1. Improved measurements of two-photon widths of the $\chi_{cJ}$ states and helicity analysis for $\chi_{c2}\to\gamma\gamma$
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BESIII Collaboration, Ablikim, M., Achasov, M. N., Ahmed, S., Albrecht, M., Amoroso, A., An, F. F., An, Q., Bai, J. Z., Bai, Y., Bakina, O., Ferroli, R. Baldini, Ban, Y., Bennett, D. W., Bennett, J. V., Berger, N., Bertani, M., Betton i, D., Bian, J. M., Bianchi, F., Boger, E., Boyko, I., Briere, R. A., Cai, H., Cai, X., Cakir, O., Calcaterra, A., Cao, G. F., Cetin, S. A., Chai, J., Chang, J. F., Chelkov, G., Chen, G., Chen, H. S., Chen, J. C., Chen, M. L., Chen, S. J., Chen, X. R., Chen, Y. B., Chu, X. K., Cibinetto, G., Dai, H. L., Dai, J. P., Dbeyssi, A., Dedovich, D., Deng, Z. Y., Denig, A., Denysenko, I., Destefanis, M., De Mori, F., Ding, Y., Dong, C., ng, J. Do, Dong, L. Y., Dong, M. Y., Dorjkhaidav, O., Dou, Z. L., Du, S. X., Duan, P. F., Fang, J., Fang, S. S., Fang, X., Fang, Y., Farinelli, R., Fava, L., Fegan, S., Feldbauer, F., Felici, G., Feng, C. Q., Fioravanti, E., Fritsch, M., Fu, C. D., Gao, Q., Gao, X. L., Gao, Y., Gao, Y. G., Gao, Z., Garzia, I., Goetzen, K., Gong, L., Gong, W. X., Gradl, W., Greco, M., Gu, M. H., Gu, S., Gu, Y. T., Guo, A. Q., Guo, L. B., Guo, R. P., Guo, Y. P., Haddadi, Z., Han, S., Hao, X. Q., Harris, F. A., He, K. L., He, X. Q., Heinsius, F. H., Held, T., Heng, Y. K., Holtmann, T., Hou, Z. L., Hu, C., Hu, H. M., Hu, T., Hu, Y., Huang, G. S., Huang, J. S., Huang, X. T., Huang, X. Z., Huang, Z. L., Hussain, T., Andersson, W. Ikegami, Ji, Q., Ji, Q. P., Ji, X. B., Ji, X. L., Jiang, X. S., Jiang, X. Y., Jiao, J. B., Jiao, Z., Jin, D. P., Jin, S., Jin, Y., Johansson, T., Julin, A., alantar-Nayestanaki, N. K, Kang, X. L., Kang, X. S., Kavatsyuk, M., Ke, B. C., Khan, T., Khoukaz, A., Kiese, P., Kliemt, R., Koch, L., Kolcu, O. B., Kopf, B., Kornicer, M., Kuemmel, M., Kuhlmann, M., Kupsc, A., Kühn, W., Lange, J. S., Lara, M., Larin, P., Lavezzi, L., Leithoff, H., Leng, C., Li, C., Li, Cheng, Li, D. M., Li, F., Li, F. Y., Li, G., Li, H. B., Li, H. J., Li, J. C., Li, Jin, Li, K., Li, K. J., Li, Lei, Li, P. L., Li, P. R., Li, Q. Y., Li, T., Li, W. D., Li, W. G., Li, X. L., Li, X. N., Li, X. Q., Li, Z. B., Liang, H., Liang, Y. F., Liang, Y. T., Liao, G. R., Lin, D. X., Liu, B., Liu, B. J., Liu, C. X., Liu, D., Liu, F. H., Liu, Fang, Liu, Feng, Liu, H. B., Liu, H. H., Liu, H. M., Liu, J. B., Liu, J. P., Liu, J. Y., Liu, K., Liu, K. Y., Liu, Ke, Liu, L. D., Liu, P. L., Liu, Q., Liu, S. B., Liu, X., Liu, Y. B., Liu, Y. Y., Liu, Z. A., Liu, Zhiqing, Long, Y. F., Lou, X. C., Lu, H. J., Lu, J. G., Lu, Y., Lu, Y. P., Luo, C. L., Luo, M. X., Luo, X. L., Lyu, X. R., Ma, F. C., Ma, H. L., Ma, L. L., Ma, M. M., Ma, Q. M., Ma, T., Ma, X. N., Ma, X. Y., Ma, Y. M., Maas, F. E., Maggiora, M., Malik, Q. A., Mao, Y. J., Mao, Z. P., Marcello, S., Meng, Z. X., Messchendorp, J. G., Mezzadri, G., Min, J., Min, T. J., Mitchell, R. E., Mo, X. H., Mo, Y. J., Morales, C. Morales, Morello, G., Muchnoi, N. Yu., Muramatsu, H., Musiol, P., Mustafa, A., Nefedov, Y., Nerling, F., Nikolaev, I. B., Ning, Z., Nisar, S., Niu, S. L., Niu, X. Y., Olsen, S. L., Ouyang, Q., Pacetti, S., Pan, Y., Patter