Improved measurements of two-photon widths of the χcJ states and helicity analysis for χc2 →γγ M. Ablikim, M. N. Achasov, S. Ahmed [et al.]
Material type: ArticleSubject(s): BESIII, детектор | BEPCII, коллайдерGenre/Form: статьи в журналах Online resources: Click here to access online In: Physical Review D Vol. 96, № 9. P. 092007-1-092007-11Abstract: Based on 448.1×106 ψ(3686) events collected with the BESIII detector, the decays ψ(3686)→γχcJ,χcJ→γγ(J=0,1,2) are studied. The decay branching fractions of χc0,2→γγ are measured to be B(χc0→γγ)=(1.93±0.08±0.05±0.05)×10−4 and B(χc2→γγ)=(3.10±0.09±0.07±0.11)×10−4, which correspond to two-photon decay widths of Γγγ(χc0)=2.03±0.08±0.06±0.13 keV and Γγγ(χc2)=0.60±0.02±0.01±0.04 keV with a ratio of R=Γγγ(χc2)/Γγγ(χc0)=0.295±0.014±0.007±0.027, where the uncertainties are statistical, systematic and associated with the uncertainties of B(ψ(3686)→γχc0,2) and the total widths Γ(χc0,2), respectively. For the forbidden decay of χc1→γγ, no signal is observed, and an upper limit on the two-photon width is obtained to be Γγγ(χc1)<5.3 eV at the 90% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay χc2→γγ is also measured to be f0/2=Γλ=0γγ(χc2)/Γλ=2γγ(χc2)=(0.0±0.6±1.2)×10−2, where the uncertainties are statistical and systematic, respectively.Библиогр.: 39 назв.
Based on 448.1×106 ψ(3686) events collected with the BESIII detector, the decays ψ(3686)→γχcJ,χcJ→γγ(J=0,1,2) are studied. The decay branching fractions of χc0,2→γγ are measured to be B(χc0→γγ)=(1.93±0.08±0.05±0.05)×10−4 and B(χc2→γγ)=(3.10±0.09±0.07±0.11)×10−4, which correspond to two-photon decay widths of Γγγ(χc0)=2.03±0.08±0.06±0.13 keV and Γγγ(χc2)=0.60±0.02±0.01±0.04 keV with a ratio of R=Γγγ(χc2)/Γγγ(χc0)=0.295±0.014±0.007±0.027, where the uncertainties are statistical, systematic and associated with the uncertainties of B(ψ(3686)→γχc0,2) and the total widths Γ(χc0,2), respectively. For the forbidden decay of χc1→γγ, no signal is observed, and an upper limit on the two-photon width is obtained to be Γγγ(χc1)<5.3 eV at the 90% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay χc2→γγ is also measured to be f0/2=Γλ=0γγ(χc2)/Γλ=2γγ(χc2)=(0.0±0.6±1.2)×10−2, where the uncertainties are statistical and systematic, respectively.
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