Researchers in Institute of Modern Physics, Chinese Academy Sciences (IMP)  investigated the meson loop contributions to the heavy quarkonium decay and obtained some interesting results.

Researchers estimated the meson loop effects to the heavy quarkonium decay behaviors in an effective Lagrangian approach based on heavy quark limit and chiral symmetry. The decay widths of ψ(4040)/ψ(4160)→J/ψη were evaluated, they found that the results were in good agreement with the experimental measurements from Belle and BESIII Collaboration.

In addition, they also predicted the decay width of ψ(4160)→J/ψη', which may be accessible for further experiments. The radiative transitions between P wave and S wave bottomonia were investigated with meson loop effects. With this effect, the discrepancies between experimental measurements from Belle Collaboration and naive quark model could be resolved.

The decay behaviors of the heavy quarkonim are essential to understanding the non-perturbative property of QCD. Meson loop mechanism, as one non-perturbative QCD mechanism, plays an important role in the investigations of heavy quarkonium decays. 

The related results have been published in Phys. Rev. D87, 054006(2013),Phys. Rev. D87, 094010(2013).

Fig.1 The meson loop contributions to charmonium decay. (Image by IMP)

Fig.2 The meson loop effects to radiative transitions between bottomonia. (Image by IMP)