2025/08/30 by M. Ablikim, BESIII Collaboration, Ablikim, M. +782
Physics and Astronomy · #Quantum Chromodynamics and Particle Interactions #Nuclear physics research studies #Particle physics theoretical and experimental studies
paper · pdf · doi:10.48550/arxiv.2509.00289
Utilizing 2712.4 ± 14.3 million ψ(3686) events accumulated by the BESIII experiment, we perform a partial wave analysis of ψ(3686)→γχcJ→γΛΛ decay (J=0,1,2). The ratio of the helicity amplitudes with same (++) and opposite (+-) helicity for χc2→ΛΛ decay is determined for the first time to be R_χc2=0.575 ± 0.048 ± 0.018 , with a relative phase angle ΔΦ_χc2 = 0.37 ± 0.15 ± 0.05 ~rad. The parameters of the angular distribution of χc2 are determined to be α_χc2 = -0.211 ± 0.100 ± 0.050 and β_χc2 = -0.039 ± 0.089 ± 0.033 , based on the distribution dN / dcosθ= 1 + α_χc2 cos2θ+ β_χc2 cos4θ. The width of χc0 is determined to be 12.31 ± 0.26 ± 0.12 ~MeV. Additionally, the branching fractions for χcJ → ΛΛ are measured to be (3.662 ± 0.048 ± 0.111) × 10-4, (1.182 ± 0.026 ± 0.042) × 10-4, and (1.704 ± 0.035 ± 0.057) × 10-4 for χc0, χc1 and χc2, respectively, where the first uncertainty is statistical and the second systematic.