A non-relativistic model for the[cc]■ tetraquark

We use a non-relativistic model to study the spectroscopy of a tetraquark composed of [cc]■ in a diquark-antidiquark configuration.By numerically solving the Schr?dinger equation with a Cornell-inspired potential,we separate the four-body problem into three two-body problems.Spin-dependent terms(spin-spin,spin-orbit and tensor)are used to describe the splitting structure of the ■ spectrum and are also extended to the interaction between diquarks.Recent experimental data on charmonium states are used to fix the parameters of the model and a satisfactory description of the spectrum is obtained.We find that the spin-dependent interaction is sizable in the diquark-antidiquark system,despite the heavy diquark mass,and also that the diquark has a finite size if treated in the same way as the ■ systems.We find that the lowest S-wave T 4c tetraquarks might be below their thresholds of spontaneous dissociation into low-lying charmonium pairs,while orbital and radial excitations would be mostly above the corresponding charmonium pair thresholds.Finally,we repeat the calculations without the confining part of the potential and obtain bound diquarks and bound tetraquarks.This might be relevant to the study of exotic charmonium in the quark-gluon plasma.The T 4c states could be investigated in the forthcoming experiments at the LHC and BelleⅡ.

The radiative decay D^(0)→ K^(*0)γ with vector meson dominance

Motivated by the experimental measurements of D0 radiative decay modes, we have proposed a model to study the D0→ K＊0γ decay, by establishing a link with D0→ K＊0V （V=ρ0, ω） decays through the vector meson dominance hypothesis. In order to do this properly, we have used the Lagrangians from the local hidden gauge symmetry approach to account for Vγ conversion. As a result, we have found the branching ratio B[D0→ K＊0γ]=（1.55-3.44）×10-4, which is in fair agreement with the experimental values reported by the Belle and BaBar collaborations.