Lee, I. S., Lewis, P., Li, Y., Li Gioi, L., Libby, J., Liventsev, D., Lukin, P., Matvienko, D., Miyabayashi, K., Miyata, H., Mizuk, R., Moll, A., Mori, T., Mussa, R., Nakano, E., Nakao, M., Nanut, T., Natkaniec, Z., Nisar, N. K., Nishida, S., Ogawa, S., Okuno, S., Olsen, S. L.
• Format: Article
• Language: English
• Subjects: PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
• ISSN: 1550-7998; 1550-2368
• DOI: 10.1103/PhysRevD.91.112007

We report here measurement of the cross section of e+e- → π+π-ψ ( 2S ) between 4.0 and 5.5 GeV, based on an analysis of initial state radiation events in a 980fb-1 data sample recorded with the Belle detector. The properties of the Y ( 4360 ) and Y ( 4660 ) states are determined. Fitting the mass spectrum of π+π-ψ ( 2S ) with two coherent Breit-Wigner functions, we discover two solutions with identical mass and width but different couplings to electron-positron pairs: MY ( 4360 ) = ( 4347±6±3 ) MeV / c2 , Γ Y ( 4360 ) = ( 103±9±5 ) MeV , MY ( 4660 ) = ( 4652±10±8 ) MeV / c2 , Γ Y ( 4660 ) = ( 68±11±1 ) MeV ; and B [ Y ( 4360 ) → π+π-ψ ( 2S ) ] · Γ Y ( 4360 ) e+e-= ( 10.9±0.6±0.7 ) eV and B [ Y ( 4660 ) → π+π-ψ ( 2S ) ] · Γ Y ( 4660 ) e+e-= ( 8.1±1.1±0.5 ) eV for one solution; or B [ Y ( 4360 ) → π+π-ψ ( 2S ) ] · Γ Y ( 4360 ) e+e-= ( 9.2±0.6±0.6 ) eV and B [ Y ( 4660 ) → π+π=ψ ( 2S ) ] · Γ Y ( 4660 ) e+e-= ( 2.0±0.3±0.2 ) eV for the other. Here, the first errors are statistical and the second systematic. Evidence for a charged charmoniumlike structure at 4.05GeV / c2 is observed in the π±ψ ( 2S ) intermediate state in the Y ( 4360 ) decays. decays.