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

Abstract

In this paper, we calculate the branching ratios and the direct CP-violating asymmetries for decays ${\bar{B}}^0\to a_0^0(980){\pi }^0,a_0^{+}(980){\pi }^{-},a_0^{-}(980){\pi }^{+}$ and $B^{-}\to a_0^0(980){\pi }^{-},a_0^{-}(980){\pi }^0$ 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 $B^{-}\to a_0^0(980){\pi }^{-}$ 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 ${\bar{B}}^0\to a_0^0(980){\pi }^0,B^{-}\to a_0^{-}(980){\pi }^0$ are large, about $(70\sim 80)$, it is still difficult to measure them, since their branching ratios are small, around $(4\sim 5)\times 10^{-7}$.

Comments: 12 pages, 3 figures