E-catalog        

Библиогр.: 38 назв.

Using 106 ×106 ψð3686Þ events collected with the BESIII detector, we measure multipole amplitudes for the decay ψð3686Þ → γχc1;2 → γγJ=ψ beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole (M2) amplitude for ψð3686Þ → γχc1;2 → γγJ=ψ and the normalized electricoctupole amplitudes for ψð3686Þ → γχc2, χc2 → γJ=ψ are determined. The M2 amplitudes for ψð3686Þ → γχc1 and χc1;2 → γJ=ψ are found to differ significantly from zero and are consistent with
theoretical predictions. We also obtain the ratios of M2 contributions of ψð3686Þ and J=ψ decays to χc1;2, b1
2=b2 2 ¼ 1.35 0.72 and a1 2=a2 2 ¼ 0.617 0.083, which agree well with theoretical expectations. By considering the multipole contributions of χc1;2, we measure the product branching fractions for the cascade decays ψð3686Þ → γχc0;1;2 → γγJ=ψ and search for the process ηcð2SÞ → γJ=ψ through ψð3686Þ → γηcð2SÞ. The product branching fraction for ψð3686Þ → γχc0 → γγJ=ψ is 3σ larger than published measurements, while those of ψð3686Þ → γχc1;2 → γγJ=ψ are consistent. No significant signal for the decay ψð3686Þ → γηcð2SÞ → γγJ=ψ is observed, and the upper limit of the product branching fraction at the 90% confidence level is determined.