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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012, vol. 85, p. -

Two-photon widths of the χ c0,2 states and helicity analysis for χ c2→γγ

Ablikim M., Achasov M. N., Ambrose D. J., An F. F., An Q., An Z. H., Bai J. Z., Ban Y., Becker J., Berger N., Bertani M., Bian J. M., Boger E., Bondarenko O., Boyko I., Briere R. A., Bytev V., Cai X., Calcaterra A., Cao G. F., Chang J. F., Chelkov G., Chen G., Chen H. S., Chen J. C., Chen M. L., Chen S. J., Chen Y., Chen Y. B., Cheng H. P., Chu Y. P., Cronin-Hennessy D., Dai H. L., Dai J. P., Dedovich D., Deng Z. Y., Denig A., Denysenko I., Destefanis M., Ding W. M., Ding Y., Dong L. Y., Dong M. Y., Du S. X., Fang J., Fang S. S., Fava L., Feldbauer F., Feng C. Q., Ferroli R. B., Fu C. D., Fu J. L., Gao Y., Geng C., Goetzen K., Gong W. X., Gradl W., Greco M., Gu M. H., Gu Y. T., Guan Y. H., Guo A. Q., Guo L. B., Guo Y. P., Han Y. L., Hao X. Q., Harris F. A., He K. L., He M., He Z. Y., Held T., Heng Y. K., Hou Z. L., Hu H. M., Hu J. F., Hu T., Huang B., Huang G. M., Huang J. S., Huang X. T., Huang Y. P., Hussain T., Ji C. S., Ji Q., Ji X. B., Ji X. L., Jia L. K., Jiang L. L., Jiang X. S., Jiao J. B., Jiao Z., Jin D. P., Jin S., Jing F. F., Kalantar-Nayestanaki N., Kavatsyuk M., Kuehn W.

Based on a data sample of 106×106 ψ ′ events collected with the BESIII detector, the decays ψ ′→γχ c0,2, χ c0,2→γγ are studied to determine the two-photon widths of the χ c0,2 states. The two-photon decay branching fractions are determined to be B(χ c0→γγ)=(2. 24±0.19±0.12±0.08)×10 -4 and B(χ c2→γγ)=(3.21±0.18±0. 17±0.13)×10 -4. From these, the two-photon widths are determined to be Γ γγ(χ c0)=(2. 33±0.20±0.13±0.17)keV, Γ γγ(χ c2)=(0.63±0.04±0. 04±0.04)keV, and R=Γ γγ(χ c2)/ Γ γγ(χ c0)=0.271±0. 029±0.013±0.027, where the uncertainties are statistical, systematic, and those from the PDG B(ψ ′→γχ c0,2) and Γ(χ c0,2) errors, respectively. The ratio of the two-photon widths for helicity λ=0 and helicity λ=2 components in the decay χ c2→γγ is measured for the first time to be f 0/2=Γγγλ= 0(χ c2)/Γγγλ=2(χ c2)=0. 00±0.02±0.02. © 2012 American Physical Society.