Isospin violation in ϕ,J/ψ,ψ′→ωπ0\phi, J/\psi, \psi^\prime \to \omega \pi^0 via hadronic loops

In this work, we study the isospin-violating decay of $\phi\to \omega\pi^0$ and quantify the electromagnetic (EM) transitions and intermediate meson exchanges as two major sources of the decay mechanisms. In the EM decays, the present datum status allows a good constraint on the EM decay form factor in the vector meson dominance (VMD) model, and it turns out that the EM transition can only account for about $1/4\sim 1/3$ of the branching ratio for $\phi\to \omega\pi^0$. The intermediate meson exchanges, $K\bar{K}(K^*)$ (intermediate $K\bar{K}$ interaction via $K^*$ exchanges), $K\bar{K^*}(K)$ (intermediate $K\bar{K^*}$ rescattering via kaon exchanges), and $K\bar{K^*}(K^*)$ (intermediate $K\bar{K^*}$ rescattering via $K^*$ exchanges), which evade the naive Okubo-Zweig-Iizuka (OZI) rule, serve as another important contribution to the isospin violations. They are evaluated with effective Lagrangians where explicit constraints from experiment can be applied. Combining these three contributions, we obtain results in good agreement with the experimental data. This approach is also extended to $J/\psi(\psi^\prime)\to \omega\pi^0$, where we find contributions from the $K\bar{K}(K^*)$, $K\bar{K^*}(K)$ and $K\bar{K^*}(K^*)$ loops are negligibly small, and the isospin violation is likely to be dominated by the EM transition.Comment: Revised version resubmitted to PRD; Additional loop contributions included; Conclusion unchange

Heavy Quark Spin Symmetry Violating Hadronic Transitions of Higher Charmonia

In heavy quarkonia, hadronic transitions serve as an enlightened probe for the structure and help to establish the understanding of light quark coupling with a heavy degree of freedom. Moreover, in recent years, hadronic transitions revealed remarkable discoveries to identify the new conventional heavy quarkonia and extracting useful information about the so called "XYZ" exotic states. In this contribution, we present our predictions for heavy quark spin symmetry (HQSS) breaking hadronic transitions of higher $S$ and $D$ wave vector charmonia based on our recently proposed model (inspired by Nambu-Jona-Lasinio (NJL) model) to create light meson(s) in heavy quarkonium transitions. We also suggest spectroscopic quantum numbers $(^{2S+1}L_J)$ for several observed charmoniumlike states. Our analysis indicates that the $Y(4360)$ is most likely to be a $3D$ dominant state.Comment: Proceedings of the talk presented at "XVII International Conference on Hadron Spectroscopy and Structure (Hadron2017)", 25-29 September 2017, Salamanca, Spai

How the X(5568) challenges our understanding of QCD

We discuss the X(5568) particle recently announced by the D0 Collaboration. Several types of models were proposed to explain this structure in the literature. As pointed out by Burns and Swanson (arXiv:1603.04366), none of them provides a satisfactory description of the observation. We provide additional arguments using general properties of QCD, and conclude that the observation of the X(5568), if confirmed, poses serious challenges to our understanding of nonperturbative QCD.Comment: 5 pages. Typos removed, a wrong statement corrected, conclusions unchanged; the LHCb preliminary result mentioned at the en