Large non-factorizable contributions in $B \to a_0 a_0$ decays

TL;DR

This paper studies $B o a_0 a_0$ decays using perturbative QCD, revealing large non-factorizable contributions that significantly influence decay rates and CP asymmetries, providing predictions testable at current colliders.

Contribution

First calculation of $B o a_0 a_0$ decays in pQCD showing dominant non-factorizable effects and sizable CP asymmetries, offering new insights into scalar meson dynamics.

Findings

Decay rates of order $10^{-6} o 10^{-5}$ due to non-factorizable contributions

Large direct CP asymmetries around 15-30% predicted

Potential for experimental verification at LHC and Belle-II

Abstract

We investigate three tree-dominated $B \to a_0 a_0$ decays for the first time in the perturbative QCD(pQCD) approach at leading order in the standard model, with $a_0$ standing for the light scalar $a_0(980)$ state, which is assumed as a meson based on the model of conventional two-quark$(q\bar q)$ 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, contrary to the known $B \to \pi \pi$ decays, the $B \to a_0 a_0$ decays are governed by the large non-factorizable contributions, which give rise to the large $B \to a_0 a_0$ decay rates in the order of $10^{-6} \sim 10^{-5}$, although the $a_0$ meson has an extremely small vector decay constant $f_{a_0}$. Also observed are large direct CP-violating asymmetries around $15\%$ and $30\%$ for the $B^0 \to a_0^0 a_0^0$ and $a_0^+ a_0^-$ 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 $a_0$, as well as to complementarily constrain the unitary angle $\alpha$.