2025/05/29 by Geng Li, Li, Geng, Chunjiang Shi +5
Physics and Astronomy · #Quantum Chromodynamics and Particle Interactions #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies
paper · pdf · doi:10.48550/arxiv.2505.23220
We investigate the JPC=(0,2)++ ηc ηc and J/ψJ/ψ scatterings in Nf=2 lattice QCD at two pion masses mπ≈ 420 MeV and 250 MeV. The quark field smearing scheme used in the distillation method strongly suppresses high-momentum states, thereby limiting the maximum accessible center-of-mass energy in this study to approximately 6.6 GeV. Given the observed near-decoupling of the ηcηc and J/ψJ/ψ channels, we analyze their scattering properties using the single-channel Lüscher's method. In 0++ channels, ηcηc and J/ψJ/ψ have repulsive and attractive interactions, respectively, which are dominated by the quark exchange effects with the Fierz rearrangement determining the interaction characteristic. A likely 0++ virtual state is observed below the threshold by 20-40 MeV in the 1S0 J/ψJ/ψ scattering and may have connection with X(6200). In 2++ channels, the near-threshold interaction for the 5S2 J/ψJ/ψ scattering is repulsive. The di-charmonium interactions are found to be insensitive to mπ and can be consistently understood in terms of quark rearrangement effects combined with a one-gluon-exchange mechanism, both of which are supported by our lattice QCD results. Most importantly, we observe a 2++ resonance in the 5S2 J/ψJ/ψ scattering, whose properties are (mR,ΓR)=(6544(10),552(34)) MeV for mπ≈ 420 MeV and (6539(13),546(57)) MeV for mπ≈ 250 MeV, which are compatible with the parameters of the fully-charmed broad structure X(6600) (or X(6400)) reported by ATLAS and CMS.