Decays of the J/ψ resonance into the three-photon final state are investigated. Branching ratios for the decays of J/ψ→γπ0 and J/ψ→γη' are determined to be Br(J/ψ→γπ0)=(4.6±1.1)×10-5 and Br(J/ψ→γη')=(4.12±0.82)—10-3. The ratio of the two decay widths, Γ(J/ψ→γη')/Γ(J/ψ→γη),is 4.79±0.85. This value agrees weM with the predictions of the two theoretical models.

The mean multiplicities of mesons π±, π0, K±, Ks0, K*0, K*±, and φ and baryons p, Ξ±, and ∑± (1385) are measured for the first time at J/ψ region with 200,000 events collected at the BEPC with the BES detector. The results are compatible with LUND and Shandong phenomenological models. Based on the experimental results, the strangeness suppression factor s/u and spin suppression factor V(V+P) can be calculated to be ~0.3 and ~0.3-0.5, respectively, which are in good agreement with those given by the ARGUS Collaboration in the Υ region. This indicates that the SU(6) breaking is consistent in the energy region from J/ψ to Υ.

本文基于北京正负电子对撞机（BEPC）上北京谱仪（BES）所收集到的2.5×10 6 J/ψ,重建刻度后的事例,研究了强子衰交道J/ψ→ωf 2 （1270）,f 2 （1270）→π + π - 所揭示出的共振态f 2 （1270）的性质,测量了它的质量、宽度和分支比,利用最大似然法对角分布进行了拟合,给出自旋宇称为2 ++ ,首次得到螺旋度振幅比为x=0.99±0.29;y=0.24±0.17;z 1 =0.90±0.57;z 2 =0.56±0.22.