Study of scalar meson $a_0(980)$ from $B \to a_0(980)π$ Decays

In this paper, we calculate the branching ratios and the direct CP-violating asymmetries for decays $\bar{B}^0\to a^0_0(980)π^0, a^+_0(980)π^-, a^-_0(980)π^+$ and $B^-\to a^0_0(980)π^-, a^-_0(980)π^0$ by employing the perturbative QCD factorization approach. Although the light scalar meson $a_0(980)$ is widely perceived as primarily the four-quark bound states, the calculation shows that the 2-quark model supposition for $a_0(980)$ can not be ruled out by the currently available experiment upper limits. In these considered decays, the branching ratio for the $B^-\to a^0_0(980)π^-$ is the largest, $2.8\times 10^{-6}$, while its direct CP asymmetry is the smallest, $\sim 14$. Although the direct CP asymmetries for the decays $\bar{B}^0\to a^0_0(980)π^0, B^-\to a^-_0(980)π^0$ are large, about $(70\thicksim80)$, it is still difficult to measure them, since their branching ratios are small, around $(4\thicksim5)\times 10^{-7}$.

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