i, P., Pelizaeus, M., Pellegrino, J., Peng, H. P., Peters, K., Pettersson, J., Ping, J. L., Ping, R. G., Poling, R., Prasad, V., Qi, H. R., Qi, M., Qian, S., Qiao, C. F., Qin, J. J., Qin, N., Qin, X. S., Qin, Z. H., Qiu, J. F., Rashid, K. H., Redmer, C. F., Richter, M., Ripka, M., Rolo, M., Rong, G., Rosner, Ch., Ruan, X. D., Sarantsev, A., Savrié, M., Schnier, C., Schoenning, K., Shan, W., Shao, M., Shen, C. P., Shen, P. X., Shen, X. Y., Sheng, H. Y., Song, J. J., Song, X. Y., Sosio, S., Sowa, C., Spataro, S., Sun, G. X., Sun, J. F., Sun, L., Sun, S. S., Sun, X. H., Sun, Y. J., Sun, Y. K, Sun, Y. Z., Sun, Z. J., Sun, Z. T., Tang, C. J., ng, G. Y. Ta, Tang, X., Tapan, I., Tiemens, M., Tsednee, B. T., Uman, I., Varner, G. S., Wang, B., Wang, B. L., Wang, D., Wang, D. Y., Wang, Dan, Wang, K., Wang, L. L., Wang, L. S., Wang, M., Wang, P., Wang, P. L., Wang, W. P., Wang, X. F., Wang, Y. D., Wang, Y. F., Wang, Y. Q., Wang, Z., Wang, Z. G., Wang, Z. H., Wang, Z. Y., Weber, T., Wei, D. H., Weidenkaff, P., Wen, S. P., Wiedner, U., Wolke, M., Wu, L. H., Wu, L. J., Wu, Z., Xia, L., Xia, Y., Xiao, D., Xiao, H., Xiao, Y. J., Xiao, Z. J., Xie, Y. G., Xie, Y. H., Xiong, X. A., Xiu, Q. L., Xu, G. F., Xu, J. J., Xu, L., Xu, Q. J., Xu, Q. N., Xu, X. P., Yan, L., Yan, W. B., Yan, W. C., an, Y. H. Y, Yang, H. J., Yang, H. X., Yang, L., Yang, Y. H., Yang, Y. X., Ye, M., Ye, M. H., Yin, J. H., You, Z. Y., Yu, B. X., Yu, C. X., Yu, J. S., Yuan, C. Z., Yuan, Y., Yuncu, A., Zafar, A. A., Zeng, Y., Zeng, Z., ang, B. X. Zh, Zhang, B. Y., Zhang, C. C., Zhang, D. H., Zhang, H. H., Zhang, H. Y., Zhang, J., Zhang, J. L., Zhang, J. Q., Zhang, J. W., Zhang, J. Y., Zhang, J. Z., Zhang, K., Zhang, L., Zhang, S. Q., Zhang, X. Y., Zhang, Y., Zhang, Y. H., Zhang, Y. T., Zhang, Yu, Zhang, Z. H., Zhang, Z. P., Zhang, Z. Y., Zhao, G., Zhao, J. W., Zhao, J. Y., Zhao, J. Z., Zhao, Lei, Zhao, Ling, Zhao, M. G., Zhao, Q., Zhao, S. J., Zhao, T. C., Zhao, Y. B., Zhao, Z. G., Zhemchugov, A., Zheng, B., Zheng, J. P., Zheng, W. J., Zheng, Y. H., Zhong, B., Zhou, L., Zhou, X., Zhou, X. K., Zhou, X. R., Zhou, X. Y., Zhou, Y. X., Zhu, J., Zhu, K., Zhu, K. J., Zhu, S., Zhu, S. H., Zhu, X. L., Zhu, Y. C., Zhu, Y. S., Zhu, Z. A., Zhuang, J., Zotti, L., Zou, B. S., and Zou, J. H.
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High Energy Physics - Experiment - Abstract
Based on $448.1 \times 10^6$ $\psi(3686)$ events collected with the BESIII detector, the decays $\psi(3686)\to\gamma\chi_{cJ}, \chi_{cJ} \to \gamma\gamma~(J=0, 1, 2)$ are studied. The decay branching fractions of $\chi_{c0,c2} \to \gamma\gamma$ are measured to be $\mathcal{B}(\chi_{c0}\to\gamma\gamma) = (1.93 \pm 0.08 \pm 0.05 \pm 0.05)\times 10^{-4}$ and $\mathcal{B}(\chi_{c2}\to\gamma\gamma) = (3.10 \pm 0.09 \pm 0.07 \pm 0.11)\times 10^{-4} $, which correspond to two-photon decay widths of $\Gamma_{\gamma\gamma}(\chi_{c0}) = 2.03 \pm 0.08 \pm 0.06 \pm 0.13 ~\rm{keV}$ and $\Gamma_{\gamma\gamma}(\chi_{c2}) = 0.60 \pm 0.02 \pm 0.01 \pm 0.04 ~\rm{keV}$ with a ratio of $\mathcal{R}=\Gamma_{\gamma\gamma}(\chi_{c2})/\Gamma_{\gamma\gamma}(\chi_{c0})= 0.295 \pm 0.014 \pm 0.007 \pm 0.027$, where the uncertainties are statistical, systematic and associated with the uncertainties of $\mathcal{B}(\psi(3686)\to\gamma\chi_{c0,c2})$ and the total widths $\Gamma(\chi_{c0,c2})$, respectively. For the forbidden decay of $\chi_{c1}\to\gamma\gamma$, no signal is observed, and an upper limit on the two-photon width is obtained to be $\Gamma_{\gamma\gamma}(\chi_{c1})<5.3 ~\rm{eV}$ at the 90\% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay $\chi_{c2}\to\gamma\gamma$ is also measured to be $f_{0/2} = \Gamma^{\lambda=0}_{\gamma\gamma}(\chi_{c2})/\Gamma^{\lambda=2}_{\gamma\gamma}(\chi_{c2}) = (0.0 \pm 0.6 \pm 1.2)\times 10^{-2}$, where the uncertainties are statistical and systematic, respectively., Comment: 11 pages, 4 figures, 4 tables
- Published
- 2017
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