Large non-factorizable contributions in B → a0a0 decays

Abstract

We investigate three tree-dominated decays for the first time in the perturbative QCD(pQCD) approach at leading order in the standard model, with a0 standing for the light scalar state, which is assumed as a meson based on the model of a conventional two-quark structure. All the topologies of the Feynman diagrams such as the non-factorizable spectator ones and the annihilation ones are calculated in the pQCD approach. It is of great interest to find that, in contrast to the known decays, the decays are governed by the large non-factorizable contributions, which give rise to the large decay rates in the order of , although the a0 meson has an extremely small vector decay constant . Also observed are large direct CP-violating asymmetries around and for the and modes. These sizable predictions could be easily examined at the running Large Hadron Collider and the near future Super-B/Belle-II experiments. The future precision measurements combined with these pQCD predictions might be helpful to explore the complicated QCD dynamics and the inner structure of the light scalar a0, as well as to complementarily constrain the unitary angle α.